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 and construction, sourcing these large-scale components is an increasingly urgent challenge. This need is felt acutely in the U.S., 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. Their research has the potential to bring large-component manufacturing back to the U.S.
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, or 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.”
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 an 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 percent, 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.
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 they aim to refine.
For more information, contact Greg Cunningham at
