TiC in-situ strengthening mechanism and crack initiation mechanism of SiC/TC4 composite coatings by laser cladding

Abstract

SiC/TC4 composite coatings were fabricated successfully on the TC4 surface by varying the laser power, and the effect of TiC in-situ strengthening on the microhardness and wear resistance of coatings was investigated. The results show that SiC is continuously decomposed to generate TiC in situ, and α martensite in the coating is refined at 1000 W, with less TiCm. α martensite in the coating is roughened at 1900 W, with the highest content of TiC dominated by dendritic TiCd and petal-like TiCf, longitudinal cracks emerged from the bonding zone and penetrating through the coating. While the appropriate laser power well balanced the relationship between α-martensite and in situ precipitated phases. The C16 coating has the best performance, with an average microhardness 2.1 times higher than that of the substrate (351.8 HV0.2) and a wear rate of 38.1% of the substrate, respectively. The wear mechanism of the substrate is abrasive, oxidative and fatigue wear, and the wear mechanism of C16 is mainly abrasive wear. The change of the mechanism is due to the fact that TiC particles play the role of skeleton and support in the coating, which are uniformly distributed around α-martensite, thus inhibiting the plastic deformation of the coating.