Development and characterization of laser clad high temperature self-lubricating wear resistant composite coatings on Ti–6Al–4V alloy

• A novel high temperature self-lubricating anti-wear composite coating was fabricated.
• Reinforced carbides as well as self-lubricating sulfides were in situ synthesized.
• Microhardness of the Ti–6Al–4V substrate was significantly improved.
• Friction coefficient and wear rate of the composite coating were greatly reduced.

To enhance the wear resistance and friction-reducing capability of titanium alloy, a process of laser cladding γ-NiCrAlTi/TiC + TiWC2/CrS + Ti2CS coatings on Ti–6Al–4V alloy substrate with preplaced NiCr/Cr3C2–WS2 mixed powders was studied. A novel coating without cracks and few pores was obtained in a proper laser processing. The composition and microstructure of the fabricated coating were examined by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) techniques, and tribological properties were evaluated using a ball-on-disc tribometer under dry sliding wear test conditions at 20 °C (room-temperature), 300 °C, 600 °C, respectively. The results show that the coating has unique microstructure consisting of α-Ti, TiC, TiWC2, γ-NiCrAlTi, Ti2CS and CrS phases. Average microhardness of the composite coating is 1005 HV0.2, which is about 3-factor higher than that of Ti–6Al–4V substrate (360 HV0.2). The friction coefficient and wear rate of the coating are greatly decreased due to the combined effects of the dominating anti-wear capabilities of reinforced TiC and TiWC2 carbides and the CrS and Ti2CS sulfides which have excellent self-lubricating property.