Effects of laser remelting on microstructure and solid particle erosion characteristics of ZrO2–7wt%Y2O3 thermal barrier coating prepared by plasma spraying

In this study, the influences of laser remelting on microstructural characteristics, microhardness, and solid particle erosion behavior of MCrAlY/ZrO2–7wt%Y2O3 double-layer structure thermal barrier coatings prepared by plasma spraying were examined. The erosion failure mechanisms of the as-sprayed and laser-remelted coatings were investigated. Results show that the plasma-sprayed coating has a typical lamellar stacking characteristic with high porosity. The surface lamellar defect of the as-sprayed coating was erased, and the compactness of the coating improved significantly after laser remelting. The laser-remelted coating consisted of a remelted layer with a dense column-like crystal structure, a heat-affected layer with a more dense structure than that of the as-sprayed coating, and a remaining plasma-sprayed layer. The microhardness and erosion resistance of the laser-remelted coating are considerably better than the as-sprayed one. The spalling of the sprayed splats from the lamellar interface and crushing of brittle ceramic coating are mainly attributed to the erosion failure of the plasma-sprayed coating. By contrast, cracks occurred in the region near the surface of the laser-remelted layer, and the erosion occurred mainly because of the removal of these small blocks. The laser-remelted coating has evident micro-cutting marks and some ductile erosion characteristics.