Operating a hot isostatic press? The stages for HIP processing can become faster and more effective with gas detection technology. Learn about real-time leak detection analysis and continuous monitoring for outgassing.
ThisTechnical Tuesdayarticle byErik Cox, manager of New Business Development at Gencoa, was originally published inHeat Treat Today’sMarch/April 2024 Aerospaceprint edition.
The Problem in HIP
Hot isostatic pressing (HIP) is a widely employed method for densifying powders or cast and sintered parts. It involves subjecting materials to extreme conditions — high pressure (100–200 MPa) and high temperature (typically 1652°F–2282°F, or 900–1250°C) — in a specialized vessel.
Contact us with your Reader Feedback!Figure 1. Pumping times based on residual water vapor
One aspect of HIP comes before introducing metal or ceramic powders to the vessel: Operators must test for any leaks in the canisters. This ensures that the proper HIP processing can be completed. Secondly, outgassing of the powder must be performed, and thirdly, outgassing the HIP chamber should be done. All three are essential steps that are typically time consuming and inefficient, but new gas detection technology can make this pre-processing stage faster and more effective.
Real-Time Analysis for Leak Detection
Leak detection is normally performed with a helium leak detector, which are expensive and require significant technical knowledge to operate. Some HIP processing providers simply forego leak checking of the canister, fill the HIP canister with powder, and perform the degas; but in this case, any leaks will be identified during the degas process, and powder must then be removed to repair the canister.
HIP users must look to technology that effectively detects leaks before they proceed to outgassing. One example of this is Gencoa’s Optix gas sensor: As the pumping procedure commences and pressure reaches 0.5 mbar (which typically occurs within 15–30 seconds), the device switches on and employs a sophisticated analysis of the nitrogen that enters the canister from the atmosphere to discern the leak rate of the canisters. When a leak is detected, argon gas can be sprayed around the canister to accurately detect the leak point and allow repair.
Outgassing: Traditional vs. Continuous Monitoring
Outgassing is a critical step in the preconditioning of powders for HIP processed components, involving the removal of adsorbed gases and water vapor from the metal powder through vacuum pumping. Traditionally, the endpoint for this process is not monitored, leading to an overly long vacuum pumping stage of up to several days to ensure that the powders are correctly prepared.
Th is challenge is addressed by providing continuous monitoring throughout the entire degassing process, reducing the time to degas through the ability of the Gencoa Optix gas sensor to precisely determine the degas endpoint.
Figure 2. Gencoa Optix
By offering real-time feedback and notifying users when degassing is complete, this sensor saves time and ensures the production of high-quality components with traceability. With the Optix, one user saw their degas times reduced from 24 hours to 4 hours. The sensor is capable of residual gas analysis, providing a comprehensive solution for improved productivity. Its wide-range pressure measurement capabilities, coupled with efficient leak checking of HIP processing enclosures, further enhance the overall operational efficiency.
Optix operates as a highly sensitive, stand-alone device that utilizes a small plasma (“light”) that detects the gas species present. This design ensures that the detector remains impervious to contamination or vacuum issues, maintaining continuous monitoring and avoiding potential damage. Because the device also eliminates the need for filament replacement or disassembly of components for maintenance, the design will perform at 100% operational uptime even in the harshest environments.
Indispensable Tools for HIP Processing
HIP operators need to maintain equipment efficiently and effectively, and technologies that integrate solutions not only enhance overall productivity, leak detection, and control of the degassing process, but are indispensable to improving the overall quality and traceability of components. Leveraging technologies that allow for early detection and increase uptime will only enhance the future HIP can offer to the AM-focused aerospace industry.
About the Author
Erik Cox, Manager of New Business Development, Gencoa
Dr. Erik Cox is a former research scientist with experience working in the U.S., Singapore, and Europe. Erik has a master’s degree in physics and a PhD from the University of Liverpool. As the manager of New Business Development at Gencoa, Erik plays a key role in identifying industry sectors outside of Gencoa’s traditional markets that can benefit from the company’s comprehensive portfolio of products and know-how.
For more information:
Contact Erik at sales@gencoa.com
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Dive into the role and benefits of HIP and HPHT™ in the space industry, highlighting how these key processes are shaping the future of space applications.
ThisTechnical Tuesdayarticle by Andrew Cassese, applications engineer, Quintus Technologies was originally published inHeat Treat Today’sMarch/April 2024 Aerospaceprint edition.
The realm of space exploration and technology is rapidly evolving, pushing the boundaries of what’s possible in engineering and material science. Among the key players in this revolutionary change are hot isostatic pressing (HIP) and High Pressure Heat Treatment™ (HPHT™). These processes have become indispensable in manufacturing components that can withstand the harsh conditions of space. In this demanding environment, the longevity and reliability of components are paramount.
Reducing Risk
Space missions have put increasing focus on the need to minimize risk and improve mission safety. Some well-documented, safety-related events include:
Outer space
Soyuz 11 decompression in 1971
Earth’s atmosphere
Soyuz 1 parachute failure in 1967
X-15 controls failure in 1967
Space Shuttle Challenger launch booster failure in 1986
Space Shuttle Columbia re-entry disaster in 2003
Structural integrity is therefore in focus for every single component involved in space missions, with exacting demands on quality and function. Material failure is not an option, and therefore component qualification is one of the main areas of focus. Predictable properties that are reliable and with minimal variation are critical for mission safety. Hot isostatic pressing helps to guarantee this by reducing the spread and variation in mechanical properties.1 It works to do this by using high temperatures and pressures to close internal defects in mission critical parts after casting or additive manufacturing. This increases the density of components and gives them a more anisotropic microstructure which in turn results in more consistent mechanical properties.2
What Properties Are Most Important
The harsh environment of space demands components with exceptional properties. They must withstand extreme temperatures, resist radiation, endure vacuum pressures, and cope with mechanical stress from vibrations and accelerations. HIP processing plays a pivotal role in this, enhancing material properties to meet these challenges. Space manufacturers also must think about thermal expansion/contraction due to temperature variations, compressive stresses, irradiation, and space debris. All of these can affect mission success and can ultimately prevent loss of life, see Figure 1.
Figure 1. Challenges that space-bound materials must endure
Through HIP, components gain increased fatigue life, improved ductility, and enhanced fracture toughness, which are crucial for surviving in space.
Common Materials and HIP Processing Requirements
Materials commonly processed by HIP for space applications include titanium, aluminum alloys, nickel-based superalloys, refractory alloys, shape memory alloys, and ceramics. High-strength aluminum and titanium alloys are used due to their high strength to weight ratio which is key for space missions to conserve fuel efficiency, increase payload capacity, and improve maneuverability.3 Nickel-based superalloys are used in exhaust valves and turbine rotors due to their exceptional creep resistance properties at high temperatures. Refractory alloys like Nb-C103 and TZM are used in high-performance rocket nozzles because of their high melting point and excellent strength at high temperatures. Newer shape memory alloys developed by NASA can recuperate their original shape when heating above specific critical temperatures, and their applications are expanding beyond just actuators.4
As new alloys and materials are developed in the space industry, certifications and standards are necessary for their adoption. HIP effectively eliminates porosity in these materials, ensuring structural integrity and performance under the extreme conditions of space. This means HIP recipes need to be developed and optimized for materials to be tested with their greatest potential in mind.
Collaborations with universities and national labs on projects at low TRLs will help set the foundation for HIP in the space industry. Quintus Technologies, through its application centers, is actively engaged in research to further enhance the capabilities of HIP for space applications. Optimizing the HIP process to reduce costs and improve efficiency through HPHT is one area where the company has already found success, see Figures 2 and 3.
Figure 2. Typical thermal processes for additively manufactured partsFigure 3. High pressure heat treatment with solution heat treatment
(SHT) process for the same parts, using an integrated heat
treatment approach
The HPHT process can combine stress relief, solution annealing, HIP, and aging into one cycle. Aft er a ramp up in pressure and temperature, the part is held for a specified amount of time before being rapidly cooled in the URC furnace. Aft er this, the temperature of the machine can be brought up to the aging temperature of the material for the completion of an in situ heat treatment.
A Space Case – Launcher Engine-2 Rocket Engine
Table 1. CuCrZr vs. GRCop-42: A Comparison
One application of this is on the Launcher Engine-2 (E-2) rocket engine.
