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

摘要

To enhance the wear resistance and friction-reducing capability of titanium alloy, a process of laser cladding γ-NiCrAlTi/TiC + TiWC_2/CrS + Ti_2CS coatings on Ti-6Al-4V alloy substrate with preplaced NiCr/Cr_3C_2-WS_2 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 tri-bological properties were evaluated using a ball-on-disc tribometer under dry sliding wear test conditions at 20 ℃ (room-temperature), 300 ℃, 600 ℃, respectively. The results show that the coating has unique microstructure consisting of α-Ti, TiC, TiWC_2, γ-NiCrAlTi, Ti_2CS and CrS phases. Average microhardness of the composite coating is 1005 HV_(0.2). which is about 3-factor higher than that of Ti-6Al-4V substrate (360 HV_(0.2)). 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 TiWC_2 carbides and the CrS and Ti_2CS sulfides which have excellent self-lubricating property.