Researchers at the Department of Energy's Oak Ridge National Laboratory are using advanced manufacturing techniques to revitalize the domestic production of very large metal parts that weigh at least 10,000 pounds each and are necessary for a variety of industries, including clean energy.
Across sectors spanning aerospace, defense, nuclear, oil, gas, renewables, construction and more, sourcing these large-scale components is an increasingly urgent challenge. This need is felt acutely in the US, where traditional manufacturing techniques like casting and forging have declined and moved overseas-resulting in supply-chain shortages.
Today, ORNL researchers are advancing an increasingly viable alternative to casting and forging known as powder metallurgy-hot isostatic pressing, or PM-HIP for short. Their research has the potential to bring large-component manufacturing back to the US.
Senior research scientists Jason Mayeur and Soumya Nag are innovating to push PM-HIP far beyond its decades-old origins with the addition of process improvements-including the use of 3D-printing methods like wire-arc additive manufacturing (WAAM) and hybrid (additive and subtractive) manufacturing, as well as in-situ monitoring and advanced computational modeling. These techniques can create PM-HIP molds faster and more accurately. In turn, PM-HIP is made not only more precise and effective, but also more affordable, and more viable for American manufacturing.
"PM-HIP is a vital pathway for diversifying the supply chain for producing large-scale metal parts that are becoming more difficult to source via conventional means," Mayeur said. "The technology is of particular interest to the nuclear and hydroelectric industrial sectors, as well as the Department of Defense."
New approach revitalizes an existing manufacturing technique
In contrast with traditional casting and forging techniques, the PM-HIP manufacturing process involves fabricating pre-formed, hollow molds for each large-scale component and filling them with metal powder. Once the 3D-printed mold, also known as a "can" or "capsule," receives an initial seal, any gas remaining inside is pumped out. Then, a more permanent, hermetic seal is applied.
At this point, the capsule is heated and pressurized in prescribed cycles within a hot isostatic press, or what is essentially a pressurized furnace. Without melting, these cycles facilitate the consolidation of the metal powder into the required shape, in a process exchange of heat and pressure known as solid-state bonding. When bonding is complete, acid leaching or machining is used to remove the exterior can, revealing the intended part.
Mayeur works in the Deposition Science and Technology Group at ORNL, where he applies his expertise in computational solid mechanics to manufacturing challenges. His two-decade research career began with the use of computational models to understand the relationships between materials microstructure and performance. He has since segued into the analysis of the structural material performance of metals and alloys.
In this arena, Mayeur develops theory, writes code to implement his theories and then performs simulations of solids under various loading conditions to determine their suitability for use in a variety of applications. In short, Mayeur's code improves the PM-HIP process, helping to make it a more attractive alternative to traditional casting and forging.
Nag, Mayeur's colleague at ORNL, works in the Materials Science and Technology Division, applying his own two decades of research experience in materials and manufacturing. As a metallurgist with expertise in evaluating lightweight, high-temperature structural alloys fabricated via conventional and advanced manufacturing techniques, Nag's work effectively complements Mayeur's.
"Jason is an expert in predictive modeling of deformation characteristics of hot isostatic pressing cannisters. I am more involved on the experimental side of things. Jason and I complement each other, and really, our two efforts are very much intertwined and critical toward the overall success of the task," Nag said.
Nag's research centers on the processing and materials science of HIP capsule fabrication, using various additive manufacturing techniques and assessing the resulting component part quality. "Additive manufacturing offers unique design flexibility, which, combined with the reliability of PM-HIP, can pave the path toward precise manufacturing of large-scale, custom and complex, energy-related parts, while also taking advantage of multi-material builds," he said.
Nag collaborates with Mayeur to design and perform experiments that characterize the metal powder material's behavior and its mechanical properties in pursuit of a better, more accurate build, while providing the necessary material property inputs for Mayeur's computational models.
Mayeur's work targets many technological challenges posed by the PM-HIP process, striving for quality and consistency in geometry to achieve dimensional accuracy at a very large scale. One challenge is shrinkage. During PM-HIP, the volume of metal powder within the can shrinks by approximately 30%, but this shrinkage is far from uniform.
To address these inconsistencies, Mayeur's computational models can "predict how this shrinkage occurs for different part geometries and capsule designs. This is an iterative process that occurs between the initial capsule design and the final design, using the simulation results as a guide to modify it.
Research attracts attention at conferences
Mayeur recently presented his work at the World Congress on Computational Mechanics (WCCM) in Vancouver, British Columbia. His broader interest in computational mechanics and experience with microstructure-related models and research problems led him to develop a curiosity about problem solving for PM-HIP.
"I saw an opportunity to make an impact by helping to enable the broader adoption of this technology that has the potential to help address these critical supply chain issues impacting both energy and national security," he said.
Nag recently presented his own research at the 2024 AM/PM conference in Pittsburgh. "This was one of the first attempts to utilize convergent manufacturing techniques, coupling additive manufacturing and PM-HIP, to fabricate surrogate parts toward manufacture of pressure boundary reactor vessels," Nag said. He has also been asked to present his additional research and findings at the forthcoming International Conference on Advanced Manufacturing (ICAM) in Atlanta, Georgia.
Together, Mayeur and Nag contribute to a team with expertise in manufacturing, materials modeling and monitoring, to perform revealing research on PM-HIP component part production. Combining their backgrounds in experimentation and computation, they share an innovative approach comprised of both materials science and mechanical behavior for the task at hand.
Mayeur and Nag share a goal of innovating to make massive metallurgical manufacturing a more precise and viable option for large-scale components. Both ORNL researchers are excited to fuel ongoing improvements to the broader viability of PM-HIP, an established, yet in-flux technology that their individual and collective work continues to refine.
On October 9-10, 2024, ORNL-along with the Metal Powder Industries Federation and the Electric Power Research Institute-is hosting a PM-HIP Workshop at ORNL's own Manufacturing Demonstration Facility. The goal of this workshop is identifying the key challenges currently inhibiting the broader adoption of the approach, Mayeur said.
The MDF, supported by AMMTO, is a nationwide consortium of collaborators working with ORNL to innovate, inspire and catalyze the transformation of U.S. manufacturing.
"ORNL's role would be to start tackling, in conjunction with industry and other partners, the research required to enable this technology to grow," Mayeur said. "DOE's Advanced Materials and Manufacturing Technologies Office is very interested in promoting this effort and is becoming increasingly more involved in the workshop planning and the technology in general."
Registration for the PM-HIP Workshop at ORNL is open through September 5, 2024.
The research was funded by AMMTO and the Advanced Materials and Manufacturing Technologies (AMMT) program, sponsored by DOE's Office of Nuclear Energy. The Office of Nuclear Energy is focused on accelerating the development, qualification, demonstration and deployment of advanced materials and manufacturing technologies to enable reliable and economical nuclear energy.
UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit https://energy.gov/science.