Quintus Technologies, EOS Group, and Launcher worked together to develop a tailored HPHT cycle for Launcher’s 3D printed E-2, first vetted out in an applications center at small scale. The powder alloy in question, CuCrZr, was developed by EOS and printed on an AMCM M4K machine. EOS compared CuCrZr to the NASA alloy of GRCop-42 and found that the CuCrZr alloy was a more economically viable solution for thermal applications with lower strength requirements, see Table 1. The rapid cooling at 200°C/min in the QIH 122 URC furnace at Aalberts surface technologies allowed the team to HIP and solution heat treat the CuCrZr combustion chamber in a single step. The aging treatment was also performed in the QIH 122 directly aft er the solution.5
In October 2020, a full-scale test firing of the E-2 injector and combustion chamber was conducted at the Launcher NASA Stennis Space Center test stand. On April 21, 2022, Launcher’s E-2 liquid rocket engine was able to demonstrate full thrust. Continued tests from Launcher have been successful with performance boost testing and the first fully integrated engine was ready for shipping on October 12, 2023.6
As humanity reaches further into the cosmos, the role of HIP and HPHT in manufacturing space-bound components becomes increasingly significant. These processes not only enhance the essential properties of materials for space applications but also address the unique challenges of manufacturing for an environment as hostile as space. With ongoing research and development, HIP and HPHT continue to evolve, promising to unlock new possibilities in space exploration and technology, and their contribution will ensure the success of space missions, safeguarding the lives of those who venture into the final frontier.
Figure 5. Test firing of the High Pressure Heat Treated Launcher Engine 2 produced using additive manufacturing
References
[1] Dominik Ahlers and Thomas Tröster, “Performance Parameters and HIP Routes for Additively Manufactured Titanium Alloy Ti6Al4V. EuroPM,” 2019. https://www.semanticscholar.org/paper/Performance-Parameters-and-HIP-Routes-fortitanium- Ahlers-Tr%C3%B6ster/faeb46e6eb8ef3e30bc00b91cd1bd8a7c0619200. [2] Jake T. Benzing et al., “Enhanced strength of additively manufactured Inconel 718 by means of a simplified heat treatment strategy,” Journal of Materials Processing Technology 322, (December 2023). https://www.sciencedirect.com/science/article/abs/pii/S0924013623003424?via%3Dihub. [3] “Engineering Materials for Space Building Stronger Lighter Structures,” Utilities One, last modified November 2023. https://utilitiesone.com/engineering-materials-for-space-building-stronger-lighter-structures. [4] Girolamo Costanza and Maria Elisa Tata, “Shape Memory Alloys for Aerospace, Recent Developments, and New Applications: A Short Review,” Materials (Basel) 13, no. 8 (April 2020): 1856. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7216214/. [5] Mahemaa Rajasekar, “Processing Copper Alloys with Powder Bed Fusion,” LinkedIn, last modified November 2022. https://www.linkedin.com/pulse/processing-copper-alloys-dmls-technology-mahemaarajasekaran/. [6] LAUNCHER (@launcher), “The first fully integrated E-2 engine is ready for shipping to @NASAStennis for our upcoming full engine test campaign later this year. E-2 is a 22,000 lb. (10 ft) thrust LOX/Kerosene,” X post, October 12, 2023. https://twitter.com/launcher/status/1712636548997607752.
About the Author
Andrew Cassese, Applications Engineer, Quintus Technologies
Andrew Cassese is an applications engineer at Quintus Technologies. He has a bachelor’s degree in welding engineering from The Ohio State University.
For more information: Read J Shipley, “Hot Isostatic Pressing in Space – Essential Technology to Ensure Mission Safety,” 2020. Contact Andrew at andrew.cassese@quintusteam.com.
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The race to space is in full swing with public and private sector companies staking their claim in this new frontier. And breakthroughs in technology and materials offer the potential to propel humanity to unprecedented distances. Success hinges not only on the ability to discover novel solutions but also on the capacity to prepare those solutions for efficient, large-scale production.
ThisTechnical Tuesdayarticle by Noel Brady of Paulo was originally published inHeat Treat Today’sMarch/April 2024 Aerospaceprint edition.
Space Today: Making Life on Earth Better, Safer, and More Connected
Noel Brady, Metallurgical Engineer, Paulo Source: Paulo
According to NASA, 95% of space missions in the next decade will stay in low Earth orbit (LEO) and geostationary orbit (GEO). Th at means the first wave of commercial activity in space will be largely focused on making life on Earth better.
Several worldwide broadband satellites are already in orbit, offering more consistent, reliable internet signals around the globe. Defense campaigns are using advanced satellite machine learning to improve asteroid and missile detection, along with revolutionary laser technology that has made intersatellite communication possible for the first time — and the travel of information faster. And to help make life in space safe and successful, NASA is developing a scalable network of public GPS receivers for easy, short-range space navigation and tourism.
All this to say, parts are being developed for a wide range of applications, a huge portion of which are being additively manufactured.
Thermal Processing Standards Necessary for AM Adoption
However promising additive manufacturing is for space, the adoption of AM has still been limited due to the lack of standards for proprietary material and 3D printing applications. Many thermal processing experts are joining research institutions and OEMs in the drive to bring AM into mainstream manufacturing with new industry standards and production-ready solutions that help achieve ROI.
The R&D process for discovering these standards can be lengthy and expensive because it requires trial and error. A prototype or small run of parts must be manufactured, then heat treated, and tested for the desired properties. If a test part’s yield strength is not where it should be, for example, then the heat treating recipe is adjusted, perhaps by lowering the temperature and increasing the pressure, and can be tested again on a new batch of parts.
Coach vs. Custom Cycles
In heat treating, there are two different types of cycles, and it’s important to know the difference when you’re working with any commercial heat treater. Coach cycles tend to be more economical because these are shared cycles — existing recipes that are in high demand and run on a regular schedule — with the potential to have multiple clients’ parts in the furnace at once. For example, a heat treater may have a standard titanium coach cycle they run once a day. See Table A for several coach cycles run at Paulo.
Table A. Example of Coach Cycles for Space Alloys
Coach cycles use recipes that were designed for cast parts and have been around since before additive was a viable form of manufacturing. While it’s true that cast parts and AM parts have similarities, such as their high porosity, it doesn’t mean that the recipes are optimal for preparing today’s parts for heavy space applications. That’s where custom cycles come into play.
Custom cycles are ideal for new or proprietary materials that don’t yet have recipes defined or that are not commonly heat treated enough to run on a regular schedule. The distinction between the two is important because not all heat treaters are equipped to run both types. While you may be able to find a coach recipe that gets you close to where you need to be, it certainly may not be optimal, especially for parts that will have a heavy life of service.
Heat treaters with flexibility of custom and coach cycles, along with full-cycle data reporting, offer a high level of control that is vital for helping the industry progress and scale for production. This is also a big reason why some in-house heat treating operations may choose to outsource some of their work: first collaborating with experienced commercial heat treaters to prove the specification for a new part with custom cycles before scaling for production.
Common Cycle Adjustments for AM
There are five primary parameters that can be adjusted in the heat treating of AM parts to achieve the desired results: temperature, pressure, time, cooling rate, and heating rate. For AM parts, adjustments to the temperature and pressure are a go-to for achieving parts with higher yield strength. For example, running a cycle 50°F cooler, but at 5 ksi higher pressure may yield better results.
There may also be certain heating ramp rates and intermediate holds before parts get to the max temperature, to allow for consistent heating and enhance the material properties. The same goes for the cooling process: controlling the rate at which a part cools with specific holding times and intermediate quenches.
Hot Isostatic Pressing, Space, and Additive Manufacturing
Hot isostatic pressing (HIP) combines high temperature and pressure to improve a part’s mechanical properties and performance at extreme temperatures. The sealed HIP vessel provides uniform pressure to bring parts to 100% theoretical density with minimal distortion. The high level of control and uniformity has made HIP the gold standard for AM parts for space.
Similar to cast parts, 3D-printed materials tend to have porous microstructures that can compromise part performance. HIP is the only process that’s able to eliminate these pores without compromising the complex geometries and near-net dimensions that are achieved in the printing process.
Benefits of HIP for space parts include the following:
Better fatigue resistance
Greater resistance to impact, wear, and abrasion
Improved ductility
For this process, Paulo’s Cleveland division is equipped with a Quintus QIH-122 HIP vessel, which is specially modified with additional thermocouples for more precise temperature control and greater data collection. A higher level of accuracy allows us to iterate with confidence and find an efficient path to production-ready development.
One primary benefit of the Quintus QIH-122 HIP is the ability to have faster cooling at a controlled rate, which allows you to heat treat and solution treat in one furnace. This cooling rate allows great efficiency that cannot be seen with other HIP vessels on the market.
It is critical that heat treaters adapt to meet the needs of this fast-evolving industry. Many commercial heat treaters do not yet have the level of data or dynamic cycle offerings necessary and will only run HIP coach cycles with set parameters. In other words, many are not equipped to economically iterate and adapt heat treating recipes for new parts. Without custom cycles, controlled cooling, and a higher level of data, it is impossible to push the boundaries of what’s possible.
