An optical laboratory in northeastern USA will receive a second floor-standing box furnace for heat-treating ceramics and optics used in the medical field.
The L&L Special Furnace Company model XLE 3636 has an effective work zone of 34” wide by 30” high by 32” deep. It features a double pivot horizontal door. The ceramic hearth is supported on lightweight castable piers. A series of heat shields are included to ensure a safe case temperature while at operating temperatures. The furnace is designed for use with inert blanketing gas for atmosphere control to minimize oxidization. A manual flow panel with regulator and flow meter is included.
A Eurotherm program control and high limit safety are standard. The furnace has a stack light mounted to the top of the control panel for an audible and visual indication of current furnace status. Solid-state relays drive the furnace, which is NFPA86 compliant. Startup and training packages are also included to help the customer set up the furnace and process.
Greg Stapcup CEO/President SITES Medical Source: SITES Medical website
SITES Medical has ordered two vacuum furnaces, expanding their heat treat capabilities. SITES Medical is an orthopedic technology development company that invents and de-risks new technologies, and the furnaces will aid them as they collaborate with OEMs to bring technologies to market and drive mutual growth.
The new furnaces from Ipsen will accommodate increased volume resulting from growth in business. Each has a work zone size of 24” wide x 24” high x 36” deep with an all-metal hot zone. The furnaces will be used for orthopedic implant processing such as stress relieving Ti and CoCr components, as well as diffusion bonding of Ti and CoCr implants.
"After reviewing the options available for thermal processing solutions," said Greg Stalcup, president/CEO of SITES Medical, "we elected to purchase the Ipsen TurboTreater® vacuum furnaces due to their high quality and reliability."
A North American heat treat supplier will be sending a vacuum furnace to a power tool manufacturer in the U.S. and a medical implant manufacturer.
The supplier, Ipsen’s Vacuum Technology Excellence Center, was awarded these two furnace orders at the beginning of 2021. The power tool manufacturer will receive an Ipsen TurboTreater® as part of a plan to increase production capacity. It will be the ninth vacuum furnace at that location from the U.S. supplier .
The medical implant manufacturer, looking to expand production capacity, chose Ipsen’s MetalMaster® external quench vacuum furnace. The furnace will be designed with an all-metal hot zone for long, high temperature cycles. Its multi-staged pumping system is capable of providing low residual oxygen levels for processing titanium components.
Solar Manufacturing Mentor® Furnace Source: Solar Manufacturing
A medical device and implant manufacturer in the Southeast USA recently received a vacuum furnace. The furnace will be used to age harden and anneal medical devices and implants.
The Model HFL-2018-2IQ Mentor® vacuum furnace by Solar Manufacturing features an all-metal insulated hot zone, a load weight capacity of up to 250 lbs., and a maximum operating temperature of 2400° F.
Dan Insogna Southeast Regional Sales Manager Solar Manufacturing (photo source: solarmfg.com)
“We were awarded the project based on our relationship with Solar Atmospheres and our quick furnace delivery,” states Dan Insogna, southeast regional sales manager at Solar Manufacturing. “Together, we delivered the Mentor® furnace along with a water system, and a custom heat treat recipe for the medical grade components being processed. Our customer was up and running with their new… furnace within a week of delivery.”
(Photo Source: BruceBlaus – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=44967235)
Michel Frison VP Global Sales Nitrex and G-M Enterprises (Source: Nitrex.com)
A medical device manufacturer has acquired a vacuum furnace that will bring heat treating in-house, reducing lead time and improving process control. The application is for the heat-treatment of steel dies used in the company’s plastic and metal injection molding operations.
The vacuum furnace is the first purchase from G-M Enterprises, a Nitrex company. G-M Enterprises completed the installation at the company’s newly expanded greenfield facility. The turnkey solution features a horizontal front loading vacuum furnace G-M model HVF 101-(I)XB with 6-Bar internal quench capabilities and a work area of 18” x 18” x 24” (457 x 457 x 610 mm), with an all-metal furnace construction. The system is part of the company’s metal injection molding operations.
Vacuum Furnace Source: Nitrex
"We are proud of continually maintaining G-M Enterprises’ long-standing relationship with the medical industry," said Michel Frison, VP Global Sales, Nitrex and G-M Enterprises, "providing solutions that aid in improving the affordability and accessibility of high-quality healthcare."
Medical devices, medical tools, and prosthetics all have a long history with heat treating. As we look to the future, the materials industry and the advancement of AM into the heat treat industry is moving at lightning speed.
