Enhancing tribological properties of WS2/NbC/Co-based self-lubricating coating via laser texturing and laser cladding two-step process

Abstract

In order to avoid decomposition of solid lubricants during laser processing and improve the lubrication stability of laser-clad self-lubricating coating, a novel multilayer structural WS2/NbC/Stellite 6 metal matrix self-lubricating coating (MMSC) with laser texturing layer (LTL), lubricant layer (LL) and laser-clad sealing layer (LSL) was fabricated on Cr12MoV steel via laser surface texturing (LST) and laser surface cladding (LSC) two-step process. The microstructure, phase and tribological properties of the multilayer structural MMCC were investigated by means of optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy, as well as dry sliding wear test in wide-temperature (room temperature, 200 °C, 400 °C, and 800 °C). Results show that the multilayer structure partially inhibited the decomposition of the lubricant so that WS2 particles retained in the coating and NbC promoted the formation of a new lubricating phase CrS in decomposed WS2. The multilayer structural coating prepared in two steps had lower friction coefficient (0.226) and wears volume (31.916 mm3) at room temperature (RT). Moreover, the friction coefficient of the multilayer WS2/NbC/Co-based self-lubricating coating was still low (0.306) at 800 °C, only. Adhesive wear was identified as the main wear mechanism and the discrepancies of tribological properties were found to be mainly dependent of the kind of lubricating films generated at the wear surface.