C2H2/Ar流量比对a-C:H涂层结构及摩擦学性能的影响

a-C:H涂层因具有高硬度、低摩擦系数及良好的化学惰性等性能，使其作为表面防护材料具有广泛的应用前景，而涂层中的H含量和sp2C/sp3C比值是影响其力学及摩擦学性能的重要因素. 本研究中采用非平衡磁控溅射技术在9Cr18钢表面制备了a-C:H涂层，对比研究了前驱体组成对不同结构含H碳膜的氢含量、微观结构、力学性能和摩擦学性能的影响. 结果表明:增大C₂H₂/Ar流量比，涂层的生长率及H含量逐渐增大，但致密性降低. 由于涂层中C-H键及致密性的变化，a-C:H涂层的硬度和弹性模量随C₂H₂/Ar流量比的增大而逐渐减小，但结合强度却先增大后降低. 当C₂H₂/Ar流量比低于4:3时，涂层表现出良好的减摩耐磨性能，当C₂H₂/Ar流量比高于4:3时，涂层的摩擦系数和磨损率出现了急增的现象. 总体而言，a-C:H涂层的摩擦系数和磨损率随C₂H₂/Ar流量比的增加呈现先增大后降低的趋势. 由于H原子的钝化作用及涂层力学性能的变化，使a-C:H涂层的磨损机制由磨粒磨损和黏着磨损变为磨粒磨损. 当C₂H₂/Ar流量比为1:1时，a-C:H涂层具有最低的摩擦系数(约为0.1)和磨损率8.0×10?8 mm3/(N·m)]，表现出最佳的力学及摩擦学性能，这种性能的变化与涂层中的H含量和sp2C/sp3C比密切相关. 

Effect of C2H2/Ar Flow Rate on Microstructure and Tribological Properties of a-C:H Coatings

a-C:H coatings have widely used as the surface protection material in different applications due to their high hardness, low friction coefficient and good chemical inertness, while the H content and sp2C/sp3C ratio in the a-C:H coatings are the key factors to affect the mechanical and tribological properties of the coatings. In this study, the a-C:H coatings were prepared on the surface of 9Cr18 steel substate via unbalanced magnetron sputtering technology, and the influences of precursor composition on the H content, microstructure, mechanical and tribological properties of the coatings were systematically studied. The results showed that the growth rate and H content of the a-C:H coatings monotonically increased as the increase of C₂H₂/Ar flow rate ratio, while the compactness decreased. The hardness and elastic modulus gradually decreased as a function of the C₂H₂/Ar flow rate ratio owing to the variation of the C-H bonds contents and compactness of the a-C:H coatings, but the adhesion strength between the substrates and coatings displayed a trend of first increased and then decreased. The coatings exhibited good friction and wear performances when the C₂H₂/Ar flow rate ratio was below 4:3, but the friction coefficient and wear rate of the coating significantly increased when the ratio was higher than the value. Overall, with the increase of the C₂H₂/Ar flow rate ratio, the friction coefficient and wear rate of the a-C:H coatings always decreased at first and then increased. Moreover, the main wear mechanisms of the a-C:H coatings were changed from the abrasive wear and adhesive wear to single abrasive wear as a result of the passivation effect of H atoms and changes of mechanical properties. In the case of C₂H₂/Ar flow rate ratio of 1:1, the a-C:H coatings had the lowest average friction coefficient and wear rate, and the values were 0.1 and 8.0×10-8 mm3/(N·m), respectively. This property superiority of the a-C:H coating was closely related to the H content and sp2C/sp3C ratio in the coating.