Defects/CMAS corrosion resistance relationship in plasma sprayed YPSZ coating

This study aims to elaborate the effect of microstructural defects in plasma sprayed yttria partially stabilized zirconia (YPSZ) coating on its corrosion resistance to CaO-MgO-Al₂O₃-SiO₂(CMAS). The microstructural evolution of YPSZ coating under corrosion condition was comparatively studied. The results suggested that the defects that existed in the as-sprayed coating significantly decreased its corrosion resistance to CMAS. The penetration of CMAS could be effectively suppressed through depositing low-defected YPSZ coating by controlling the velocity and temperature of in-flight particles before they impacted onto the substrate. The dissolution of Y₂O₃into CMAS caused the phase transformation from the metastable tetragonal phase (t′-ZrO₂) to the monoclinic phase (m-ZrO₂) and some components in CMAS can act as sintering additives to accelerate the densification of coatings. The stress caused by the thermal gradient and sintering resulted in the initiation and propagation of coarse cracks, which were basically vertical to the coating surface. These vertical cracks can greatly promote the penetration of CMAS, and vice versa.