In this article by Trevor Jones, CEO, Solar Manufacturing Inc., see why vacuum furnaces are excellent choices for accurately providing the necessary process parameters for this incredible medical technology that can provide people with mobility, function and independence to improve their quality of life.
This original content column was originally published in Heat Treat Today's Medical and Energy magazine, December 2020.
Trevor Jones CEO Solar Manufacturing, Inc. Source: Solar Manufacturing, Inc.
Thermal processing of metallic alloys is the backbone of the heat treating industry. Speaking of backbones, the human spine, a critical part of the human body, can now be replaced with an additively manufactured and heat treated prosthetic metallic alloy spine. Medical devices, medical tools, and prosthetics all have a long history with heat treatment. As we look to the future, the materials industry and the advancement of AM into the heat treat industry is moving at lightning speed.
AM parts require precise heat treating especially, when it comes to atmosphere control, temperature uniformity, and flexibility. Vacuum furnaces are ideal for accurately providing each of these process parameters. Let’s take a look at each of these heating treat parameters a little more closely.
Atmosphere Control
Vacuum, by nature, is a neutral atmosphere which, in part, means it has no carburizing or decarburizing potential. Therefore, the surface of the parts that is directly exposed to the vacuum atmosphere cannot gain or lose the base carbon content of the alloy. Additionally, vacuum is practically void of oxygen. If the parts were exposed to oxygen at the elevated processing temperatures, the surface of the parts would become oxidized. In minor cases, a superficial oxidation layer would be the result. In more severe cases, the surface could experience alloy depletion and diffused oxygen.
This is particularly important when processing titanium alloys, which are inherently more sensitive to carbon, oxygen, and nitrogen. When titanium is exposed to any of these elements, a metallurgical phase called “alpha case” can develop on the surface of the titanium and diffuse inwards towards the core of the part.
In most applications, the alpha case is undesirable, and precautions should be taken to prevent it.
Vacuum processing can also provide an atmosphere where an elemental substance, like nitrogen, can be kept in balance with the parts being processed. For example, if an AM part intentionally contains nitrogen, processing this part in a deep vacuum may remove some of the nitrogen base content in the part. To prevent this from occurring, partial pressure nitrogen in the vacuum furnace keeps the nitrogen in equilibrium. The surface condition of these parts is extremely important especially if the AM parts will be implanted into the human body.
The medical processing room at Solar Atmospheres. Source: Solar Manufacturing, Inc.
Temperature Control
The working zone of the furnace encompasses the parts being processed. It is critical that this entire working zone volume be thermally uniform to achieve predictable and consistent results. If any area of a working zone is cooler or hotter than the temperature of another area, it may negatively impact the heat treatment results including difference in mechanical properties and dimensional changes of the parts. For example, if the process is stress relieving and the parts were not subjected to high enough temperature for the requisite time, the parts may still contain some residual stresses.
Residual stresses can have various negative consequences during manufacturing, including cracking and part distortion – during build and finish machining. Tensile residual stresses in finished parts can also reduce fatigue and corrosion performance.1 A failure of a medical implant in the human body would be disastrous if it could have been avoided with proper heat treating!
Medical Instruments Source: ??
With proper design, vacuum furnaces can provide very tight temperature uniformity of ±5°F with direct part temperature monitoring throughout an entire working zone over a broad temperature range.
Flexibility
The vacuum furnace is extremely versatile in the infinite amount of process variables that are available to be adjusted, including heating rates, soaking temperatures, soaking times, atmospheric conditions, and cooling rates. All these variables can be adjusted to provide precisely what is required for a given alloy to optimize the heat treatment needs for the part being processed. To meet the need of the modulus and the strength and fatigue characteristics of a medical implant, AM technology can adjust the mechanical properties of the implant by changing some of the parameters in the processing.2
One of the many steps in the AM process is heat treating, and vacuum furnaces provide the flexibility that can be tailored to the alloy and heat treatment required. Having an AM prosthetic custom vacuum heat treated to fit the human body, could be the key to its success.
Vacuum furnaces and their unique heat treatment processes are ideal for providing the atmosphere control, temperature control, and flexibility that are essential for AM medical devices, tools, and prosthetics. As the AM market expands and the technology advances, vacuum furnace technology will continue to be integral in fostering that growth.
About the Author:
Trevor Jones began his career as the project engineer at Solar Atmospheres commercial heat treating on their Research and Development Team, concentrating on the improvement of vacuum thermal processing equipment and the development of new processes. He is currently the CEO of the Solar Manufacturing, Inc., a division of the Solar Atmospheres Family of Companies.
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.
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