Furnaces North America(FNA) 2024 begins Monday, October 14, and runs through Wednesday, October 16. If you haven’t registered yet, you can still do so onsite, and one look at the technical sessions planned over the two days of training says all you need to know about the caliber of instruction at the event.
All of the sessions will be worth your time! Presenters are highly qualified to speak on the topics, which range from processes and equipment to technology to security:
Emerging Technologies
Furnace Maintenance & Equipment
Heat Treat Business & Digital Transformation
Energy & Gases
Operational Efficiencies
Quality, Compliance & Materials
Process Advancements
If you want to do a little prereading to prepare for the sessions, Heat TreatToday is pleased to direct your attention to technical session presenters who have contributed to our radio, print, and digital resources during this year:
On Tuesday at 8:50 a.m., Bryan Stern, product development manager at Gasbarre Thermal Processing Systems, will be speaking on “The Impact of Oil Quenching – A Look at the Carbon Footprint and Cost of Vacuum vs. Atmosphere Processing.” On June 20, 2024, Bryan was our guest on Heat TreatRadio, episode #110, “Isolated Heat, the Future of Vacuum Furnaces,” which you can listen to here.
Later that morning, at 9:40, Peter Sherwin, global business development manager of Heat Treatmentat Watlow, will focus on “Smart Heat Treatment: Industry 4.0 Innovations for Environmental & Energy Efficiency.” Peter co-authored “Thermal Loop Solutions: A Path to a Sustainable Future in Heat Treatment,” a two-part series published in both the magazine and on our website. You can read the first part here and the second part here.
During that same time slot, Brian Turner, sales application engineer at RoMan Manufacturing, is scheduled to speak on “Efficient Furnace Power Solutions”. Brian joined fellow RoMan employees who have contributed technical content to an ongoing series on controls. You can read that article, “Basic Definitions: Power Pathways in Vacuum Furnaces,” originally published July 16, 2024, here.
On Wednesday at 8 a.m., Sefi Grossman, founder and CEO of CombustionOS, is scheduled to present a session on “Maximizing Heat Treat Operational Efficiency: Digitize Your Data for Automation.” Sefi wrote a piece for our August Automotive print edition on “A New Era: Tracking Quality Digitally,” which was later republished at the website. You can read the digital version here.
At 8:50, Joe Coleman, cybersecurity officer at Bluestreak Compliance, will address “CMMC’s Impending Impact On The Metal Treating Industry.” Just last month, he joined Heat TreatRadio in an interview about “NIST and CMMC: What Heat Treaters Need To Know,” which you can listen to here.
Chad Beamer, senior applications engineer at Quintus Technologies, will speak on “Quintus Purus: Development of Clean HIP Processing” at 9:40 on Wednesday morning. Earlier this year, he collaborated with fellow Quintus employees on an article, “HIP Innovation Maximizes AM Medical Potential,” which you can read here.
Bryan Stern Product Development Manager Gasbarre Thermal Processing SystemsPeter Sherwin Global Business Development Manager Heat TreatmentBrian Turner Sales Applications Engineer RoMan Manufacturing, Inc. Source: RoManSefi Grossman Founder & CEO CombustionOS Source: AuthorJoe Coleman Cyber Security Officer Bluestreak ConsultingChad Beamer Senior Applications Engineer Quintus TechnologiesHeat Treat Today contributors leading technical sessions at FNA 2024
Stop by Heat TreatToday‘s booth (424/426) to let us know how the sessions went and if you did your homework beforehand!
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.
Magnus Ahlfors Applications Engineer – Hot and Cold Isostatic Pressing Quintus Technologies AB
Chad Beamer Applications Engineer – Hot and Cold Isostatic Pressing Quintus Technologies LLC
I’m sure we all know someone, or you may be that someone, who has had a knee or hip replacement. It seems to be commonplace today to have reconstructive joint replacement.
In this Technical Tuesday article by Magnus Ahlfors, Applications Engineer and Chad Beamer, Applications Engineer both in Hot and Cold Isostatic Pressing at Quintus Technologies LLC, explore new developments within hot isostatic pressing (HIP) that can offer opportunities to improve the performance and quality of the implant, while cutting production costs and lead times.
