Tribological Behavior Of Plasma Sprayed MoS₂/Cu Composite Coating In Vacuum

MoS₂/Cu base composite coating was deposited by air plasma spraying on2A12aluminum alloy substrate using commercial Cu-MoS₂（MoS₂-70mass.%Cu） compositepowder as raw material. Microstructure, phase composition, component distribution andwear surface of coating were characterized by scanning electron microscopy （SEM）,energy dispersive spectrometer （EDS）, X-ray diffraction （XRD） and Raman spectra. Theproperties, such as porosity, microhardness, bond strength and thermal diffusivity, werealso examined. Tribological properties of as-sprayed coating were explored by usingGTM-3E ball-on-disc vacuum friction and wear instrument.The results show that the composite coating has a typical layered structure, MoS₂particles are evenly distributed in the coating. The structure of coating is comparativelydense and firmly bonded with aluminum matrix. The coating mainly consists of Cu, MoS₂and Cu2O phase. The porosity detected based on Archimedean method and the averagemicrohardness （HV0.05） is about16.4%and102（±5）, respectively. The average bondstrength is24.3（±0.5） MPa. The thermal diffusivity of composite coating is relativelystable in the range of25℃-250℃.The main reason lies on the different thermalconductivity mechanism. The above results indicate that plasma spraying technology canbe used to deposit the MoS₂/Cu Composite coatings.Under test conditions, composite coating show excellent friction reducing effect, andthe friction coefficient were in the range of0.05to0.15. In vacuum environment, with thefriction velocity and load increase, the distribution of MoS₂on coating friction surface wasincreased and its adsorption with copper was improved. It can improve MoS₂selflubricating film layer integrity and stability in friction process, effectively reducing thefriction coefficient of the coating. The friction coefficient of MoS₂/Cu base compositecoating decreases with the increase of applied friction velocity from0.5m/s to2.5m/s andload from5N to25N.The wear mechanism study showed that the adhesive wear of Cu material in thefriction process was significantly reduced by forming a MoS₂self lubricating film. Fatiguefall off caused by cycle stress in the friction process was the main wear mechanism of MoS₂/Cu base composite coating. The wear rate of MoS₂/Cu base composite coatingincreases with the increase of applied friction velocity from0.5m/s to2.5m/s and loadfrom5N to25N.Obviously, MoS₂/Cu base composite coating has a good vacuum tribologicalproperties and broad prospects for practical application.