Space Parts Requiring Thermal Processing
The future of space travel requires parts that can not only perform under high levels of mechanical pressure and extreme temperatures but are also durable enough for long-range and repeat missions. Heat treatment is a critical step in preparing rocket engine components, among others, for commission. Other space components commonly heat treat treated are:
Volutes
Turbine manifolds
Bearing housings
Fuel inlets
Housings, support housings
Bearing supports
Turbo components
Since the inception of NASA’s Space Shuttle Program, Paulo has treated integral components for launch and propulsion, along with many parts currently in orbit on the International Space Station.
Materials Used in Space Parts
New materials and applications are being explored every day. Proprietary alloy blends bring unique properties and promising potential in the push for stronger, faster, longer-lasting parts. But with unique properties comes the need for unique heat treating processes. Several high-performance superalloys used for space include:
Inconel 718, 625
Titanium (Ti-6Al-4V)
Hastelloy C22
Haynes 214, 282
GRCop Copper
Inconel 718, a championed space alloy, was originally used as a premier casting material before being adopted for AM. This nickel-based material features an extremely high tensile and yield strength that makes it ideal for components taking on a high mechanical load in extreme environments ranging from combustive to cryogenic — making this a natural material to adopt for space in the early days of 3D printing.
Because casting and 3D printing both result in similar porous microstructures, the heat treating process used for Inconel castings could also be adapted. Finding new opportunities within existing alloys like this is a highly efficient way to gain material advantage in today’s race to space.
Noel joined Paulo in 2011 and spent several years as quality manager before stepping into his current role as a metallurgical engineer. Noel holds a bachelor’s degree in engineering and metallurgy materials science, and he is responsible for thermal process development and hot isostatic pressing process development.
For more information: Contact Noel Brady at nbrady@paulo.com or visit this link to download the full space guide from Paulo.
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Cemented carbide is often used interchangeably with other terms in the industry to describe a popular material for tool production. However, the specifics of what makes up a cemented carbide, and how this material can be processed, are not so widely discussed.
In this best of the web article, discover the composition, applications, and processes involved in sintering cemented carbide, as well as how vacuum furnaces play an essential role for this material. You will encounter helpful diagrams and resourceful images depicting each step of the process.
An Excerpt:
“Hard metal, or cemented carbide, refers to a class of materials consisting in carbide particles dispersed inside a metal matrix. In most cases, the carbide of choice is tungsten carbide but others carbide forming element can be added, such as tantalum (in the form of TaC) or titanium (in the form of TiC). The metal matrix, often referred as ‘binder’ (not to be confused with wax and polymers typically used in powder metallurgy) is usually cobalt, but nickel and chromium are also used. This matrix is acting as a ‘cement,’ keeping together the carbide particles (hence the ‘cemented carbide’ definition).”
The appeal of additive manufacturing (AM) for producing orthopedic implants lies in the “ability to design and manufacture complex and customized structures for surgical patients in a short amount of time.” To complement speed of production, learn how an innovative hot isostatic pressing (HIP) application is confronting the challenges of post-processing heat treatments when creating high quality AM medical parts.
Today’s Technical Tuesday article, written by Andrew Cassese, applications engineer; Anders Magnusson, manager of Business Development; and Chad Beamer, senior applications engineer, all from Quintus Technologies, was originally published in Heat Treat Today’sDecember 2023’s Medical and Energy Heat Treat magazine.
AM is playing a significant role in the medical industry. It gives manufacturers the ability to create customized and complex structures for surgical implants and medical devices. Additionally, medical device manufacturers have different material factors to consider – such as biocompatibility, corrosion resistance, strength, and fatigue – when selecting a material for a given application. Each of these factors plays a significant role. It’s no wonder that the most common metallic biomaterials in today’s industry are stainless steels, cobalt-chrome alloys, and titanium alloys (Trevisan et al., 2018).
In this article, learn about the application of Ti6Al4V in the medical industry, as well as ways to address some of the challenges when producing AM medical components.
The Future Demands Orthopedic Implants
Figure 1. Example of AM trabecular structure on a Ti6Al4V
acetabular cup (Source: Quintus Technologies)
The medical market for orthopedic implants is predicted to grow annually by approximately 4% where joint replacement, spine, and trauma sectors are reported to account for more than two-thirds of the market. The largest portion is joint replacement with over a third of global turnover, reaching in excess of 20 million U.S. dollars in 2022 (ORTHOWORLD® Inc., 2023). This confirms an earlier study by Allied Market Research where spine, knee, and hip implants made up over 66% of the entire market, with knee implants leading the way at 26% (Allied Market Research Study, 2022). This fact, combined with the expectation that the global population aged 60+ is predicted to double between 2020 and 2050, adds to the increasing demand on manufacturers to produce better quality and longer lasting orthopedic implants (Koju et al., 2022).
These factors have increased the predicted medical implant market for Ti6Al4V and other common orthopedic materials. Using AM processes such as electron beam melting (EBM) and laser powder beam fusion (L-PBF), manufacturers can produce thin-walled trabecular structures that are fabricated to promote bone ingrowth in a growing market that is in competition with traditional production methods.
Titanium-based alloys have been increasingly used in orthopedic applications due to their high corrosion resistance and a Young’s modulus similar to that of human cortical bone (Kelly et al., 2021). The high strength-to-weight ratio and bioinert-ness of Ti6Al4V has proven it to be an ideal candidate for orthopedic and dental implants. It is a titanium alloy with 6% aluminum and 4% vanadium that has low density, high weldability, and is heat treatable. Ti6Al4V demonstrates good osteointegration properties, which is defined as the structural and functional connection between living bone and the surface of a load carrying medical implant.
Many manufacturers are using L-PBF to create thin-walled complex structures on the surface of the implant. This makes use of the osteointegration properties as the implant integrates itself into the body over time without the need for bone cement (Kelly et al., 2021). Introducing a large metallic foreign body leads to challenges such as promotion of chronic inflammation, infection, and biofilm formation. Instead, porous AM Ti6Al4V implants have a biomimetic design attempt towards natural bone morphology (Koju et al., 2022).
AM Yields Production Solutions for Medical Alloys
The medical industry has been increasing the use of AM over traditional processing methods. AM facilitates weight reduction, material savings, and shortened lead-time due to reduced machining, but these are only a few of the benefits. Improved functionality and patient satisfaction are also key aspects through tailoring of designs to take advantage of AM over traditional forging and casting techniques. Additionally, the costs of machining a strong alloy like Ti6Al4V can be expensive, and any wasted material and time in turn lead to higher cost.
One of the main reasons for the interest in AM is the ability to design and manufacture complex and customized structures for surgical patients in a short amount of time. For example, if a patient needs an implant for surgery, an MRI scan can help reverse engineer a customized implant. Engineers prepare a design of a patient-specific implant according to the patient’s anatomy that is then printed, HIPed, and finished for surgery with a reduced lead time. This is especially important for trauma victims, where the speed of repair can mean the difference between losing a limb or returning to a fully functional life. Cancer victims and those requiring aesthetic surgery to the skull, nose, jaw, etc., can also benefit from this (Benady et al., 2023).
Some of the current challenges with AM titanium in the medical industry are related to the post-processing heat treatments that are required. These treatments can leave an oxide layer on thin-walled structures that is hard to remove by machining or chemical milling. Quintus Purus®, a unique clean-HIP solution, has proven to overcome this challenge and provide clients with a robust solution that both densifies and maintains a clean surface.
When HIP Meets AM
Figure 2. AM Ti6Al4V components HIPed without getter using conventional HIP (left) and Quintus Purus® (right) (Source: Zeda)
HIP is important in the AM world as a post-process that closes porosity and increases fatigue life. For medical implants, high and low cycle fatigue life properties are key as they affect the longevity of the repair. The mechanical strength and integrity are improved significantly by HIPing the implants, reducing the need for further surgery on the same patient. Modern HIP cycles have been developed to further increase this performance. When combined with Quintus Purus®, modern HIP cycles can minimize the thin, oxygen-affected layer that can result from thermal processing on surfaces of high oxygen-affinitive materials, such as titanium.
For Ti6Al4V, this layer is often referred to as alpha-case. The brittle nature of the alpha-case negatively impacts material properties resulting in medical manufacturers requesting their AM parts in the “alpha-case free” state. Alpha-case can be formed during heat treatment. As surfaces of the payload and process equipment are exposed to oxygen at elevated temperatures, they may be oxidized or reduced, depending on the oxide to oxygen partial pressure equilibrium. During heat treatment, evaporating compounds become part of the process atmosphere, and solids are deposited or formed on other surfaces, either as particles or as surface oxides.