This Original Content article will be released in the upcoming Heat Treat Today Medical and Energy magazine this December 2020. Check here after December 14, 2020 to look at the digital edition.
Introduction
The development of new production technologies over recent years has brought a range of possibilities to manufacturers of orthopaedic
implants for reconstructive joint replacement. Old truths have been challenged, and new ways to increase product performance, quality and cost efficiency introduced. Additive manufacturing (AM) is one of the technologies that have added new flexibility and value in implant manufacturing and is now an important manufacturing method for orthopaedic implants. Perhaps less known is the development within equipment for hot isostatic pressing (HIP) that offers great opportunities to improve the performance and quality of the implant, while cutting production costs and lead times.
Hot Isostatic Pressing of Orthopaedic Implants
Orthopaedic implants are commonly manufactured by casting and additive manufacturing. Metal injection moulding (MIM) is also widely used for dental implants. Implants manufactured by these technologies will contain internal defects such as shrinkage and gas porosity, lack of-fusion between layers and residual porosity after sintering. These internal defects will act as stress concentrations and crack initiation points in the material, which will negatively influence the material properties.
Figure 1. Defect elimination by HIP for E-PBF Ti-6Al-4V [8] (Photo source: Quintus Technologies)Hot isostatic pressing uses a high isostatic gas pressure, up to 207 MPa (30,000 psi), and elevated temperature, up to 3632°F (2000°C), to eliminate these internal defects and achieve a 100% dense material. The elimination of defects results in improved fatigue properties, ductility, and fracture toughness.1-7 For this reason, HIP is widely used for orthopaedic implants like hip, knee, spine, ankle, wrist as well as dental implants to ensure quality and performance and prevent early failure of the implant inside the patient. Common materials are cobalt-chrome alloys like ASTM F75, titanium alloy Ti-6AL-4V, and stainless steel 316L. The densification by HIP for additive manufactured (E-PBF) Ti-6Al-4V is shown in Figure 1 where a printed coupon has been analyzed with X-CT before and after HIP.
New Possibilities with Additive Manufacturing
Developments within additive manufacturing of metal parts have opened up possibilities for patient-specific orthopaedic implants where the implant is tailor-made based on X-ray imaging of the patient for a perfect fit. AM makes patient-specific implants economically viable since there is no tooling such as casting moulds or forging dies; therefore, it is easy to make new unique designs without adding significant cost and lead time to the production process.
Patient-specific implants offer many benefits to the patients and doctors, including better fit to the existing bone structures, shorter surgery times, faster recovery times, and less risk of implant loosening inside the patient.9 The demand for patient-matched implants produced by AM is growing steadily and is predicted to accelerate as production costs are coming down. A fundamental change with personalized implants is that there is no possibility for the healthcare system to stock implants since every implant is unique and made to order. This results in shorter lead times in getting the implant made, which is very important because that is also the wait time for the patient. Minimizing the lead time for the different steps in the manufacturing process, including HIP and heat treatment, is a huge driver.
Optimized HIP and Heat Treatment for AM
The nature of the additive manufacturing process is quite different from conventional casting and forging manufacturing resulting in different microstructures in the as-manufactured condition. For example, the solidification and cooling rates in powder bed fusion (PBF) are several thousand degrees per second, while the casting rate can be a few degrees per minute resulting in microstructural differences even for the same alloy. Despite the differences, most HIP and heat treatment protocols used for AM parts today are developed for cast and wrought material and might not be optimal for AM material. One reason is that these traditional standard HIP protocols are often the only option available in industry today, like at a HIP service provider.
Figure 2. Quintus® QIH48 HIP system (Photo source: Quintus Technologies)
Studies have shown that there is potential to achieve significant improvements in material properties when optimizing the HIP process specifically to AM material. One example is presented in Optimizing HIP and Printing Parameters for EBM Ti-6Al-4V, HIP1710 where an optimized HIP cycle for E-PBF Ti-6Al-4V was investigated as an alternative to the traditional cycle used in industry today of 1688°F, 14.5 ksi (920°C, 100 MPa) and 2 hours soak time. In this study it was found that a modified HIP cycle with lower temperature and higher pressure gave significantly higher yield and tensile strength with retained ductility compared to the traditional HIP cycle. A similar study presented in Evaluation of HIP-Parameter Effects on AM Titanium Ti-6Al-4V 11 shows that that the modified HIP cycle with lower temperature and higher pressure also leads to improved fatigue properties compared to material treated with the traditional HIP cycle for L-PBF Ti-6Al-4V.
