Microstructure characterization of in-situ ZrC composite coating with graceful toughness and improved tribological properties prepared by plasma spraying

Abstract

Substantial brittleness is still a problem to be solved for ceramic coatings. ZrC composite coating was prepared by plasma spraying ZrO2-SiC-Al composite powder utilizing in-situ reactions. As a comparison, ZrC-ZrSi2-Al2O3 composite powder was also used to prepare ZrC composite coating by plasma spraying via ex-situ approach. The reactions occurred in ZrO2-SiC-Al system during the plasma spraying process could be described as the thermite reaction between ZrO2 and Al and the self-propagating reaction between Zr and SiC. The corresponding formation mechanism of the composite coatings were also revealed. The resultant materials could melt fully under the effect of the plasma jet and the exothermic reactions. In-situ fabricated ZrC composite coating was featured with higher densification and better interlayer compactness compared to the coating prepared by ex-situ method. In-situ generated fine-grained microstructure, which was further confirmed by TEM, was homogenously distributed in the coating prepared by ZrO2-SiC-Al composite powder. Elevated toughness and excellent wear resistance observed in the coating prepared by plasma spraying ZrO2-SiC-Al composite powder could be attributed to the denser microstructure tailored by in-situ reactions.