For titanium alloys, surface oxides are formed at logarithmic or linear rates, depending on temperature and oxygen partial pressure. At the same time, oxygen can diffuse into the surface to form the brittle alpha-case, which is detrimental to the part’s fatigue performance. Changes of the surface color can often be seen as an indication that surface reactions have occurred during processing when using traditional thermal processes (Magnusson et al., 2023).
The HIP furnace atmosphere contaminants that cause this oxidation can originate from various sources including the process gas, equipment, furnace interior, and, most importantly, the parts to be processed. The payload itself often absorbs moisture from the surrounding atmosphere before being loaded into the furnace, which is subsequently released into the HIP atmosphere during processing. Industrial practice today attempts to solve the issue by wrapping parts in a material such as stainless steel foil or a “getter” that has a high affinity to oxygen protecting the Ti6Al4V component from exposure to large volumes of process gas, thus helping minimize the pickup of the contaminates.
This method adds material, time, and labor to wrap and unwrap parts before and after each HIP cycle. Also, wrapping in getter cannot guarantee cleanliness and may result in some uneven oxidation. This is where the tools of Quintus Purus® are of assistance; these tools allow the user to define a maximum water vapor content that can be accepted in the HIP system before the process starts. The tool utilizes the Quintus HIP hardware together with a newly developed software routine, ensuring that the target water vapor level is met in the shortest time possible. The result is a cleaner payload, without the need to directly wrap components with getter (Magnusson et al., 2023).
Table 2. Results from case study productivity analysis
(Source: Quintus Technologies)Table 1. Input to case study (Source: Quintus Technologies)
Alpha-Case Avoided: Comparing Conventional HIP and Optimized HIP Technologies
Quintus Technologies performed a study with Zeda, Inc. to evaluate Quintus Purus® on L-PBF Ti6Al4V medical implant parts. The study was performed in the Application Center in Västerås, Sweden in a QIH 21 HIP. A conventional HIP cycle was performed as well as an optimized Quintus Purus® HIP cycle, both without the use of getter. No presence of alpha-case was found on the part processed with the Quintus Purus® cycle as shown in Figure 2 below (Magnusson et al., 2023).
Quintus Purus® can be further enhanced with the use of a Quintus custom-made getter cassette supplied as part of the installation, which consumes or competes for the remainder of contaminant gaseous compounds still present in the system after all other measures such as best practice handling, adjustment of gas quality, etc., have been implemented.
Titanium is considered the getter of choice for Quintus Purus® and is included as an optional compact getter cassette placed at the optimum position in the hot zone of the HIP furnace. Although the custom-made getter cassette occupies a small space, its use can significantly increase loading efficiency. The traditional way of individually wrapping components with stainless steel or titanium foil will consume more furnace volume, through reduced packing efficiency, leading to less components per cycle when compared to the Quintus Purus® titanium getter cassette strategy. Using an average spinal implant size of 2 in3 (32 cm3), one can calculate the packing density in a standard HIP vessel assuming two shifts per day and a 90% machine uptime. For example, a Quintus Technologies QIH 60 URC with a hot zone diameter of 16 in (410 mm) and a height of 40 in (1,000 mm) can pack up to 1,280 implants per cycle, with clearances for proper spacing and load plates.
Figure 3. Quintus Technologies QIH 60 URC outfitted with
Quintus Purus® technology (Source: Quintus Technologies)
The typical Ti6Al4V HIP parameters include a soak time of two hours at 1688°F with 14.5 ksi argon pressure (920°C with 100 MPa). Accounting for heat up and cool down time, this HIP cycle can take less than eight hours, allowing two cycles per day on a two-shift work schedule. A typical case of wrapping each component in getter material adds time, cost, resources, and uses up to an estimated 50% of the load capacity. With the increased efficiency enabled by Quintus Purus®, clients have the opportunity to HIP 552,960 spinal implants per year (Tables 2 and Figure 3).
In conclusion, the growing Ti6Al4V market in the medical industry demands innovative developments to keep up with ever-increasing production volumes, whilst quality demands in lean production are becoming more significant. Solutions like the Quintus Purus® will allow manufacturers to have control over the quality of their titanium parts during a HIP cycle. It can be applied to produce alpha-case free components ensuring the optimal performance of orthopedic implants with increased service life.
References Ahlfors, Magnus, Chad Beamer. “Hot Isostatic Pressing for Orthopedic Implants.” (2020): https://quintustechnologies.com/knowledge-center/hiporthopedic-implants/. Allied Market Research Study performed for Quintus Technologies, 2022. Benady, Amit, Sam J. Meyer, Eran Golden, Solomon Dadia, Galit Katarivas Levy. “Patient-specific Ti-6Al-4V lattice implants for critical-sized load-bearing bone defects reconstruction.” Materials & Design 226 (Feb. 2023): https://www.sciencedirect.com/science/article/pii/S0264127523000205?via%3Dihub. Kelly, Cambre N., Tian Wang, James Crowley, Dan Wills, Matthew H. Pelletier, Edward R. Westrick, Samuel B. Adams, Ken Gall, William R. Walsh, “High-strength, porous additively manufactured implants with optimized mechanical osseointegration.” Biomaterials (Dec.2021): 279, https://www.sciencedirect.com/science/article/abs/pii/.
About the Authors
Andrew Cassese is an applications engineer at Quintus Technologies. He has a bachelor’s degree in welding engineering from The Ohio State University.
Anders Magnusson is the business development manager at Quintus Technologies with an MSc in engineering materials from Chalmers University of Technology.
Chad Beamer
Applications Engineer
Quintus Technologies
Chad Beamer is a senior applications engineer at Quintus Technologies, and one of Heat Treat Today’s 40 Under 40 Class of 2023 award winners. He has an MS from The Ohio State University in Materials Science and has worked as a material application engineer with GE Aviation for years and as a technical services manager with Bodycote. As an applications engineer, he manages the HIP Application Center located in Columbus, Ohio, educates on the advancements of HIP technologies, and is involved in collaborative development efforts both within academia and industry.
In the past, manufacturers with in-house heat treat have turned to hot isostatic pressing (HIP) technology to decrease porosity and increase densification in their processed parts. Now, in 2023, is there anything new HIP can offer heat treaters? To find out, Heat TreatToday asked seven HIP equipment suppliers and heat treat users to enlighten us on the world of HIP as it is today.
Enjoy this original content contribution, first released in Heat TreatToday'sMarch 2023 Aerospaceprint edition!
What are the recent, cutting-edge developments in HIP?
Matt Fitzpatrick
Sales Engineer
Engineered Pressure Systems, Inc.
Source: EPSI
Matt Fitzpatrick, sales engineer at Engineered Pressure Systems, Inc., shares, “Self-diagnosing alarms, failures, and power as well as medium consumption savings are key developments in the HIP industry. Enhanced uniform cooling joins with the development of materials (ceramics, metals, insulation fibers) to improve equipment uptime and reduce cycle time. Self-diagnosing alarms may play a key role in HIP’s future. Each HIP control system has alarms to alert when parameters are not met. The future will be in determining why the parameters are not being achieved. For instance, future control systems may be able to diagnose a bad thermocouple, a failed motor solenoid valve, a leaking high pressure valve, etc.
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“Unfortunately, there are not very many HIP systems purchased every year. It takes time to develop this technology. A good example would be the automotive industry: sensors tell technicians exactly where the problem in the vehicle is. As the PLCs and computers become more advanced, the specific software programs that are developed for the HIP system — in conjunction with advancements with sensors in motors, pumps, valves, transducers, meters, and components — will make it easier and less time consuming to develop complex troubleshooting programs.
“To some heat treaters, HIP can be an unnecessary evil, given its expensive, long cycle times. HIP, however, cannot be eliminated, because it is the only process that attains the densification required in the aerospace, medical, and high-performance automotive industries.”
Cliff Orcutt
Vice President
American Isostatic Presses, Inc.
Source: American Isostatic Presses, Inc.
“HIP technology is very mature and reliable,” Cliff Orcutt, VP of American Isostatic Presses, Inc. assures, “however, the cost to use the process is always one major hurdle preventing its use. AIP is working hard to develop lower cost equipment that can still maintain excellent results and bring higher pressure capabilities to the market. We are also expanding our footprint further into the toll HIP arena with similar goals of lower cost and faster turnaround services. Our new facility opening in Columbus, OH, this spring will also provide a world class development resource to help interested manufacturers determine whether the process can be applied to their parts.”
Chad Beamer
Applications Engineer
Quintus Technologies
Quintus Technologies’ Chad Beamer points to the versatility of HIP: “HIP continues to make its mark in many industries by offering a path to consolidate powders and eliminate process related defects for 100% pore and void free material for improved product integrity. With the continued demand for this special process, Quintus Technologies has several key developments driving industry growth due to the expanding functionality of the equipment. The voice of the client consistently demands production efficiency, reduced environmental impact, and improved process reliability. Modern HIP equipment is delivering on this front, creating a promising future for HIP.