A New Era of HIP Equipment
A lot of developments and improvements have been made within equipment for hot isostatic pressing in recent years. A modern HIP system today is space and cost effective and easy to operate and maintain. Quintus Technologies offers HIP systems in a variety of different sizes suitable for a wide range of production volumes. Such product offerings enable the appropriate fit for many business cases.
One important innovation within HIP technology is the rapid cooling capability available in Quintus® HIP systems (Figure 2). The high cooling rates are achieved by a forced convection cooling of the highly pressurized argon gas in the HIP process with a maximum cooling rate up to 7200°F/min (4000°C/min).
Rapid cooling significantly shortens the HIP cycle time since the cooling segment of the cycle takes minutes instead of several hours as compared to a conventional HIP system. This makes the modern HIP system very productive with a lower initial capital expenditure because smaller HIP units can handle higher throughput.
Combining HIP and Heat Treatment
Fast cooling and quenching directly in the HIP system also make it possible to perform many conventional heat treatments for metals, allowing for integrated heat treatment with the HIP cycle.
The main purpose in combining HIP and heat treatment is to eliminate process steps to achieve a shorter and more cost-effective post processing. In Figure 3a, a schematic visualization shows how conventional thermal post processing for a cast, AM or MIM implant, could look when the thermal treatments are performed separately. These steps are often performed in different equipment and sometimes even at different physical sites.
The possibility to do rapid cooling and quenching in the HIP system enables the combination of the HIP and solutionizing step to be performed at the same time in the HIP furnace. Other potential steps such as stress relief, aging, or tempering can also be incorporated into the HIP cycle. In Figure 3b, a potential combined post processing route is shown for the same case as shown in Figure 3a.
When more process steps can be included into the HIP cycle, the total processing and production lead time is reduced. The transfer operations between different steps, for example, from the HIP to a vacuum furnace, are also eliminated saving time and cost. Another benefit is that energy consumption can be reduced by running the combined process, since the parts don’t have to be heated up and cooled down as many times. When combining the HIP and solutionizing step, as seen in Figure 3b, the time at the elevated temperature for the implants can be significantly reduced; that means that potential grain growth during the post processing can be minimized, which is often desired.
HIP and Heat Treatment of CoCr ASTM F75
A good example for combined HIP and heat treatment is cobalt chrome alloy ASTM F75, which is a common material for orthopaedic implants. This material is prone to form carbides during the processing that have a detrimental effect on the mechanical properties.12 The standard HIP cycle for this material is 2192°F, 14.5 ksi (1200°C, 100 MPa) with 4 hours soak time, and at these conditions the carbides will dissolve. However, the carbides will form again during the cool down from the HIP temperature unless the cooling is done fast enough to prevent reprecipitation. The minimum cooling rate required to avoid precipitation of carbides during the cool down is around 360°F/min (200°C/min), according to standard ASTM F3301-18.
Since conventional HIP systems without rapid cooling capabilities will cool much slower than 360°F/min (200°C/min), the material will contain these detrimental carbides after HIP. To correct this, a homogenization or solution anneal treatment is added after the HIP step. Treatment parameters typically consist of a soak at 2192-2246°F (1200-1230°C) for 4 hours in a vacuum furnace where the minimum cooling rate can be achieved. Therefore, the parts are moved to a different type of furnace and heated up to the same temperature and soak time as the HIP process with the sole purpose to achieve a high enough cooling rate to obtain the desired microstructure and properties.
Thanks to the rapid cooling in a modern Quintus® HIP system, ASTM F75 components instead can be cooled directly in the HIP system at a high enough rate to avoid carbide formation and thereby completely eliminating the need for a separate homogenization/solution treatment. The result is that only one thermal treatment is needed instead of two, one piece of equipment needed instead of two, and the material will spend 4 hours at elevated temperature instead of 8 hours, which is beneficial. This is applicable on both cast and AM implants as well as MIM.
