Investigation of laser cladding high temperature anti-wear composite coatings on Ti6Al4V alloy with the addition of self-lubricant CaF2

To improve the high-temperature tribological properties of Ti-6Al-4V alloy, γ-NiCrAlTi/TiC and γ-NiCrAlTi/TiC/CaF2 coatings were fabricated on Ti-6Al-4V alloy by laser cladding. The phase compositions and microstructure of the coatings were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). The tribological behaviors were evaluated using a ball-on-disk tribometer from ambient temperature to 600 °C under dry sliding wear conditions and the corresponding wear mechanisms were discussed. The results indicated that the γ-NiCrAlTi/TiC/CaF2 coating consisted of α-Ti, the “in situ” synthesized TiC block particles and dendrite, γ-NiCrAlTi solid solution and spherical CaF2 particles. The wear rates of γ-NiCrAlTi/TiC/CaF2 coating were decreased greatly owing to the combined effects of the reinforced carbides and continuous lubricating films. Furthermore, the friction coefficients of γ-NiCrAlTi/TiC/CaF2 coating presented minimum value of 0.21 at 600 °C, which was reduced by 43% and 50% compared to the substrate and γ-NiCrAlTi/TiC coating respectively. It was considered that the γ-NiCrAlTi/TiC/CaF2 coating exhibited excellent friction-reducing and anti-wear properties at high temperature.