Microstructure evolution and tribological properties of Co-based-VN alloy-Ti composite coatings by aging treatment

Laser cladding Co-based-VN alloy-Ti composite coatings was aging treated at 550 °C, 650 °C and 750 °C, respectively. The phase constituents, microstructure, microhardness and wear resistance of Co-based-VN alloy-Ti composite coatings after aging treatment were investigated systematically. The results showed the phase constituents of Co-based-VN alloy-Ti composite coatings were not affected before and after aging treatment at 550 °C and 650 °C, and σ-FeV phase disappeared after aging treatment at 750 °C. The intensities of Cr23C6, TiN and VC diffraction peaks were gradually improved as aging temperature increased. Number of short rod-shaped dendrites and equiaxed grains dispersed in the Co-based-VN alloy-Ti composite coatings was gradually improved as aging temperature increased, the distribution of the microstructure was more uniform, and the dislocation density was decreased. The microhardness and wear resistance of Co-based-VN alloy-Ti composite coatings were firstly reduced and then increased as aging temperature increased, the microhardness was increased by 7.9%, and the wear loss was reduced by 8.4%, for aging treatment at 750 °C. The abrasive mechanism of Co-based-VN alloy-Ti composite coatings after aging treatment was the abrasive wear.