“HIP systems equipped with rapid cooling and quenching functionality (URC®/URQ®) are facilitating lean manufacturing with increased productivity by shortening the cooling segment over conventional cooling, while also offering the opportunity to consolidate thermal post processing steps. HIP systems with URC® can cool at rates up to 932°F/min (500°C/min), and compact HIP units with URQ® furnaces are capable of cooling more than 5400°F/min (3,000°C/min). This leads to the opportunity to combine several thermal processing steps into one process performed under pressure. The combined, or integrated, heat treatment approach inside the HIP vessel is known as High Pressure Heat Treatment™ (HPHT™).
“Developments with the controllability of HIP are further expanding the use of HPHT. The cooling rate of the HIP can be steered using thermocouples to set the desired cooling rate from either process gas or component temperature feedback. Steered cooling driven by the component temperature is interesting when considering different thicknesses of parts in the HIP. The machine can therefore autonomously steer the temperature based on the thickest component to achieve desired material properties. See an example of steered cooling from component temperature feedback in the graph above.
“The tailoring of HIP cycles is a new area of development too. Due to the excellent controllability in a modern HIP tailored heating, sustaining, and cooling segments can be programmed and precisely executed. This is an area of interest for materials needing high cooling rates or having a tight tolerance on heating and cooling rate requirements. An excellent example of a tailored HIP cycle can be seen in recent work by Goel et al., at the University West in Sweden (see illustrations above), capturing the possibility to significantly reduce the treatment time for additively manufactured Inconel 718.
“Quintus has also been working to reduce discoloration and oxides on the surface of parts by improving equipment and best practice in terms of clean HIP operations. This is not an easy challenge to overcome. HIP is performed at very high pressures, often above 1000 atmospheres, using high purity Argon gas (>99.99x). Because of the need for additional gas volumes to achieve desired system pressure during regular HIP, the total pressure of contaminants can become high. Despite these challenges it is now possible to produce materials that have a high affinity for oxygen e.g., aluminum, titanium, and chromium, with significantly less oxidation. This can lead to improvement in fatigue and corrosion resistance fulfilling design criteria and gives great opportunities for more sustainable post-HIP.
“Developments with the digitalization of HIP equipment are also playing a role in meeting the demand of the Industry 4.0 mindset. Integration of the equipment into digitalized production lines enables product and process improvements. Digitalization of high-pressure equipment offers many benefits as it creates opportunities to streamline and save time with preventative maintenance tasks, provides valuable insights and trends into the health of the equipment, expands collaboration, improves uptime, and saves cost.”
Humberto Ramos Fernández
Founder and CEO
HT-MX
“In 2023,” Humberto Ramos Fernández, founder and CEO of HT-MX, comments, “HT-MX will continue to establish itself as the main HIP supplier and expert in Latin America. Additionally, with our Honeywell Aerospace approval, we will be pursuing at least three more OEM approvals not only in the aerospace industry but medical and automotive as well.”
Phil Harris
Marketing Manager
Paulo
Phil Harris, marketing manager at Paulo, highlights HIP’s customization: “The primary focus has been on providing customized HIP cycles that either deliver superior mechanical properties for customers or reduce the need for post-HIP to streamline the supply chain and speed up turnaround. We’ve been successful in both and are always looking for opportunities to collaborate on such endeavors.”
Leah Tankersley, marketing manager, Aalberts surface technologies, says, “We added HIP services to our portfolio in 2020. We have two wire-wound HIP vessels, and plan to expand further with a third unit ready to ship from Sweden soon. Each unit boasts the latest HPHT technology. They are equipped with the proprietary Uniform Rapid Cooling (URC) feature. Our HIP technology has the ability to combine stress relief, HIP, solution, and age in a single process. HPHT HIP streamlines the steps involved in material densification and heat treatment. The URC feature enables all processed components to cool uniformly in a controlled environment, resulting in minimal thermal distortion and non-uniform grain growth.”
Doug Puerta
CEO
Stack Metallurgical Group
Source: Stack Metallurgical Group
Doug Puerta responds for Stack Metallurgical Group: “Stack has been active in supporting the advancement of HPHT. Our newest HIP unit, a Quintus QIH-122, includes Uniform Rapid Cooling (URC) technology which enables cooling rates equivalent to what we achieve with traditional gas quenching. This technology not only allows for improved productivity, but also enables the combination of a traditional HIP cycle with stress relieving solution annealing, or even aging, all in one HIP unit.”
In the next five years, what advancements should manufacturers with in-house heat treat operations expect from HIP technology?
“In terms of cycle times,” Matt Fitzpatrick of Engineered Pressure Systems, Inc. says, “HIP systems are limited by how fast materials can be heated and cooled. In the next five years, reduced maintenance, improvements with furnaces and heat shields, and faster cycle times will occur at both the materials and design levels.”
Cliff Orcutt, from American Isostatic Presses, Inc., sees globalization in HIP’s future, “We don’t expect much change other than to see it expanding into new geographic regions and being applied to more products. The main problem affecting our industry is not deficiencies in the HIP equipment or process, but rather how to use it beneficially in a profitable manner. In the next five years I think countries, such as India, will begin to implement it much more widely as the process becomes better known. As more companies implement it their competition must follow to stay on the same page.”
Chad Beamer, from Quintus Technologies, shares the optimistic outlook, “Quintus is witnessing significant growth potential for HPHT, including the addition of this post-process HIP and heat treatment strategy into industry standards. Also, the demand placed by many industries on surface cleanliness requirements to reduce oxidation and discoloration of sensitive material systems will help drive forward clean HIP techniques. These advancements along with delivering new and upgrading existing HIP equipment with machine digitalization will meet the current and future demands placed by the heat treat market and OEMs.”
And what about HIP in Mexico? Humberto Ramos Fernández of HT-MX responds, “Being located in Mexico, the main advances in HIP in our environment will be mostly geared towards near shoring manufacturing for high added value parts. HT-MX´s HIP service is just one example of a high tech and high complexity process being used in Chihuahua to manufacture high end products and thus we expect near shoring to bring in more opportunities for these kinds of parts to be manufactured and assembled in Chihuahua and Mexico.”
Leah Tankersley of Aalberts surface technologies, says, “As a provider of HIP services, we cannot speak to the advancements in HIP technology per se, but we are seeing material advancements and development of new alloys in AM. These advancements will impact HIP cycles and lead to development of more unique cycles for AM that differ from traditional cycles developed for castings. We’re also seeing ASTM International AM Center of Excellence Consortium members from the AM value stream come together to collaborate on standardization of requirements for AM materials data which includes post processing/hot isostatic pressing. We are one of the founding members of this consortium.
“Additionally, we are working with Quintus to beta test their remote assistance fi eld service support through AR equipment and technology.”
Doug Puerta, Stack Metallurgical Group, thinks, “In the next five years, I expect we’ll continue to see aerospace and medical OEMs evaluate and approve HPHT for additional combined-cycle applications. Ultimately, with span time being so important to our customers (and their customers), combining cycles and reducing span is a really big deal.”
What is the #1 thing manufacturers with in-house heat treaters should know about HIP technology right now?
Safety first, says Matt Fitzpatrick at Engineered Pressure Systems, Inc. (EPSI): “Good safety and maintenance programs and experienced operators and technicians are key to a successful HIP system. Confined space rules and regulations, oxygen monitoring, nondestructive testing (NDT) inspections of the vessel assembly components, good maintenance, and end-user HIP plant safety programs are key. Training is provided with every system regardless of whether it’s a HIP system, CIP system, or WIP system. Before delivering a system, EPSI offers training for safety, maintenance, system operation, controls, and system parameters. Then during installation and startup, training occurs. When startup is completed, we offer training at the client’s site. Generally, this is mutually agreed on during the contract phase and delivery.”
“There is not just one thing,” Cliff Orcutt of American Isostatic Presses, Inc. says, “because HIP has so many different applications. For instance, HIP can be used to heal castings, make parts directly from powders, diffusion bond materials together, or pressure infiltrate materials. HIP can be applied to metals, ceramics, composites, and even plastics. I guess really the number one thing they should know is how to contact a reputable HIP company that can provide the information and technology they require.”
Chad Beamer of Quintus Technologies points to HIP’s benefits for both end customers and heat treaters, “Modern HIP units differ significantly from conventional HIP units. The technology has advanced over the decades offering expanded functionality and improved performance. As for all production processes, lean manufacturing is key to improving product quality, minimizing costs, and maximizing productivity. Reducing waste and increasing throughput should always be a focus.