Figure 4. Size of femoral knee implant used for case study (Photo source: Quintus Technologies)
The Productivity of a Modern HIP System
The rapid cooling capability of these systems lead to a significant reduction in the HIP cycle time and thus, improved productivity of the production chain. To demonstrate the high capacity of these HIP systems, a production case is presented below where two Quintus® HIP systems, the QIH15L and the QIH48, have been compared.
For this case study, a femoral knee implant made of ASTM F75 has been chosen. The size of the implant can be seen in Figure 4 represented by a cylinder. It is assumed that the implants are not allowed to be in contact with each other during the HIP cycle, so it calculates how many cylinders can fit in each furnace, making the calculation conservative. The HIP parameters for this case are 2192°F, 14.5 ksi (1200°C, 100 MPa) and 4 hours with rapid cooling, which will determine the HIP cycle time. The production conditions in this case are chosen to be 24 hours/day, 5 days/week and 48 weeks/year with a 90% uptime of the HIP system. All input data is summarized in Table 1 and the results are presented in Table 2.
As can be seen in Table 2, the QIH15L can process 58,300 implants per year while the QIH48 can produce 611,200 in the same time frame. These numbers are quite high considering these two HIP models belong to the Quintus® Compact HIP series and are relatively small units aimed at in-house production lines. The HIP cycle time is around 8 hours and the larger HIP system, the QIH48, has a slightly longer cycle time compared with the smaller QIH15L. This cycle time is calculated with the assumption that rapid cooling is used. If a conventional system without rapid cooling is used instead, the total HIP cycle time can be as much as twice as long, close to 16 hours total, showing the impact of the rapid cooling capability on system productivity. Of course, this would be reflected in half the number of parts per year. A more comprehensive productivity and cost analysis for modern HIP systems have been made in Cost-Effective Hot Isostatic Pressing – A Cost Calculation for MIM Parts.13
The Benefits of Insourcing the HIP Process
Traditionally, most orthopaedic implant manufacturers have been outsourcing the HIP process to external HIP service providers rather than having the HIP process in-house, and that is still the situation today. A benefit of using a HIP service provider is that it is a cost-effective alternative even for relatively small annual volumes. This is possible since the service provider can consolidate different lots from different customers together in one HIP cycle, so called coach cycle, making it a cost-effective route.
However, insourcing the HIP process is becoming more interesting and some implant manufacturers have already invested in HIP equipment to facilitate the HIP process in-house. One reason for this trend is the strong technical development of the modern-day HIP equipment, as already discussed in the previous chapter.
Insourcing the HIP process has several positive aspects and some are discussed here below:
Shorter production times – Since the time of transport to and from the service provider is eliminated along with the turnaround time at the service provider, the lead time for HIPing the implants can be significantly reduced. When HIP with in-HIP heat treatment capability is fully integrated into the production process, process steps can be eliminated and time waste can be minimized.
Eliminate risks – Since the transporting to and from a service provider is eliminated, so are the risks related to transport delays and damaged/lost goods.
Production flexibility – Full control over the production schedule and lead times result from the flexibility to run cycles when needed and possibly to fast-track time-critical deliveries through the internal schedule. This can be important for patient-specific devices where short lead time is always a requirement.
Control over quality and process improvement – With the full HIP and heat treatment process in-house, the quality system can be further developed to avoid mistakes and non-conformities, while good-receipt inspection can be minimized. Typical issues can include loss of implant traceability, parts being treated with the wrong HIP parameters, and surface contamination such as surface oxidation and alpha casing etc. Internal know-how and expertise on how to run the HIP process will be developed over time to avoid quality issues and delays, all with the help of the Quintus Care® program.
Optimized HIP and HT protocols – When operating the HIP process in-house, one is not limited to the standard coach cycle generally offered by the HIP service industry. Instead, the HIP process can be tailored for the needs and requirements of specific parts and materials made by casting, AM, or MIM to achieve maximum performance and quality of the implants. This possibility is extra important for parts produced by additive manufacturing (AM) since optimized HIP cycles, specifically for AM material, can result in significantly improved material properties compared to the standard HIP cycles as has been shown. Opportunities include integrating different heat treatments into the HIP cycle that are enabled by rapid and steered cooling to achieve the most effective production route, facilitating in-house R&D to continuously improve HIP processing, and optimizing for new products and applications. Today, there are HIP service providers on the market who have modern HIP systems with rapid cooling capabilities that can also offer optimized cycles and combined HIP and heat treatment.
