Research On The Super-lubrication Behavior Of Single Crystal Diamond Under Vacuum Environment

As one of the most potential materials in the field of super-lubrication,diamond material has a wide range of application prospects in reducing energy consumption and material wear,especially in prolonging the service life of mechanical parts in a space environment.In the extreme environment of space,the wear method of contacting materials is mainly adhesive wear.The traditional liquid lubrication and compound lubrication methods cannot meet the working requirements of modern aerospace mechanical friction systems.Therefore,we urgently need to develop a lubricant with long service life and reduced frictional wear.In a vacuum environment,the surface of the diamond material is prone to desorption,and air molecules and media are scarce in the working atmosphere,which limits the diffusion of the interface friction temperature.The above conditions make the diamond prone to cleavage and graphitization,making it possible for diamond to achieve self-lubrication in the vacuum environment.Based on the current research on the frictional properties of diamond materials,this project is intended to investigate the effects of different vacuum levels on the super-lubrication behavior of single crystal diamond and the influence of different ceramics on the super-lubrication behavior of single crystal diamonds through spatial friction and wear tests.Experimental results show that.（1）Single crystal diamond in atmospheric environment has high friction with a stability period of about 0.05,and its surface wear is caused by the polishing-like effect of abrasive chips.Compared with the atmospheric environment,single crystal diamond has more excellent tribological performance for grinding alumina ceramic material under vacuum environment.The test results show that the gradual increase of vacuum level in the cavity will lead to a gradual decrease of friction coefficient.At low vacuum level,single crystal diamond has high friction with a stabilization period of about 0.043,and at the same time,some of the grinding chips between the friction interface generate core-shell structure to achieve a lower friction coefficient.The friction coefficient decreases further with the generation of amorphous and laminated materials in the grinding chips at medium vacuum.At high vacuum degree the generation of laminated graphite in the grinding chips is accompanied,thus exhibiting super-lubrication,with a coefficient of friction of about 0.006 in the stable period.（2）The single crystal diamond superlubricity performance under high vacuum is influenced by the friction mating materials,in which Si₃N₄ and Zr O₂ exhibit low friction,with coefficients of friction of about 0.005 and 0.01,respectively,in the stable period,and interfacial grinding chips graphitize the diamond under mechanical action,and colored films appear on the grinding chip surface.For grinding Al N and SiC exhibit relatively high friction,the friction coefficients are about 0.02 and 0.056 respectively in the stable period,where frictional chemical bonding reaction occurs at the interface for grinding SiC material,accelerating the graphitization of single crystal diamond,and clear visible abrasion marks appear on the surface.（3）Single crystal diamond wears on the surface under the action of abrasive particles in both atmospheric and vacuum environments.The wear mode in atmospheric environment is dominated by mechanical deconstruction and graphitization,while the wear mode in vacuum environment is diamond low friction dominated by surface graphitization.