SiC/SiC composites have gained significantattention as accident tolerant fuel cladding for their hightemperature mechanical properties and superioroxidation kinetics in accident scenarios. However,operational LWR coolant and irradiation conditionscause issues regarding SiC matrix dissolution and fissionproduct retention respectively. A potential solution is theapplication of a dual-purpose (environmental barrier andhermetic seal) coating. The goal of this research is to aidin the down-selection process in identifying the highestperformance coating for LWR conditions. One of the mostimportant selection criteria is the coating-substratemechanical stability. This research presents aninvestigation of the relationship between fracture strengthand microstructure through small scale mechanicaltesting and TEM analysis. Micro-cantilevers werefabricated across the SiC/coating interfaces on severalcandidates including PVD Cr and CrN. Testing wasperformed at ambient and 320°C. The lower-boundaverage ambient failure strength for the SiC/Cr andSiC/CrN interfaces were on the order of 3.2 Gpa and 3-5Gpa respectively. High temperature tests revealed adramatic reduction in strength, around 0.4GPa. Neutronirradiated SiC/Cr interfaces (～0.5dpa at 330°C) showedslightly reduced failure strength of 2.9 Gpa at ambienttemperature. A TEM investigation compared irradiatedand pristine SiC/Cr interfaces.
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