ORNL Combines 3D Printing and HIP to Create Large Metal Parts

As the demand for large-scale metal parts continues to rise across sectors such as clean energy, aerospace, and defense, the Department of Energy’s Oak Ridge National Laboratory (ORNL) is spearheading research to re-establish U.S. manufacturing dominance in this area. Through advancements in powder metallurgy-hot isostatic pressing (PM-HIP), paired with additive manufacturing (AM) techniques, ORNL is offering what it considers a high-precision alternative to traditional casting and forging methods.

With conventional casting and forging capabilities having largely shifted overseas, the U.S. faces supply chain challenges for components exceeding 10,000 pounds. ORNL’s research is exploring PM-HIP as a solution, leveraging 3D printing for enhanced process control and geometric complexity. The process involves fabricating pre-formed molds—or “cans”—using wire arc additive manufacturing (WAAM) and hybrid additive-subtractive methods, which are then filled with metal powders.

The sealed molds undergo heating and pressurization cycles in a hot isostatic press (HIP). Unlike traditional methods, this solid-state bonding process consolidates metal powders into dense, complex geometries without melting, allowing for tighter tolerances and reduced porosity. This approach not only offers design flexibility but also opens the door for multi-material builds, critical for applications in sectors with stringent performance requirements.

Addressing Shrinkage and Consistency with Computational Modeling

One of the primary technical hurdles in PM-HIP is managing the volumetric shrinkage of the metal powders, which can reach up to 30% during consolidation. This shrinkage often varies with the complexity of the component geometry, posing challenges for maintaining dimensional accuracy. Senior research scientist Jason Mayeur, specializing in computational solid mechanics, has developed predictive models to simulate how shrinkage behaves across different geometries. His simulations guide iterative adjustments to the initial mold design, ensuring that the final part meets precise specifications.

“PM-HIP offers a controlled pathway for producing large-scale metal parts that have become increasingly difficult to source through conventional methods,” Mayeur notes. His modeling efforts help refine the process by predicting deformation characteristics and optimizing heat and pressure cycles for different alloys.

Complementing Mayeur’s computational focus, metallurgist Soumya Nag conducts experimental research on the PM-HIP process, concentrating on the fabrication of AM-based capsules and the evaluation of resulting part quality. Nag’s work involves testing the mechanical properties of metal powders, ensuring that the materials perform reliably under the demanding conditions of the HIP process. His expertise in characterizing microstructures and assessing high-temperature alloys supports the development of robust PM-HIP procedures.

“By combining the design flexibility of additive manufacturing with the reliability of PM-HIP, we can produce large-scale, custom parts tailored for energy and defense applications,” says Nag. The collaboration between computational predictions and empirical testing enables ORNL to push the boundaries of what is possible with PM-HIP, ensuring that it meets the exacting standards required for critical infrastructure.

Strategic Industry Applications and Decarbonization Goals

PM-HIP’s ability to produce high-integrity metal parts domestically could help the U.S. reduce its dependency on foreign suppliers, a crucial step in enhancing supply chain resilience. For the nuclear, hydroelectric, and aerospace sectors, PM-HIP provides a method to manufacture large, complex components like pressure vessels and impellers with enhanced material properties, such as improved toughness and resistance to thermal fatigue.

Moreover, ORNL’s advancements align with the U.S. Department of Energy’s focus on decarbonization. The PM-HIP process enables the use of high-performance materials in energy generation and distribution infrastructure, supporting the transition to more efficient, lower-emission systems. The potential to locally produce such components can also reduce the carbon footprint associated with overseas transport and extended supply chains.

To address the remaining technical challenges and accelerate industry adoption, ORNL is hosting a PM-HIP workshop on October 9-10, 2024, at its Manufacturing Demonstration Facility (MDF). Supported by the Metal Powder Industries Federation and the Electric Power Research Institute, the event aims to bring together manufacturers, researchers, and policymakers. The workshop will focus on collaborative efforts to refine PM-HIP processes and expand their applicability across various industries.

This event is part of a broader initiative by ORNL, supported by the Department of Energy’s Advanced Materials and Manufacturing Technologies Office (AMMTO), to promote advanced manufacturing solutions. By fostering closer industry-academic ties and identifying targeted research needs, the workshop seeks to drive the technology closer to commercialization.