Abstract:The composite coating NiCr-Ag was successfully prepared by lase clad on substrate of pure Ti in order to enhance space tribological properties of pure Ti, with hard phase NiCr as the reinforcing agent and Ag as the primary lubricating fillers. The composition and microstructure of the fabricated composite coating were investigated by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and high-resolution transmission electron microscopy (HRTEM). Furthermore, the space tribological properties were systematically evaluated by a ball-on-disc tribometer against AISI-52100 ball counterpart under simulated space environment including atomic oxygen (AO), ultraviolet irradiation (UV), and high vacuum (VC) in comparison with that in atmospheric environment (AR) through the space tribological test system. The results show that the composite coating has better tribological properties in atmospheric environment than those in simulation space environment. Findings indicate that the vacuum (without any moisture or hydrocarbons) and intense radiation in the space environment would induce severe oxidation on the surface of the coating, making the enhancement of the coating weak and the lubrication effect deteriorated. The wear mechanism is abrasive wear under atmospheric environment. Adhesion wear and plastic deformation are the predominant wear mechanism under space environment as peeling pits and transferred Ni, Cr, and Ti could be found on the worn surface and the surface of the counterpart, respectively.