“The addition of modern HIP with HPHT capability and clean HIP functionality as part of the production chain are HIP advancements that will facilitate robust and lean processes through reduction of yield losses, logistics, and quality-related costs. This is not only of strong interest to heat treaters, but also to the end customers in several industries. And with a broad product line of compact, medium, and large HIP capabilities available, commercially in-sourcing the technology to complement other heat treat equipment is now feasible for many companies.”
Humberto Ramos Fernández speaks directly to in-house heat treaters, “In-house heat treaters must know that, although similar, HIP is not heat treatment. Various aspects of the process are similar but there is a learning curve that must be transitioned and experience in heat treat doesn’t necessarily automatically translate into the HIP experience.”
Aalberts’ Leah Tankersley plainly states, “HIP is an expensive investment.”
“Ironically,” says Doug Puerta of Stack Metallurgical Group, “One of the misconceptions is that modern HIP systems offer HPHT as an alternative to general heat treating. The intent of technology is for use when conventional HIP and heat treatment is required for a given application. When HIP is not required, heat treating is performed in a traditional vacuum furnace. The economics don’t really support heat treating in a HIP unit when a HIP segment is not included.”
How is HIP benefiting heat treaters in the industry today?
Matt Fitzpatrick, from Engineered Pressure Systems, Inc., says, “First, we employ heating and cooling software program models to help with cycle times, though cycle time generally depends on the material being processed.”
Fitzpatrick continues, “Loading and unloading a HIP cycle can be time consuming. We have developed tooling that helps operators prepare a HIP cycle and test the thermocouples prior to being loaded into the HIP vessel. In addition to reducing time, this tooling ensures that the load is prepared properly and won’t damage the furnace while it goes into the vessel.”
Cliff Orcutt, American Isostatic Presses, Inc., replies, “We have many clients that use our HIP systems to improve the properties of AM parts, as sintering alone has a limited upper range for density achievement. By utilizing HIP they are able to achieve near theoretical density and remove voids that can degrade performance or affect surface post finishing. In many cases when you have improvement in properties it can allow redesign with less material usage to improve cost efficiency and help the environment.”
Chad Beamer of Quintus Technologies explains, “HIP is a well-established process that has played a role in delivering advanced materials and components since the 1960s. Originally developed as a diffusion bonding process, its use has expanded to the densification of castings and additively manufactured components as well as the consolidation of powder to produce billets of material or complex near net shapes. Several industries benefit from its use today including aerospace, space, power generation, medical, oil and gas, and nuclear to name a few.
“The process offers several benefits related to material performance. One of the main demands for HIP is to eliminate process-related defects in materials for improvement in mechanical properties. Dynamic properties such as fatigue and creep performance are significantly improved, as is ductility and fracture toughness. The elimination of internal defects leads to reduced mechanical property scatter offering more predictive properties. The outcome can offer extension of a component’s lifecycle as well as potential weight-savings and cost reduction. Another benefit of HIP is for the enhancement of surface quality. The absence of internal defects provides a path to produce machined and polished surfaces free of surface connected imperfections for improvement in mechanical properties and corrosion resistance, as well as optical properties for aesthetically critical applications.
“For heat treat service providers there is motivation to invest in HIP capabilities as it provides a natural complement to existing heat treatment equipment often offering a one-stop shop at many facilities. It also broadens the availability and flexibility of HIP and HPHT services to the industry which is an exciting opportunity.
“As for an OEM’s decision to insource HIP, the benefits are broad. The capabilities of modern systems lead to significant reduction in the production cycle time, savings in overall handling and cost, especially with custom HIP cycles. It also provides a path to gain more control of processing techniques with the opportunity to develop novel approaches while improving control of the intellectual property that is developed.”
Humberto Ramos Fernández, HT-MX responds, “For high value parts, such as aerospace engine components, lead times mean money. Being able to reduce, by weeks, the turnaround time for HIP parts in Mexico means that working capital for these parts is significantly reduced allowing our customers to enjoy these savings.”
Paulo’s Phil Harris says, “HIP, in conjunction with customized cycles, is allowing our customers to deliver parts which were previously not possible. Specifically, the ability to meet material property requirements with additive parts. Where traditional HIP cycles (designed for castings) left them short of tensile requirements, we’ve been able to achieve the necessary properties, winning both of us more work in the process. This success in turn drives the adoption of additive manufacturing.”
Leah Tankersley, Aalberts surface technologies adds, “Our customers benefit from the latest HPHT HIP technology to improve the materials characteristics of their parts. HPHT HIP helps clients reach 100% theoretical density after HIP, improve
tensile strength, and improve creep rupture properties.
“Our URC technology allows clients to reduce lead times with the ability to combine stress relief, HIP, solution, and age into one cycle which saves time by reducing the number of individual process steps and handling of parts. If clients choose to not do stress relief in the HIP, stress relief can be done in the vacuum furnaces that are just 50 feet away from the HIP system in our facility.”
Stack Metallurgical Group’s Doug Puerta replies, “We’ve had the good fortune to introduce several of our clients to the benefits of HIP. While HIP has long been mandated in quality critical industries such as aerospace, orthopedic implant, and power generation, there are other applications where significant performance gains can be achieved through HIP.”
For more information, contact the experts:
Matt Fitzpatrick
Sales Engineer, Engineered Pressure Systems, Inc.
mattfi tzpatrick@epsi-highpressure.com
Cliff Orcutt
Vice President, American Isostatic Presses, Inc.
corcutt@aiphip.com
Chad Beamer
Applications Engineer, Quintus Technologies
chad.beamer@quintusteam.com
Heat treating solutions are important for more than keeping an airplane flying in the sky or a bridge suspended above the water. These two examples are high profile, but what about the heat treating solutions that do not zoom through the air or mark the skyline above rivers? In the medical industry, heat treating solutions are often unseen unless something goes wrong.
When it comes to medical implant and device heat treating, what options are available to manufacturers that will benefit patients? What should we know about the heat treating processes that make metal parts functional as knees, hips, and elbows? Find out in this expert analysis from Quintus Technologies and ECM USA, Inc.
This Technical Tuesday article was first published in Heat Treat Today's December 2022 Medical and Energy print edition.
Introduction
Dan McCurdy, former president at Bodycote, Automotive and General Industrial Heat Treatment for North America and Asia, knows full well just how much time, energy, and pain the right medical heat treating practice and alloy composition can save a patient. Dan’s wife suffered from complications due to a nickel allergy in a traditionally thermally-processed ASTM F75 knee implant. She dealt with constant inflammation, swelling, and pain. Physical therapy and a second procedure did nothing to ease the discomfort. The best medicine for Dan’s wife? A specially heat treated medical implant (more of Dan's story can be found at the end of this article).
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To understand the stories behind final medical products, Heat Treat Today asked Quintus Technologies and ECM USA, Inc. to share two different approaches on medical implant and device heat treatment. These two companies at the forefront of the medical heat treating industry shared about hot isostatic pressing (HIP) with additive manufacturing, and vacuum heat treating. Read their answers to our questions and learn how, when it comes to implantable medical devices, heat treating can be the best medicine.
How do you ensure your equipment maintains the precise specifications required in the medical industry? What specifically is necessary to maintain compliance when it comes to medical implants?
Quintus Technologies
Chad Beamer Applications Engineer Quintus Technologies
Quintus Technologies has observed a trend in bringing Nadcap to the medical industry. Historically the medical industry has focused on the standards and regulations for the quality management system of their approved supplier, but a consistent transition to technical aspects of critical processes (including HIPing) is becoming the norm. Quintus Technologies’ background is one of delivering HIP equipment in line with Nadcap and AMS2750 specifications. The medical industry requires best-in-class temperature uniformity and accuracy; systems designed with production driven flexibility (such as thermocouple quick-connectors for T/C sensor installation
to minimize downtime); HIP furnaces equipped with uniform rapid cooling (URC®) for optimized cycle productivity; active involvement in standards committees; and working directly with the industry.
Requirements are increasing in terms of productivity and the introduction of more complex surface requirements. It is crucial to work closely with the industry to reduce oxidation of orthopedic implants during the HIP and heat treatment processes.
Steering of the HIP cycle is key, along with in-HIP heat treatments to achieve the desired microstructure for the application, which is a standard offering for High Pressure Heat Treatment™ (HPHT™) equipment.
ECM USA, Inc.
Dennis Beauchesne General Manager ECM USA, Inc.
Some of the features that are most important are leak rate at deep vacuum along with a chamber and furnace design that does not contribute to any contamination. In our systems, these features, along with others, are of the utmost importance when supplying equipment for the medical implant market.
What are the top 3–5 key requirements or compliance/quality issues needed to heat treat medical implants?
