Effects Of Load/Temperature On Wear Behaviors Of Ni-based Composite Coating Prepared By Laser Cladding On Titanium Alloy

In this paper, the Ti2Ni/α(Ti) dual-phase coating reinforced by TiB and TiC was fabricated on the Ti6Al4 V substrate by laser cladding. The Ti2Ni/TiNi dual-phase coating reinforced by Ti B and TiC was also fabricated. To solve the problem of the research lack on the gradient microstructure of Ni-based composite coatings, microstructural evolution and wear behaviors of laser cladding Ti2Ni/α(Ti) dual-phase coating reinforced by TiB and TiC was studied. Due to the insufficiency of research on high temperature microstructure of Ni-based composite coatings, high temperature wear behaviors of laser clad composite coatings prepared on titanium alloy substrates was studied.The results of microstructural evolution and wear behaviors of laser cladding Ti2Ni/α(Ti) dual-phase coating reinforced by TiB and Ti C indicated that phase constituents were confirmed by a theoretical prediction combined with X-ray diffraction(XRD) analyses. From the surface to the bottom of the coating, the reinforcements’ microstructure presented a regular evolution, namely TiCp+(TiB+TiC)e,(TiB+TiC)e and TiBp+(Ti B+TiC)e. Among them, TiCp and TiBp grew into dendritic and needle shapes, respectively, while TiB and TiC in the eutectic structure were liable to growing into flower-like and equiaxed shapes, respectively. The coating possessed the higher microhardness than that of the substrate. The average hardness of the coating was 752.6 HV0.1 which is significantly higher than that of the substrate(368 HV0.1). A quantitative calculation formula was established by a mathematic model to predict wear losses under different sliding time and applied loads in a definite precision. The wear mechanism was transformed from brittle debonding(at 10 N) to the joint action of brittle debonding and micro-cutting(at 20 N and 30 N) due to the microstructural evolution across the depth from the surface of the coating.The results of high temperature wear behaviors of laser clad composite coatings prepared on titanium alloy substrates showed that the variations in microstructure of the coatings at the three temperatures were insignificant. Wear resistance of the substrates was obviously enhanced after laser cladding at three temperatures. When the temperature was increased from 25 °C to 200 °C, wear mechanism was transformed from the micro-cutting into the joint action of dominant micro-cutting and slight oxidation wear. There was no significant difference in wear loss. When the temperature was further increased to 600 °C, serious oxidization occurred at the coating surface, resulting in serious wear loss of the coating. Wear mechanism was transformed into serious oxidization wear and slight micro-cutting.