ORNL research aims to support production of large-scale components
November 13, 2024
Researchers from the US Department of Energy’s Oak Ridge National Laboratory (ORNL), Tennessee, USA, are turning to advanced manufacturing, including Hot Isostatic Pressing (HIP) Powder Metallurgy and Additive Manufacturing, for the production of parts weighing upwards of 4,500 kg.
Across sectors spanning aerospace, defense, nuclear, oil, gas, renewables and construction, sourcing these large-scale components is an increasingly urgent challenge, states ORNL. This need is felt acutely in the US, where traditional manufacturing techniques like casting and forging have declined and moved overseas and resulted in supply-chain shortages.
Senior research scientists Jason Mayeur and Soumya Nag are hoping to add Wire Arc Additive Manufacturing (WAAM), hybrid manufacturing, in-situ monitoring and advanced computational modelling to HIP technology to create moulds faster and more accurately, whilst leveraging the PM technology American manufacturers may be more acquainted with.
“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 explained. “The technology is of particular interest to the nuclear and hydroelectric industrial sectors, as well as the Department of Defense.”
New approach aims to revitalise existing manufacturing technique
In contrast with traditional casting and forging techniques, PM-HIP involves fabricating pre-formed, hollow moulds for each large-scale component and filling them with metal powder. Once the additively manufactured mould (aka 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 pressurised in prescribed cycles within a Hot Isostatic Press (essentially a pressurised 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.
Jason Mayeur works in the Deposition Science and Technology Group at ORNL, where he applies his knowledge 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 can be used to improve the PM-HIP process, thus making it a more attractive alternative to traditional casting and forging.
Soumya 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. Nag is a metallurgist with expertise in evaluating lightweight, high-temperature structural alloys fabricated via conventional and advanced manufacturing techniques.
“Jason is an expert in predictive modelling of deformation characteristics of Hot Isostatic Pressing canisters. 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 centres 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 explained.
Nag collaborates with Mayeur to design and perform experiments that characterise the metal powder material’s behaviour 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 not uniformly.
To address these inconsistencies, Mayeur’s computational models work to predict how the shrinkage occurs for different part geometries and capsule designs. This is an iterative process that occurs after initial capsule design, using the simulation results as a guide to modify the final design.
Research attracts attention at conferences
Mayeur recently presented his work at the World Congress on Computational Mechanics (WCCM) in Vancouver, British Columbia, Canada. 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 AMPM conference in Pittsburgh, Pennsylvania.
“This was one of the first attempts to utilise 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 additional research and findings at the upcoming 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.
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