Quintus Technologies
There are several industry standards that have been released to establish key requirements for the HIP process that are often leveraged for medical applications demanding performance and reliability. For example, Nadcap has released AC 7102/6 which details the audit criteria for HIP. This document was developed with significant input from the industry and the government to define operational requirements for quality assurance. It offers a checklist for the HIP processing of metal products and includes requirements for:
managing the equipment per pyrometry standard AMS2750
qualifying technical instructions and personnel training
handling product during the loading and unloading operations
complying with gas purity requirements of the pressure medium
controlling temperature, including uniformity and accuracy evaluations and management
These aspects are critical to ensure product quality meeting medical customer requirements and expectations. Recent additions beyond conventional requirements highlighted above include high speed cooling in the HIP process (>200 K/min) for some materials which is important for metallurgical results.
ECM USA, Inc.
Key requirements include thermal performance (both uniformity and ramp control); real-time vacuum and gas management; traceability and production lot follow up through human machine interface (HMI); quality procedures for all sensor calibrations; and remote access for control and troubleshooting.
Can you share an example of how your equipment could be used to heat treat a medical implant/device from start to finish?
Quintus Technologies
Many medical implants — whether fabricated using conventional processing techniques such as casting, or more novel approaches such as additive manufacturing — require HIP to eliminate process related material defects. Defects include shrinkage porosity for castings and lack-of-fusion and keyhole defects for fusion based additive manufacturing techniques. These defects can have a negative impact on product quality, impacting performance and reliability. Once HIP has been applied to a material, post processing is often not complete, with additional thermal treatments required to achieve the optimum microstructure leading to the desired material properties and performance. Such thermal treatments are material and process dependent, but could include a stress relief, solution anneal, rapid cooling or quenching, and aging and are often applied in separate heat treat equipment.
Hot Isostatic Press QIH 60 offering our most advanced Uniform Rapid Cooling (URC®) furnace technology with industry leading temperature control and accuracy
Quintus Technologies has introduced HIP systems providing capabilities beyond conventional densification. Decades’ worth of work in equipment design, system functionality, and control now offers an opportunity to perform HIP and heat treatment in a combined cycle, referred to as HPHT. Combined HIP and heat treatment for castings and AM implants can mitigate the risk of thermally induced porosity, as well as grain growth, which can offer advantages for mechanical and chemical properties in implants. This methodology provides a more sustainable processing route with improved productivity and energy efficiency. A joint HIP and heat treatment offers significant advantages with lead time, and this improvement in lead time couples well with the demands placed on the personalized medical implants. It also offers opportunities to further optimize microstructures for improvement in material properties coupled with ease of manufacturability. HPHT and modern HIP equipment may allow for a higher performing material system, which produces an implant with improved reliability and life.
Within the medical industry, fine grain AM microstructure, repeatability, and low porosity are key concerns. There are many reported benefits by applying the combined HPHT route such as reduced number of process steps, reduced cycle time and lead time, and improved process and quality control. Other advantages include spending less time at elevated temperatures helping to preserve the fine grain AM microstructure by minimizing grain growth. Tight control and steering of the cooling rates during the different steps of the HPHT cycle ensures repeatability of the properties. Manufacturability can be improved through HPHT as this approach reduces the cooling or quench severity during cooling segments which can often lead to part distortion or cracking. Improved functionality and
control go hand-in-hand with the high quality and reliability demanded in the medical industry.
ECM USA, Inc.
We have several customers making titanium alloy prothesis for various applications: shoulders, hips. Our furnaces are used for post printing processes, such as stress relieving and solution annealing.
Given concerns of metal poisoning, do you know of any changes in alloy composition of medical devices over the last decade?
Quintus Technologies
There are some metals that are becoming more common for implants, including tantalum, magnesium, CP Titanium, etc., and there have been major steps in improving ceramic materials to compete with metals for many applications.
ECM USA, Inc.
As a vacuum furnace equipment supplier, we are not deeply involved in the entire process of material selection. In the early stages of 3D printing joint replacements, from 2013 to 2014, we saw cobalt being part of some alloys. Lately it seems, indeed, that there is a trend in removing that element from the finished parts.
A Happy Ending
Dan McCurdy Former president, Bodycote, Automotive and General Industrial Heat Treatment for North America and Asia
(The rest of Dan's story from the beginning of the article....) The effects of metal poisoning and metal allergies post-surgery can be devastating. In the narrative below, Dan McCurdy shares the story of his wife’s struggle with an allergic reaction to a knee implant, and the heat treating solution that proved to be the best medicine for her.
My wife, an avid runner up and down the hills of Cincinnati, was diagnosed with osteoarthritis in both knees at the age of 53. Her orthopedist suggested a knee replacement for the most degraded one. The replacement was a well-known brand, made from investment-cast ASTM F75 (nominally a Co-Cr-Mo alloy) with full FDA-approval. After a successful surgery and diligent physical therapy, her recovery plateaued, and she experienced chronic inflammation, swelling, and pain.
A blood test, designed to detect allergies to materials used in orthopedic implants, showed a reaction to nickel that was nearly off the charts. We were surprised, as she had previously tested negative for nickel allergies through skin patch testing. The ASTM F75 specification allows for up to 0.5% bulk nickel as a tramp element in implantable devices; however, depending on foundry practices, the concentration of tramp alloys at any point on the surface of a casting can vary significantly. Titanium implants may be the solution to this, but FDA-approved titanium alloys can still contain up to 0.1% Ni.
The solution for my wife, as it turned out, was a different material, originally developed for the nuclear industry, along with an innovative heat treatment process. Created with an alloy of zirconium and niobium (with a maximum nickel content of 0.0035%), her new knee was heat treated at a high temperature in an oxidizing environment, which converts the soft zirconium surface into hard ceramic zirconia, increasing hardness and wear resistance. With this specially heat treated implant in place, my wife is back to nearly 10K steps a day.
References
[1] Magnus Ahlfors and Chad Beamer. “Hot Isostatic Pressing for Orthopedic Implants.” quintustechnologies.com/knowledge-center/hot-isostatic-pressing-for-orthopedic-implants. Quintus Technologies. 2020.
[2] Chad Beamer and Derek Denlinger. “Hot Isostatic Pressing: A Seasoned Player with New Technologies in Heat Treatment — Expert Analysis.” www.heattreattoday.com/processes/hot-isostatic-pressing/hot-isostatic-pressing-technical-content/hot-isostatic-pressing-a-seasoned-player-with-new-technologies-in-heat-treatment-expert-analysis/. Heat Treat Today. 2020.
In this article, explore the importance of alternative advanced manufacturing processes and the effects of post-process heat treating of DMLS titanium alloy parts. In a recent study, a team at Worcester Polytechnic Institute (WPI) evaluated the effects of these processes. Read along to see what they found.
This Technical Tuesday article was first published in Heat Treat Today's December 2022 Medical and Energy print edition.
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Jianyu Liang Professor of Mechanical and Materials Engineering at Worchester Polytechnic Institute Source: WPI
According to Markets and Markets reports, the metal implants and medical alloys market 1 will reach $17.64 billion by 2024, at a CAGR of 9.4%, with titanium metal implants and medical alloys accounting for the largest share of the market. Since it was first reported in the 1940s that titanium had excellent compatibility with human bones, titanium has been used in a wide range of biomedical applications, including arthroplasty and bone replacement, prostheses, craniofacial, maxillofacial, and dental implants, as well as surgical instruments and healthcare goods. 2,3
Although Ti-6Al-4V alloy was originally developed for aerospace applications, its many attractive properties — such as high strength-to-weight ratio, satisfactory biocompatibility, and good corrosion resistance — resulted in it being one of the most widely used biomedical alloys. 4
However, Ti-6Al-4V alloy is very difficult to machine. Traditional Ti-6Al-4V manufacturing processes include casting, wrought (forging/milling from ingots), and powder metallurgy (P/M), with wrought products accounting for 70% of the titanium and titanium alloy market. 5
In recent decades, additive manufacturing (AM) processes have been rigorously
Richard Sisson Key Heat Treat Researcher and Lecturer at Worchester Polytechnic Institute Source: WPI
developed as an alternative advanced manufacturing process for Ti-6Al-4V, especially in personalized biomedical applications. Alternate processes, including powder-bed fusion (PBF), directed energy deposition (DED), and sheet lamination (SL) have been applied in AM processing of titanium and its alloys. 6 Direct metal laser sintering (DMLS), a PBF technology, was the first commercial rapid prototyping method to produce metal parts in a single process and is one of the most widely used AM technologies to manufacture Ti-6Al-4V parts. 7 However, even with the protective oxide film (mainly TiO2), titanium alloys still suffer from pitting and crevice corrosion. Localized breakdown of the protective film leads to the formation of pits. These pits can grow and propagate into macroscopic cracks, which lead to catastrophic failure in orthopedic applications. 8,9
It was reported that post-heat treatment of Ti-6Al-4V parts fabricated by AM techniques could improve its mechanical properties, especially increasing ductility and fatigue strength.
