Controlled Deposition And Tribological Properties Of MoS₂ Based Composite Films By Magnetron Sputtering

Used magnetron sputtering technology,Mo S₂/a-C:H composite films with different carbon contents were prepared by adjusting the ratio of Ar/CH₄ flow rate,and MoS₂/Al composite film with different Al contents were prepared by adjusting the sputtering current of Al target.The surface and fracture morphologies of MoS₂/a-C:H composite films and MoS₂/Al composite films were characterized by scanning electron microscopy（SEM）and transmission electron microscopy（HRTEM）.The crystal structure and composition of MoS₂/a-C:H composite films and MoS₂/Al composite films were investigated by X-ray electron diffraction（XPS）and X-ray electron energy.The hardness and elastic modulus of MoS₂/a-C:H composite films and Mo S₂/Al composite films were characterized by nanoindentation tester.We investigated the tribological behavior of MoS₂/a-C:H composite films and Al₂O₃ ball with MoS₂ and bare Al₂O₃ ball.At 25℃,150℃,250℃,350℃,450℃conditions,high-temperature tribological behavior of MoS₂/Al composite films were investigated.The research in this paper shows that,molybdenum disulfide target and graphite target were co-sputtered with magnetron sputtering equipment,and high quality films with different Ar/CH₄ flow ratios were obtained.At the same time,the Mo S₂ layer was successfully deposited on the surface of Al₂O₃ ball（φ=6mm）and acted as a friction pair.MoS₂/a-C:H composite films with different carbon contents can be obtained by adjusting the flow ratio of Ar and CH₄.The carbon content increases gradually,the hardness of the composite films increase from 6.17Gpa to 19.36Gpa,the elastic modulus increase from 57.66Gpa to123.28Gpa,the hardness and elastic modulus increasing which is the key to the ultra-low coefficient of friction and long lubrication life of the Mo S₂/a-C:H composite films.MoS₂/a-C:H composite films with Ar/CH₄=80/30 were prepared by adjusting the ratio of Ar and CH₄.The tribological properties were the best among the series of films.The friction coefficient was as low as 0.0059 and the wear rate was as low as 3.4×10^-7mm³/N·m.Compared with pure Mo S₂ film,the friction coefficient is reduced by 86.83%.At the same time,compared with the friction coefficient of MoS₂/a-C:H composite film and MoS₂ coated Al₂O₃ and bare Al₂O₃ ball,the friction coefficient between the film and the Al₂O₃ naked sphere pair,the MoS₂ layer prepared on the surface of Al₂O₃ ball can significantly reduce the friction coefficient,prolong the lubrication life and make the lubrication process smooth.However,the tribological properties of MoS₂/a-C:H composite films under high temperature condition,it is found that the lubricating properties of MoS₂/a-C:H composite films drop sharply until they lose its lubricity.This is mainly due to the increased graphitization of a-C:H under high-temperature conditions,reduced bearing capacity,destruction of the MoS₂ structure,and resulting in loss of lubricating properties.Therefore,the MoS₂/Al composite film was prepared which shows excellent lubricating properties at high temperature.The study demonstrate that MoS₂/Al composite film prepared by magnetron sputtering own a nice structure.The introduction of appropriate content of Al did not cause a significant change in the structure of MoS₂,but as the Al content further increased,the structure of Mo S₂change dense and the mechanical properties increased rapidly.By co-sputtering Mo S₂ target and Al target,Al element can be doped into MoS₂ effectively,and Al content can be controlled by adjusting Al target current.When the content of Al in the composite film is appropriate,the introduction of Al plays an important role in its own oxidation without destroying the Mo S₂structure,and protecting the MoS₂ structure from being destroyed by the high temperature environment.When the temperature is 450℃,MoS₂/Al composite film with Al content of18.3%exhibits excellent lubrication performance at high temperature.The friction coefficient at the initial stage is maintained at about 0.07,and the average friction coefficient is as low as0.172,the coefficient is reduced 64%.Therefore,Al doping enhances the lubrication performance of Mo S₂ thin film at high temperature.The optimum addition amount of Al should be 18.3%.