Lower total production cost – Having a high utilization rate on an in-house HIP system yields the lowest operating cost for the HIP process. The cost for heat treatment can potentially be eliminated completely if the combined HIP and heat treatment approach can be used. Since transportation to external sub-contractors can be avoided, the cost of transportation is eliminated as well as the cost of insurance during transport. There are also potential indirect cost savings from improved quality control routines, more flexible planning, and shorter delivery times.
So, overall control of the process when operating in-house is one of the key benefits when coupled with better properties of the implants, short lead times and low cost for the process.
Conclusions
In this paper we have discussed the development of modern HIP technology such as the possibility to perform rapid and steered cooling directly in the HIP, which gives a significantly improved production capacity of the HIP system. The rapid cooling capability of modern Quintus® HIP systems also makes it possible to include heat treatment processes directly into the HIP cycle with the purpose of eliminating process steps for shorter lead times and more lean production.
AM is growing as a production method for orthopaedic implants with a potential for modifying and optimizing the HIP cycles for AM-produced components. Such optimized approaches offer a product with enhanced material properties compared to traditional HIP cycles, which were often developed for cast and wrought material.
The advantages of operating the HIP process in-house include minimal lead time, control over quality, process improvement, flexibility in production planning, the possibility to use optimized HIP cycles, and a lower total production cost from direct and indirect cost savings.
References
[1] JJ. Lewandowski and M. Seifi, Metal Additive Manufacturing: A Review of Mechanical Properties, Annual Review of Materials Research 46, pp. 151-186, 2016.
[2] J. Kunz et al., Influence of HIP Post-Treatment on the Fatigue Strength of 316L-Steel Produced by Selective Laser Melting (SLM), Proceedings WorldPM2016, Oct. 2016, Hamburg, Germany.
[3] S. Leuders et al., On the Fatigue Properties of Metals Manufactured by Selective Laser Melting: The Role of Ductility, J. Mater. Res. 29, 1911–1919, 2014.
[4] N. Hrabe et al., Fatigue Properties of a Titanium Alloy (Ti–6Al–4V) Fabricated Via Electron Beam Melting (EBM): Effects of Internal Defects and Residual Stress, International Journal of Fatigue vol. 94, pp. 202–210, Jan. 2017.
[5] J. Haan et al., Effect of Subsequent Hot Isostatic Pressing on Mechanical Properties of ASTM F75 Alloy Produced by Selective Laser Melting, Powder Metallurgy vol. 58 no. 3, pp. 161–165, 2015.
[6] V. Popov et al., Effect of Hot Isostatic Pressure Treatment on the Electron-Beam Melted Ti-6Al-4V Specimens, Procedia Manufacturing, vol. 21, pp. 125-132, 2018.
[7] R. Kaiser et al., Effects of Hot Isostatic Pressing and Heat Treatment on Cast Cobalt Alloy, Materials Science and Technology, Vol. 31, No. 11, Sept. 2015.
[8] S. Tammas-Williams et al., The Effectiveness of Hot Isostatic Pressing for Closing Porosity in Titanium Parts Manufactured by Selective Electron Beam Melting, Metall. Trans., Volume 47, Issue 5, pp 1939–1946, May 2016.
[10] M. Ahlfors et al., Optimizing HIP and Printing Parameters for EBM Ti-6Al-4V, HIP17 – 12th International Conference on Hot Isostatic Pressing, Dec. 2017, Sydney, Australia.
[11] T. Kosonen and K. Kakko, Evaluation of HIP-parameter Effects on AM Titanium Ti-6Al-4V, AeroMat19, May 2019, Reno, Nevada.
[12] M. Chauhan, Microstructural Characterization of Cobalt Chromium (ASTM F75) Cubes Produced by EBM Technique, Master Thesis at Chalmers University of Technology, 2017.
[13] M. Ahlfors et al, Cost-Effective Hot Isostatic Pressing – A Cost Calculation for MIM Parts, Metal Injection Molding International, Vol 12 No. 2, June 2018.
About the Authors:
Magnus Ahlfors works as application engineer in hot isostatic pressing where he is heavily involved in the development and optimization of HIP processes for different industries, especially for metal additive manufacturing. Magnus has a MSc in Materials Engineering from Chalmers University of Technology, Sweden and has worked at Quintus Technologies since 2013.
