b'2.3 LWR CORE MATERIALSProgress in development and characterizationof coatings for SiC/SiC claddingPrincipal Investigator: Peter Mouche (ORNL)Team Members/ Collaborators: Peter J. Doyle (UTK), Takaaki Koyanagi (ORNL), Stephen S. Raiman (ORNL) and Yutai Katoh (ORNL)Testing of variousS ilicon carbide (SiC) fiber rein- crack propagation through the coating, forced SiC matrix compositesand how any cracking will affect coating depositionprovide many potential benefitscorrosion needs to be investigated. By methods identified theas compared to traditional zirconium- understanding the fundamentals of residual stress range atbased alloys for light water reactorthese processes, a robust coating can which Cr coatings will(LWR) fuel cladding. However,be created. This will bring SiC/SiC remain adherent and aseveral technological barriers stillcomposites one step closer to being able microstructural methodneed to be overcome before it can beto be deployed and realizing its potentail to increase crackimplemented making it a high-risk,advantages as a more stable cladding. resistance. high-reward goal. HydrothermalExperiments focused on characterizing corrosion and loss of hermiticitytwo main physical vapor deposition due to crack networking are the(PVD) coating architectures two issues targeted by developingdeposited on monolithic SiC. The coatings on SiC. Previous corrosionfirst were hybrid high power impulse and irradiation work at Oak Ridgemagnetron sputtering (HiPIMS) National Laboratory (ORNL) identi- combined with cathodic arc deposited fied pure Cr as a promising materialby Acree Technologies Inc. to test over other ceramic coatings. Thecrack resistant coatings with bimodal major challenge is solving tensilemechanical properties that are single stress build up in the coating fromphase (Figure 1). Specimens with radiation induced swelling of SiC. Thispre-cracked coatings were exposed swelling mismatch between the SiCto various LWR water chemistries and the coating can lead to crackingfor 500 hours to determine if oxide or delamination of the coating.formation could heal cracks if they Multiple Cr coatings were deposited toform during service. The second investigate pathways to mitigate crackset of coatings were DC magnetron formation in the coating as well as thesputtering (DCMS) coatings, deposited corrosion response if cracks do form. at Manchester Metropolitan University Project Description:(MMU), to determine how much The objective of this work is tocompressive residual stress can be understand the effects of depositionfabricated into coatings to offset the parameters on the morphology ofSiC swelling. The coating properties, coatings on SiC, and leverage this toas measured by transmission electron design a coating that is specific tomicroscopy (TEM), scanning electron the needs of nuclear. As SiC swellsmicroscopy (SEM), x-ray diffraction under neutron irradiation the range(XRD) residual stress measurements, of stresses a coating can withstand,and nano-indentation were related 62 2020|AFC ACCOMPLISHMENTS'