Abstract
Clean energy is a key factor in reducing carbon dioxide (CO2) emissions and ultimately combatting climate change. Rapidly increasing electricity demand in the developed world has created a great interest in improving and expanding the role of nuclear power in the power generation sector. Increasing reactor lifetime and efficiency is possible in advanced reactor designs by utlizing advanced materials. Materials that are able to withstand harsh nuclear reactor environments while maintaining operational properties have been a focus of nuclear scientific research and development. Advanced coatings have been utilized to protect bulk components from extreme environments, but face damage from many degradation causing factors including thermal and mechanical stresses, corrosion, diffusion and phase changes, and irradiation, therefor development of new materials and associated advanced manufacturing (AM) techniques for coatings is explored. Coating properties of various materials and designs are analyzed for overall build quality, microstructure, compositional distribution, phases analysis, and microhardness were studied by laser optical microscopy, scanning election microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), and Vickers microhardness techniques, and results are reported in the current work. Functionally graded materials (FGMs) allow for more resilient materials coatings by reducing material property mismatch between a desired bulk material and the environment-facing coating. Powder-based directed energy deposition (DED) techniques are used as a method to synthesize FGMs between three commonly industrial alloys: IN718, SS316L, and 70Co30Cr (commercially known as Stellite 21). Two of three FGMs were successful fabricated in this study and gradual changes in composition and resulting properties is observed over the build height of the FGM. Complex concentrated alloys (CCAs) are a system of alloys composition of nearly equiatomic elements, creating a state of high configurational entropy in the material. These alloys are of interest for various industrial applications due to their high strength and hardness, wide operational temperature range, creep and diffusion resistance, and radiation resistance. In the current work CoCrFeNi-base CCAs are synthesize by combining three common industrial alloys: IN718, SS316L, and 70Co30Cr (commercially known as Stellite 21). One bulk specimen is fabricated with a 1:1:1 ratio of IN718, SS316L, and 70Co30Cr where IN718 is a source of nickel and chrome, SS316 is a source of iron and chromium, and 70Co30Cr is a source of cobalt and supplemental chromium. Additionally, a FGM of the identified CCA system from SS316 was fabricated. Results show a successful CCA fabricated with this technique and a FGM of the CCA system from 316SS.