ICME development of a cold spray enabled corrosion resistant bimetallic structure for nuclear reactors

The bimetallic structure concept consisting of a corrosion resistant surface layer joined on top of an ASME code-approved substrate becomes a promising solution to address the corrosion issue of ASME substrate materials in molten salt environment. Specifically, refractory materials such as molybdenum, tungsten, and alloys containing them are found to be most resistant in molten salt environment and hence they have great potential to be used as the salt-facing surface layer. Due to the well-recognized difficulties of welding/printing refractory materials (i.e., oxidation, brittle phase formation, cracking, etc.), cold spray, a deposition technology that minimizes material heating, avoids undesired thermal effects and maintains dimension stability, is an ideal approach for fabricating the bimetallic components. Under this SBIR Phase II program, QuesTek Innovations LLC, a leader in the field of Integrated Computational Materials Engineering (ICME) and 2016 Tibbetts Award recipient, will continue partnering with Solvus Global and Cal Poly Pomona to design, fabricate and validate cold spray enabled bimetallic structures, consisting of a refractory-based corrosion resistant surface layer and an ASME code-certified substrate, for molten salt reactors (MSR). In Phase I, the team has successfully designed and fabricated proof-of-concept bimetallic materials using SS316 as substrate that experimentally exhibited excellent deposition quality, interface adhesion and corrosion resistance. During the Phase II program, the ICME materials design and cold spray processing technology demonstrated in Phase I will continue to be developed and optimized, in tandem with implementing an additional approach of functionally graded materials (FGM) to further improve the robustness and performance of the cold-sprayed structure for nuclear applications. QuesTek will continue applying its ICME materials design methodologies to refine the refractory surface layer compositions developed in Phase I and explore new designs. In addition, QuesTek will be developing and implementing a computational gradient design framework to assist in designing FGM pathways with optimized performance of the bimetallic structure. Solvus Global, a leading company dedicated to advanced cold spray technology, will continue to lead the cold spray related tasks. They will develop the powder materials defined by QuesTek’s computational modeling, optimize cold spray processing parameters, manufacture bimetallic materials, including functionally graded structure, and conduct detailed metallurgical characterization and adhesion tests on the fabricated materials. Prof. Vilupanur Ravi at Cal Poly Pomona (CPP) is a distinguished professor with extensive experience in materials degradation in molten salt environment. His group will continue to perform detailed and carefully designed molten salt corrosion tests and characterization. Towards the end of the 2-year Phase II program, the team will work to further scale-up production efforts based on the down-selected material systems. The target batch size for initial production-level readiness will be on the order of 20-100lbs per batch.