Hot Isostatic Pressing, or HIP, densifies materials. The process, completed in large containment vessels, involves pumping in a neutral gas under pressure while simultaneously exposing the material to a range of very high temperatures. The pressure and heat cause solid materials to flow together, improving the material's mechanical properties.
HIP can be used to post-process parts manufactured using conventional casting and powder metallurgy processes, as well as more recent additive manufacturing processes. During HIP, small cavities, or "pores," left in the materials after they are processed are filled in, improving the parts' mechanical properties. HIP is also a manufacturing process in and of itself. It can be used to sinter powders, effectively compacting them, and to assemble solid parts by diffusion welding. In addition to producing parts with excellent mechanical properties, HIP also stands out for its ability to produce parts with complex geometries and parts made from multiple—and sometimes incompatible—materials. It can also be used on parts of many different sizes. And, because HIP can reduce the number of machining and welding steps needed, it also saves on raw materials.
The CEA combines nearly 40 years of HIP know-how with expertise in design, modeling, and microstructural and mechanical characterization. This experience dates back to the early 1980s, when the CEA began exploring powder metallurgy for the manufacture of parts for nuclear power plants, a scope that was expanded to the aeronautics industry a decade later. A second process, HIP solid-state diffusion welding, was developed in 1996 to assemble solid parts for nuclear fusion reactors like ITER and for other reactor concepts. The CEA also still addresses aeronautics use cases, as well as molds and machine tools. CEA-Liten has been developing its diffusion welding know-how since 2005, when it first began manufacturing compact plate heat exchangers, initially for fourth-generation nuclear reactors. Today, these heat exchangers are finding new applications in renewable energy. They are proving particularly useful in P2X (power-to-X) solutions that use hydrogen and CO2 to produce methane. They are even being considered for emerging energy applications like hydrogen production.
CEA-Liten is currently engaged in the EQUIPEX+ CALHIPSO* project, coordinated by University of Burgundy Franche-Comté (UBFC). This project is developing custom HIP processes to meet the needs of manufacturers through a holistic approach that encompasses experimentation, modeling, and simulation. The project partners** are committed to driving growth in France's metallurgical industries. The goal is to develop a network of French HIP technology providers and create high-added-value jobs in the aeronautics, automotive, rail, energy, defense, and other strategic industries.
*This research is being funded in part by the French National Research Agency (ANR-21-ESRE-0039) as part of France's national economic stimulus program.
**CEA, Université Paris Sciences et Lettres (PSL), CNRS, FRAMATOME, Université de Bourgogne (UB), Université de Franche-Comté (UFC), Université Technologique Belfort-Montbéliard (UTBM).