Research on the Microstructure of Laser Remelted As-sprayed TiB₂-TiC_0.3N_0.7 based Composite Coating

Abstract

Ceramic coatings with excellent properties of wear resistance, corrosion resistance, oxidation resistance, stability in acid and alkaline environments, and good bond strength with a metallic substrate, are widely used in different industries. Air plasma spraying has high energy and efficiency for depositing ceramic materials with a high melting point. Due to intrinsic porosity and mechanical bond strength between coating and substrate, laser remelting technology can be applied to the coating surface for improving coating properties. As-sprayed TiB2-TiC0.3N0.7-based composite coating was surface remelted by laser. The surface roughness of as-sprayed and laser-remelted coatings was measured. The phase composition and the microstructure as well as the Vickers microhardness of coatings were studied by X-ray diffractometer (XRD), scanning electron microscopy (SEM), and Vickers indentation instrument. It is found that the phase composition does not change after laser remelting. However, the surface roughness of laser-remelted coating is smoother than that of as-sprayed coating. And the microhardness on the cross-section is increased after laser remelting. There is a micro-crack in the laser-remelted coating due to the fast heating and cooling of the laser. The microhardness of the laser-remelted coating is increased with bimodal Weibull distribution.