Chad Beamer has a MS from the Ohio State University in Material Science and has worked as a material application engineer with GE Aviation years and as a technical services manager with Bodycote. In February, Chad began working with Quintus Technologies as an applications engineer for the Advanced Material Densification division focusing on hot isostatic pressing (HIP). 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.
Hot isostatic pressing (HIP) has been a player in heat treating for 50 years, but recent advances in its technology are providing cutting edge opportunities for new applications in the thermal processing industry.
Heat Treat Today asked two experts in the HIPing world about the state of hot isostatic pressing: What are the latest technologies and where are its potential growth markets in the thermal processing industry? They represent both sides of HIPing – one from a HIP equipment manufacturer and the other from a HIP process/service provider. Each gives a unique perspective on the HIP market and the industry itself.
Our expert contributors are Chad Beamer, an applications engineer in Hot Isostatic Pressing, at QuintusTechnologies, a high pressure technology company, and Derek Denlinger, a corporate lead metallurgist at Paulo, a thermal processes and metal finishing operations company. This Original Content Technical Tuesday article was taken from 2020 Q4 Heat Treat Todayprint magazine.
What is HIP?
Derek Denlinger Corporate Lead Metallurgist Paulo
Paulo’s Derek Denlinger says, “Hot isostatic pressing is fundamentally, when parts simultaneously see high temperature (in some cases as much as 2500oF) and very high pressure (up to 30,000psi) from all directions for a duration of time.”
Chad Beamer Applications Engineer – Hot and Cold Isostatic Pressing Quintus Technologies LLC
Chad Beamer of Quintus adds, “Pressure-based compaction processes can be used to establish density by applying a uniaxial pressure within rigid dies. Such mechanical or hydraulic approaches can produce non-complex parts or ‘green’ compacts. Although a cost-effective and high-throughput technique, these conventional presses exhibit geometrical limitations and compressibility constraints, yielding product that is not uniform in density and microstructure.”
“Isostatic pressing was developed with the desire to improve upon these shortcomings,” continues Beamer. “Such compaction techniques leverage Pascal’s law by using a fluid contained in a pressure vessel, either in the liquid or gas state, to transmit equal pressure in all directions on the surface of a workpiece.”
Beamer further explains, “Various isostatic pressing techniques exist today such as cold isostatic pressing (CIP), warm isostatic pressing (WIP), and hot isostatic pressing (HIP). HIP is a heat treatment process that utilizes isostatic pressure via a gas at high temperatures. It is commonly used to consolidate metal or ceramic powder and to reduce defects present in castings and additively manufactured parts. The output is a product with improved mechanical properties, workability, and reliability.”
Pore eliminated before and after HIP process
What happens in the HIPing process?
Denlinger explains, “In the HIPing process, parts are heated to a temperature high enough to weaken material strength. High pressure, usually applied through a pressurized gas medium such as argon, applies a compressive stress onto the part from every direction. Given a hold period of time, this compression effectively allows for internal voids or pores to close up due to a mixture of mechanical deformation, creep, and metallic diffusion. The part consolidation sets the stage for any other heat treatment that may follow in order to maximize material performance.”
Since the densification of the workpiece is achieved by the simultaneous application of pressure and elevated temperature during HIP, Beamer adds, “Temperatures are usually in the range of 900oF-3600oF (500o-2000oC) depending on the material being HIPed. A good rule of thumb is a temperature targeting approximately 80% of the materials solidus temperature. Pressures in the vessel can reach twice that of the pressure at the bottom of the Mariana Trench, generally in the range of 15,000-30,000 psi (100-200MPa). The combined temperature and pressure applied should be capable of exceeding the yield strength of the material.”
Latest HIP Technologies
Both Beamer and Denlinger share optimism about the new HIP advancements, especially the new high pressure heat treatment (HPHT).
