Preparation and high temperature tribological properties of laser in-situ synthesized self-lubricating composite coatings containing metal sulfides on Ti6Al4V alloy

Abstract

The composite coatings were prepared on Ti6Al4V alloy with preplaced mixed Ni60-TiC-WS2 powders by laser cladding. The microstructure, phase compositions and tribological properties as well as the corresponding wear mechanisms of the composite coatings at 20, 300, 600, 800 °C were analyzed systematically. The results indicate that the microhardness of the composite coatings is higher than that of the substrate. Due to the synergetic effects of the in-situ synthesized solid lubricants and hard phases, both the wear resistant and friction reducing capabilities of the composite coatings are better than that of the substrate at all experimental temperatures. With the increasing of temperature, the friction coefficients and wear rates of the composite coatings and the substrate all decrease. Moreover, when the composition of cladding powders is Ni60–16.8% TiC-23.2%WS2 (wt%), the friction coefficients is 0.321 and wear rates are 2.9 × 10−5 mm3/Nm at 800 °C. The plastic deformation and delamination as well as oxidation wear are main wear mechanisms of the substrate at 800 °C, while the composite coatings is predominated by the oxidation wear and slight adhesive wear at 800 °C.