Characteristics of laser clad α-Ti/TiC+(Ti,W)C_1−x/Ti₂SC+TiS composite coatings on TA2 titanium alloy

TiC reinforced Ti matrix composite coating with Ti₂SC/TiS lubricant phases in-situ synthesized were prepared on TA2 titanium alloy by laser cladding with different powder mixtures: 40%Ti-19.5%TiC-40.5%WS₂, 40%Ti-25.2%TiC-34.8%WS₂, 40%Ti-29.4%TiC-30.6%WS₂ (wt%). The phase compositions, microstructure, microhardness and tribological behaviors and wear mechanisms of coatings were investigated systematically. Results indicate that the main phase compositions of three coatings are all continuous matrix α-Ti, reinforced phases of (Ti,W)C_1−x and TiC, lubricant phases of Ti₂SC and TiS. The microhardness of the three different coatings are 927.1 HV_0.5, 1007.5 HV_0.5 and 1052.3 HV_0.5, respectively. Compared with the TA2 titanium alloy (approximately 180 HV_0.5), the microhardness of coatings have been improved dramatically. The coefficients of friction and the wear rates of those coatings are 0.41 and 30.98×10⁻⁵ mm³ N⁻¹ m⁻¹, 0.30 and 18.92×10⁻⁵ mm³ N⁻¹ m⁻¹, 0.34 and 15.98×10⁻⁵ mm³ N⁻¹ m⁻¹, respectively. Comparatively speaking, the coating fabricated with the powder mixtures of 40%Ti-25.2%TiC-34.8%WS₂ presents superior friction reduction and anti-wear properties and the main wear mechanisms of that are slight plastic deformation and adhesive wear.