Beamer states, “A recent development in HIP technology is the ability to perform rapid gas cooling and quenching in the HIP system. Originally developed to shorten cycle time, this advancement is now being leveraged to perform many of the standard heat treatments for metals in the HIP furnace. Now a single piece of equipment can be used to apply both HIP and heat treatment, all carried out in one cycle. This approach is referred to as high pressure heat treatment (HPHT). Benefits to this new treatment include:
the ability to remove an additional process step and piece(s) of equipment
more cost-effective manufacturing path
fewer times a component must be heated up
less time spent at elevated temperature
elimination of the risk of thermally induced porosity (blistering) in additively manufactured parts
“These modern systems are continuing to evolve with other promising advancements such as steered cooling. This controlled cooling approach within a HIP vessel allows cooling rates for a component to be optimized in order to achieve the desired microstructure. These advancements are quite exciting for many industries as they are expanding the design windows for material systems and creating new opportunities within a HIP system.”
“HIP has been around commercially for around 50 years,” Denlinger points out, “but more recent technology has been focused on better control of thermal aspects of the process. This is opening the doors for more fine-tuned ‘high pressure heat treatment’ processing that can offer speed and, in some cases, performance benefits that were previously not possible. These types of processes have often been coupled with the ever-growing additive manufacturing processes, though applications to more traditional manufacturing methods are gaining momentum. The influence of pressure on diffusion and transformation in materials has been identified, but not fully explored for many alloys, so new high pressure heat treatments are now being considered to compete with traditional HIP and heat treatment methods.”
What is HIP’s niche in the thermal processing industry? Who are its customers? Where do you see potential growth markets?
HIP implants
According to both men, the future is bright for HIPing.
Beamer explains why specific industries choose HIPing: “HIP is often desired where the risk of failure is not an option. Therefore, it is not surprising that HIP is commonplace in aerospace, energy, and medical industries. Applications within these industries include densification of products, consolidation of powder, diffusion bonding, as well as HPHT. For the aerospace industry, HIP is used to remove porosity from nickel-base and titanium-base castings as well as defects present in additively manufactured parts. The medical industry applies HIP to improve the quality and durability for cobalt chrome and titanium implants. HIPing of large and complex near-net-shape powder metal components to achieve fully densification is routine in the energy industry.”
Denlinger agrees, “HIP has most often been used for fatigue benefits, which is an important performance criterion in the aerospace industry. This remains in the scope, but applications in other sectors are growing due to the adoption of additive manufacturing. Oil and gas, medical, manufacturing equipment, space, firearms, and other industries are increasing their use of HIP and high-pressure heat treatment. Partnering with companies to explore additive manufacturing solutions with both HIP and traditional heat treatment in our arsenal has been very successful; challenging the status quo with the latest HIP technology and our expertise in heat treatment has been a great learning experience.
Regarding market expansion for HIP, Beamer shares, “Potential growth markets for HIP include medical, defense, space, automotive and the ongoing developments with additively manufactured applications. The medical industry is showing growth with an aging population coupled with a cultural shift to living a more active lifestyle. Another trend within the medical industry is to insource HIP versus going through a supplier, which can offer process optimization opportunities and increased quality control.”
The future of HIP technology is likely to include the automotive industry.
Beamer continues, “Growth for HIP in the defense industry can be attributed to strong government funding, such as the development work being done through America Makes. One of the most exciting growth markets here in the US is space, in which many high-profile companies are showing interest in HIP and HPHT technologies.
“Although the HIP process is not typically characterized as a high-volume process,” Beamer concludes, “the automotive industry is finding its benefits useful for cast engine blocks and emerging technology such as binder jet applications. Despite the present challenges due to the Covid-19 pandemic, specifically within the civil aerospace industry, there are many exciting growth opportunities for HIP.”
(All photos in this article provided by Quintus Technologies)
About the Authors:
Chad Beamer has a MS from the Ohio State University in Material Science and has worked as a material application engineer with GE Aviation for 7 years and as a technical services manager with Bodycote for 5 years. In February, Chad began working with Quintus Technologies as an application engineer for the Advanced Material Densification division focusing on hot isostatic pressing (HIP). 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.
Derek Denlinger is the corporate lead metallurgist at Paulo. Derek has a Bachelor of Science in Metallurgical Engineering from Missouri S&T in Rolla. He started in the foundry industry before transitioning to heat treatment at Paulo where he has been for the past 5 years. The past two years, Derek has been focused on additive manufacturing and hot isostatic pressing assisting with Paulo’s entry into the HIP market.
