b'The postirradiation examination of Cr, CrN, and TiN coatings on SiC identified the key degradation process and provided feedback for improvement of coating performance.processing. The coating needs toelectron microscopy (SEM), and be free from significant debondingtransmission electron microscopy and cracking to avoid degradation(TEM) at the Low Activation Materials of the corrosion behavior and theDevelopment and Analysis (LAMDA) hermeticity of the coating under anLaboratory at ORNL. irradiation environment.The degradation process expected The test specimens included cathodicis debonding/delamination at arc physical-vapor-deposited (PVD)the interface of the coating and Cr, CrN, and TiN; electro-plated Cr;substrate as a result of irradiation-and vacuum-plasma-sprayed Zr.induced stress; stress is built up Neutron irradiation was conductedwhen the coating and substrate swell under LWR-relevant temperaturedifferently under irradiation. This and dose conditions (at 300C todamage mechanism is a well-known 4.81024 n/m2 [>0.1 MeV],challenge for dissimilar interfaces equivalent to nominal neutronunder irradiation; it also applies to damage of ~0.5 displacements perSiC/coatings, as SiC swells by up to atom) under an inert Ar atmosphere~2 % in volume at 300C. Therefore, at the Massachusetts Institute ofthe technical goal of the coating Technology reactor (MITR). Multiscaledevelopment is to achieve a high-microstructural characterizations wereadhesion-strength and/or ductile conducted using optical microscopy,coating that withstands such swelling-x-ray diffraction (XRD), scanninginduced stresses.2019|AFC ACCOMPLISHMENTS 87'