Microstructure and properties of Ni-based VC and TiVC2 composite coatings fabricated in situ by laser direct deposition

Ni-based VC and TiVC2 composite coatings were prepared on the surface of worn brake discs by laser direct deposition, and the influence mechanism of trace TiC addition on the microstructure and performance of the coating was investigated. The microstructure of the coatings was analyzed by XRD, SEM, EDS, and TEM, which revealed the evolution mechanism of the microstructure during the laser deposition process. The friction wear performance was tested on friction wear equipment. The results showed that VC0.88 was formed by the in-situ reaction of C and V under the action of the laser, which presents dendritic morphology. After the addition of TiC particles, TiVC2 was further synthesized along the TiC particles in addition to dispersed VC0.88 in the coating. It can be seen that the addition of trace TiC particles inhibited the formation of VC0.88 dendrites and enhanced the plastic toughness of the coating. HRTEM calibration proved the existence of TiVC2 and Ni, and there was no obvious orientation relationship between the interface. The friction coefficients of Ni-based VC and Ni-based TiVC2 coatings with Al2O3 balls were 0.59 and 0.51 at room temperature, respectively. After 1.5 h of high-temperature wear at 300 °C and 600 °C, the distribution of wear marks shows a groove and high-temperature fatigue appearance. The TiC-doped coating has better wear properties than the base material and the original coating is expected to meet the requirements for brake discs.