Material Synthesis and Advanced Manufacturing Without Melting – the Advantages of Bulk, High-Shear Processing

The next generation of materials synthesized, or assemblies fabricated, to solve challenges in power generation (molten salt or sCO2 thermal transfer systems, corrosion, creep/fatigue, higher temperature operation) will likely be highly tuned to their performance envelope. This often means very strict requirements on microstructure (homogeneity, grain size, texture, grain boundary phases) and very strict requirements on alloy chemistry and homogeneity; all of these to hit the new and challenging requirements for bulk mechanical performance and durability. Some of these new materials (ODS or HEAs for example) require special processes to synthesize them, or to fabricate and weld/join them. In many cases a process that melts and solidifies the material, or joins it by melting, can fail to make, or can destroy an existing optimized microstructure. Synthesis and fabrication methodologies that do not melt the materials can be the manufacturing process route of choice to preserve the character of these advanced materials.

Through specific examples, this talk will outline work that has shown where solid phase, high-shear processing has resulted in materials and semifinished product forms that show higher performance than their conventionally fabricated counterparts. Conventional materials processing methods often rely on thermodynamics-driven processes, like creating precipitate phases by prolonged heat treatment. The often kinetics-driven, non-equilibrium processes in high-shear processing can offer alternative routes to high performance microstructures.

Examples will also outline the potential for lower cost manufacturing routes due to fewer steps or lower embedded energy in the manufacturing process. This talk will outline some of the advances in high-shear extrusion processing (Friction Extrusion and ShAPE). The talk will also describe advances in solid-phase welding for next generation power plant materials (Friction Stir Welding), and it will describe efforts using solid-phase cold spray processes to demonstrate repair of power plant systems without the disadvantages that melt-based methods can sometimes introduce.