Structure, mechanical and tribological properties of MoSN/MoS2 multilayer films

Abstract

MoSN/MoS2 multilayer films were deposited by a sputtering MoS2 target in alternate Ar and Ar/N2 mixed atmospheres with different nitrogen flow rates. The influence of nitrogen flow rates on the microstructure, mechanical and tribological properties of the prepared films were investigated. The multilayer film exhibited the preferred orientation of (002) plane for MoS2 sublayers and amorphous structure for MoSN sublayers. Introducing N2 into the source gas resulted in a much more compact structure for multilayer films due to the suppression of columnar growth of MoS2 film. With the increase of the nitrogen flow rate, the hardness of the multilayer film firstly increased from 2.3 to 10.5 GPa as the nitrogen flow rate increased from 4 to 10 sccm and then turned downwards to 6.5 GPa at 20 sccm. MoSN/MoS2 film deposited with an optimized microstructure exhibited low friction coefficients below 0.03 and a wear life higher than 1.8×105 revolutions in vacuum. Meanwhile, the optimized film showed an ultralow friction coefficient of 0.004~0.01 and wear rate of 4.7 × 10-7 mm3/N·m in an ultrahigh vacuum. Both the enhanced hardness by N-doping and sustainable formed MoS2 tribofilm contributed to the improved tribological property of MoSN/MoS2 multilayer film.