Effects of MoS₂ on Mechanical Properties and Tribological Behavior of DLC Films

In the harsh ocean environment, the traditional single diamond-like carbon (DLC) films can no longer meet the performance requirements of anti-friction and wear resistance, while element doping has become an important method to improve the tribological properties of DLC films. In order to improve the performance of DLC films deposited on 304 stainless steel by using DC magnetron sputtering technology, they were doped with MoS₂. The effect of MoS₂ on tribological properties of the DLC films in the atmospheric environment, deionized water and artificial seawater environment were studied. SEM and EDS were used to characterize surface morphology and element content of the films. XPS and Raman were used to examine valence state and microstructure of the elements of the films. In addition, mechanical and tribological properties of the films were tested by using nanoindentation and friction testing machines. It is showed that there were no holes and cracks in the films and the microstructure was uniform and compact. The maximum hardness of the films was about 10 GPa and the elastic recovery rate reaches 56.8%. With increasing sputtering power of MoS₂, the friction coefficient of the films increases gradually. In the three environments, the friction coefficient and wear rate of DLC-MoS₂-40 film were the lowest, with friction coefficients to be about 1/7, 1/6 and 1/6 of 304 stainless steel and the wear rate to be about 1/10, 1/3 and 1/3 of 304 stainless steel, respectively. The doping of MoS₂ could effectively improve the friction and wear properties of stainless steel matrix coated with diamond-like carbon films.