Additive alternative to casting and forging could help reshore large component manufacturing

Oak Ridge researchers explore using powder metallurgy-hot isostatic pressing to revitalize domestic production of very large metal parts.

Researchers at Oak Ridge National Laboratory (ORNL) are using advanced manufacturing techniques in an effort to revitalize the domestic production of very large metal parts that weigh at least 10,000 pounds each.

Senior research scientists Jason Mayeur and Soumya Nag are exploring the viability of an alternative to casting and forging known as powder metallurgy-hot isostatic pressing (PM-HIP), introducing process improvements, including the use of 3D-printing methods such as wire-arc additive manufacturing (WAAM) and hybrid  manufacturing, as well as in-situ monitoring and advanced computational modeling.

According to the researchers, these techniques can create PM-HIP molds faster and more accurately than conventional processes. This approach could make PM-HIP more precise and effective as well as more affordable.


“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 in a press release. “The technology is of particular interest to the nuclear and hydroelectric industrial sectors, as well as the Department of Defense.”

Improving the PM-HIP process

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 before applying a more permanent hermetic seal.

The capsule is then heated and pressurized in prescribed cycles within a hot isostatic press. Without melting, these cycles facilitate the consolidation of the metal powder into the required shape via solid-state bonding. When the bonding is complete, acid leaching or machining is used to remove the exterior can, revealing the part.

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 in an iterative process that occurs between the initial capsule design and the final design, using the simulation results as a guide to modify it.

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.

On October 9-10, 2024, ORNL — along with the Metal Powder Industries Federation and the Electric Power Research Institute — will host a PM-HIP Workshop at the ORNL Manufacturing Demonstration Facility. The goal of this workshop is to identify the key challenges currently inhibiting the broader adoption of the approach.

Written by

Ian Wright

Ian is a senior editor at engineering.com, covering additive manufacturing and 3D printing, artificial intelligence, and advanced manufacturing. Ian holds bachelors and masters degrees in philosophy from McMaster University and spent six years pursuing a doctoral degree at York University before withdrawing in good standing.