真空环境下类富勒烯碳薄膜与不同配副材料的摩擦学性能

Tribological Behavior of Fullerene-like Carbon Films Against Various Mating Materials in Vacuum Conditions

目的提高类富勒烯碳薄膜真空摩擦学性能。方法采用等离子增强化学气相沉积技术(PECVD)制备了类富勒烯碳薄膜(FLC),利用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、拉曼光谱(Raman)和纳米力学仪等研究了薄膜厚度、结构及力学性能。采用真空摩擦试验机考察了真空环境下类富勒烯碳薄膜分别与非晶碳薄膜(DLC)、FLC、钢球和MoS_(2)薄膜组成配副的摩擦学性能,结合磨痕形貌和转移膜Raman及HRTEM结构分析,探究了材料的摩擦磨损机制。结果MoS_(2)与FLC组成的摩擦副具有低摩擦因数(0.02)和低磨损率(10‒20 m^(3)/(N·m)),类富勒烯碳薄膜具有高硬度,能够在摩擦过程中支撑容易“坍塌”的MoS_(2)。结论在摩擦过程中类富勒烯结构因剪切力和Mo的催化作用发生解构现象,引起薄膜中的sp3向sp2转变,并且重建为片状石墨片。MoS_(2)形成了转移膜在摩擦过程中扮演的角色一方面是润滑剂,另一方面是催化剂,作为润滑剂能够改善磨损情况,作为催化剂参与类富勒烯结构的重构过程,获得在真空环境下的低摩擦因数和低磨损性能。

Lubrication failure of space moving parts has become a bottleneck restricting the service life and reliability of space technology equipment.At present,aerospace solid lubrication materials used in aerospace equipment are mainly disulfide layered structure compounds,such as molybdenum disulfide,which has a layered hexagonal crystal structure and is a thin layer unit composed of three planar S-Mo-S layers.However,due to the weak interlayer structure,molybdenum disulfide is likely to wear under high loads,so it can not meet the requirements of system durability under high loads in space.Fullerene-like carbon films(FLC)with high hardness and excellent elastic recovery coefficient achieve ultra-low friction(0.008)in atmospheric environments.Fullerene-like carbon films are expected to be widely used as a new type of space solid lubrication films,but the tribological properties of fullerene-like carbon films with various pairs under vacuum are rarely studied.In this paper,fullerene-like carbon films were prepared by plasma enhanced chemical vapor deposition(PECVD).The thickness,structure and mechanical properties of FLC films were studied by scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),Raman spectroscopy and nanomechanics.The tribological properties of fullerene-like carbon films with amorphous carbon films(DLC),FLC,steel balls(440C)and MoS_(2) films were investigated by vacuum friction testing machine.Combined with the wear morphology and the Raman and HRTEM structure analysis of transfer films,the friction and wear mechanism of the materials were investigated.The results showed that the friction curves of FLC/DLC friction pairs varied greatly.Although FLC/DLC friction pairs could achieve a lower friction coefficient(0.02),the friction life was short and friction failure occurred quickly.Since FLC or DLC deposited on the surface of 440C was deposited by PECVD,the carbon film deposited on the metal surface usually needed to deposit the transition layer first to enhance the binding force.Because we could not deposit the transition layer by vapor deposition,the binding force was limited,and the DLC ball/FLC ball was likely to fall off during the friction process,and the friction performance of the carbon film was limited in vacuum.Because the friction heat generated in the process of friction could not be transferred in time in the vacuum environment,the accumulation of friction heat led to local temperature rise,which led to dehydrogenation.The vacuum friction of carbon film depended on the hydrogen content of the film,and the reduction of hydrogen content led to friction failure.Although there was no failure problem between the 440C steel ball and FLC,the friction coefficient was relatively large,and only the friction coefficient obtained by MoS_(2) and FLC was low(0.02),and there was no failure.MoS_(2)/FLC showed the lowest wear rate(1.16×10‒20 m3/(N·m)).Although the friction coefficient of MoS_(2)/MoS_(2) in vacuum was stable,its wear rate was high,the hardness of MoS_(2) film was low,and it was likely to"collapse"during the friction process,so its wear rate was relatively large.The friction pair composed of MoS_(2) and FLC had a low friction coefficient(0.02)and a low wear rate(10‒20 m3/(N·m)),and the fullerene-like carbon film had a high hardness,which could support MoS_(2) that was likely to"collapse"during the friction process.The main reason is that the fullerene-like structure deconstructs due to the shear force and the catalytic action of Mo during the friction process,which causes the transformation of sp3 to sp2 in the film and the reconstruction into flake graphite.MoS_(2) forms a transfer film in the friction process and plays the role of a lubricant on the one hand,and a catalyst on the other hand.As a lubricant,it can improve the wear situation;and as a catalyst,it participates in the reconstruction process of fullerene-like structure,to obtain low friction coefficient and low wear performance in a vacuum environment.