High temperature self-lubrication anti-wear composite coatings on titanium alloy by laser cladding

To improve the tribological property of titanium alloy, γ-NiCrAlTi/TiC composite coatings and γ-NiCrAlTi/TiC/CaF₂ high-temperature self-lubrication composite coatings were fabricated on Ti-6Al-4V alloy by laser cladding technology. The constituents and microstructure of the fabricated coatings were examined by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) techniques, and the tribological properties were evaluated using a ball-on-disc tribometer under dry sliding wear test conditions at room-temperature, 300 ℃, 600 ℃, respectively. The results show that the bonding of the coatings to the substrates is completely metallurgical. The microstructure of the γ-NiCrAlTi/TiC/CaF₂ cladding coating is consisted of the “in-situ” synthesized small clump and needle shaped TiC particles,TiC dendrite, γ-NiCrAlTi solid solution and spherical CaF₂ particles. The wear rate of the fabricated coatings was greatly decreased mainly due to the combined effect of the wear-resistant TiC carbides and the ductile γ-NiCrAlTi matrix. Moreover, the average friction coefficient of γ-NiCrAlTi/TiC/CaF₂ coating was 0.21 at 600 ℃, which was reduced by 43 % and 50 % compared to the substrate and γ-NiCrAlTi/TiC coating, respectively. It indicates that γ-NiCrAlTi/TiC/CaF₂ coating has good friction-reducing and anti-wear properties at high temperature.