Yangzi Xu Yield & Module Process Engineer at Intel Corporation Source: WPI
However, the changes in corrosion behavior with various post-heat treatments of Ti-6Al- 4V parts fabricated by AM techniques have not been fully understood. In a recent study, a team at Worcester Polytechnic Institute (WPI) evaluated the effects of various post-process heat treatments (including solution treatment and aging, annealing, stress relief, and hot isostatic pressing (HIP)), on the corrosion behavior of Ti-6Al-4V parts manufactured by DMLS. The researchers then proposed a desirable posttreatment procedure that can obtain a good combination of mechanical properties and corrosion behavior of as-printed parts in a simulated body environment. 10,11,12
Ti-6Al-4V dumbbell-shaped tensile testing bars were fabricated by DMLS, according to ASTM standards. The microstructure, phase fraction, porosity, and residual stress of as-printed parts were examined and compared to those of the commercial Grade 5 alloy. It was found that the as-printed samples, mainly composed of acicular α’ martensite phase with a small amount of nano-scaled β precipitates, dispersed in the α’ matrix due to rapid cooling during laser processing, whereas the Grade 5 alloy has an α + β two phase with an equiaxed microstructure. The β phase fractions in the as-printed and Grade 5 alloy were 1.6% and 20%, respectively, based on the results of x-ray diffraction refinement. Furthermore, porosity and defects due to lack of fusion or entrapped gas were observed in the DMLS samples. The rapid cooling rate also resulted in residual tensile stress in the as-printed parts.
The microstructure and phase changes due to different heat-treatment processes were examined and compared to those of the commercial Grade 5 alloy. The corrosion behavior of the heat-treated DMLS parts was studied in simulated body fluid by well-established electrochemical methods.
Microstructure: coarsening of the α lath thickness, more spherical β precipitates. Phase identification: narrowed α characteristic peaks (reduced compressive residual stress) Source: WPI
Transformation from α’ to α phase, coarsening of the α lath microstructure, and the development of β phase were observed in samples after heat treatments. The greatest fraction of β phase was obtained in the high temperature annealed sample. Enhanced corrosion resistance was found in all heat-treated samples. The reasons for improved corrosion resistance after heat treatments include: 1) a passive layer that was developed on the sample surface after heat-treatments; 2) increased β phase fraction and size after heat treatments that led to the reduction of the corrosion susceptible sites. Furthermore, only a single passive layer has been observed in the as-printed sample, whereas double passive layers have been observed in samples after heat treatments at temperature higher than 550°C. However, this second layer, which was largely composed of Al2O3 and V2O5, had very low corrosion resistance compared to that of the primary passive layer that was primarily TiO2.
Microstructure: coarsening of the α lath, and grain boundary can be observed Phase identification: narrowing of α characteristic peaks (reduced microstrain, increased grain size) and evolution of β phase Source: WPI
It was also found that the surface roughness had an exponential effect on the corrosion current density and calculated corrosion rate. A rough surface led to a higher corrosion rate, but a rough surface is known to enhance osteointegration. Therefore, surface roughness needs to be adjusted, based on specific applications.
Microstructure: no significant change in the α lath thickness Phase identification: narrowing of α characteristic peaks (reduced microstrain), evolution of β phase Source: WPI
The effect of porosity was analyzed by using a crevice corrosion test. After a one-month immersion in Ringer’s solution at body temperature, pits were found on the Ti-6Al-4V sample surface near the pores in the as-printed samples, which was due to the formation of localized O2 concentration cells near the pore. Porosity in the as-printed parts was confirmed to impair crevice corrosion resistance. To reduce porosity, HIP was applied at three different temperatures. Based on polarization tests and electrochemical impedance spectroscopy tests, different degrees of reduction in porosity and corrosion-current density were observed in samples after HIP; this reduction was most significant after high-temperature HIP at 799°C (1470°F).
In summary, it was found that high temperature heat-treatment enhanced the corrosion resistance of DMLS Ti-6Al-4V parts. HIP was effective in reducing porosity and improving corrosion resistance. HIP below the annealing temperature (799°C, 1470°F) was recommended as a post-treatment for DMLSprintedTi-6Al-4V, to achieve a good corrosion resistance.
References
[1] “Metal Implants and Medical Alloys Market – Global Forecast to 2024,” 2019. https://www.marketsandmarkets.com/Market- Reports/metal-implant-medical-alloy-market-256117768.html.
[2] R. Bothe, et al., “Reaction of bone to multiple metallic implants.” Surgery, Gynecology and Obstetrics, 1940, 71:598–602.
[3] M. Sarraf, E. Rezvani Ghomi, S. Alipour, et al., “A state-of-the-art review of the fabrication and characteristics of titanium and its alloys for biomedical applications,” Bio-des. Manuf., 2022, 5, 371–395. https://doi.org/10.1007/s42242-021-00170-3.
[4] L.-C. Zhang and L.-Y. Chen, “A Review on Biomedical Titanium Alloys: Recent Progress and Prospect,” Adv. Eng. Mater., 2019, 21: 1801215. https://doi.org/10.1002/adem.201801215.
[5] L. E. Murr, S. A. Quinones, et al., “Microstructure and mechanical behavior of Ti–6Al–4V produced by rapid-layer manufacturing, for biomedical applications,” Journal of the mechanical behavior of biomedical materials, 2009, 2(1), 20-32. https://doi. org/10.1016/j.jmbbm.2008.05.004.
[6] A. Hung Dang Nguyen, A. K. Pramanik, Y. Basak, C. Dong, S. Prakash, S. Debnath, I. S. Shankar, Saurav Dixit Jawahir, and Budhi Dharam, “A critical review on additive manufacturing of Ti-6Al- 4V alloy: microstructure and mechanical properties,” Journal of Materials Research and Technology, 2022, 18: 4641-4661. https://doi.org/10.1016/j.jmrt.2022.04.055.
[7] “Direct Metal Laser Sintering (DMLS) Technology,” Additive News. https://additivenews.com/direct-metal-laser-sintering-dmlstechnology/.
[8] O. Cissé, O. Savadogo, M. Wu, and L’H Yahia, “Effect of surface treatment of NiTi alloy on its corrosion behavior in Hanks’ solution.” Journal of Biomedical Materials Research, 2002, 61/ 3 :
339-345. https://doi.org/10.1002/jbm.10114
[9] Sara A. Atwood, Eli W. Patten, Kevin J. Bozic, Lisa A. Pruitt, and Michael D. Ries,”Corrosion-induced fracture of a double-modular hip prosthesis,” The Journal of Bone & Joint Surgery, 2010, 92/ 6: 1522-1525.
[10] Y. Xu, Y. Lu, K.L. Sundberg, et al., “Eff ect of Annealing Treatments on the Microstructure, Mechanical Properties and Corrosion Behavior of Direct Metal Laser Sintered Ti-6Al-4V,” J. of Material Eng and Perform, 2017, 26: 2572–2582. https://doi.org/10.1007/ s11665-017-2710-y
[11] Ibid.
[12] Z. Yang, Y. Xu, R. D. Sisson, & J. Liang, “Factors Influencing the Corrosion Behavior of Direct Metal Laser Sintered Ti-6Al-4V for Biomedical Applications,” Journal of Materials Engineering and Performance, 2020, 29/6: 3831-3839.
About the Authors
Professor Richard Sisson is a key heat treat researcher and lecturer at Worchester Polytechnic Institute. His main research interest is the application of diffusion and thermodynamics to the solution of materials problems. Currently, he is working on modeling the surface treatment of steels and the postprocessing of AM ceramics and metals. His research endeavors have resulted in over 300 publications and over 300 technical presentations.
Dr. Yangzi Xu is currently working at Intel Corporation as a Yield & Module Process Engineer. She received her PhD at Worcester Polytechnic Institute (WPI) and focuses her research on understanding the mechanical and electrochemical properties of AM Ti alloys with different types of heat treatments, and their corrosion performance in biofluid for potential orthopedic applications. Her background includes research in polymer and food science and engineering.
Professor Jianyu Liang is a Professor of Mechanical and Materials Engineering at Worchester Polytechnic Institute, with affiliated appointments in the departments of Civil and Environmental Engineering, Chemical Engineering, and Fire Protection Engineering. Her research work on nanomaterials, AM, agile manufacturing, machine learning for materials science and manufacturing engineering, and sustainability has been funded by NSF, NASA, DoD, ED, and industry. Her work has resulted in over 300 research papers and technical presentations. As an educator, Liang strives to equip students with the confidence, enthusiasm, knowledge, and skills to allow them to enjoy learning throughout their lives.
For more information
Department of Mechanical and Materials Engineering Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609 Or email jianyul@wpi.edu and sisson@wpi.edu
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