Effect of vacuum heat treatment on tribological properties of metal-doped CuS/MoS2 coating

The tribological properties of metal-CuS/MoS2 composite coatings were improved by selecting the metal materials and optimizing the heat treatment process. The composite coatings were prepared by magnetron cosputtering of copper or aluminum metals, CuS, and MoS2. Then, the prepared Cu-CuS/MoS2 and Al-CuS/MoS2 were subjected to vacuum heat treatment at 220, 320, and 420 C. The structure and tribological properties of the composite coatings were analyzed by scanning electron microscope, energy spectrum, x-ray diffraction, Raman spectrum, and multifunction friction tester. The results showed an island-like growth and a dense noncylindrical cross-sectional morphology of the metal-CuS/MoS2 composite coating. Metal- and CuS-doped MoS2 solid solution is a practical component in composite coatings. The wear scar of the composite coatings showed different color layers at different annealing temperatures due to composition deviation. After heat treatment at 320 C, the friction coefficient of Cu-CuS/MoS2 coating was reduced to a minimum of 0.08. After heat treatment at 420 C, the Al-CuS/MoS2 coating showed three different color layers of wear scar, and good tribological properties were obtained. The friction coefficient of the Al-CuS/MoS2 coating was as low as 0.06, and the adhesion of the Al-CuS/MoS2 coating was expressed in the HF1 level. The results show that the vacuum heat treatment can stimulate the action of CuS by forming a solid solution with MoS2, complementing the missing S atom during the sputtering deposition of MoS2 and improving the lubrication of the composite coating. In addition, although the action mechanisms are different, Cu and Al doping are all conducive to obtaining composite coatings with better tribological properties.