Tribological Characteristic Evaluation of Tungsten Disulfide Solid Lubrication Films

To be used in severe outer space environments, spacecraft may also cause unexpected problems from the ground level. In order to solve the problems, it is important that many of the sliding portions of the spacecraft have been prepared by the lubrication processing. A solid lubricant is suitable in the space environment such as a low pressure and wide temperature changes. Gold film and molybdenum disulfide have been mainly utilized for solid lubricant in spacecraft. These materials have been already examined the tribological characteristics using the variety of additives. Although these lubricants have been applied in the various space environments, tungsten disulfide which has the same crystal structure as molybdenum disulfide has not been studied intensively. In this study, tungsten disulfide has been examined for the application of the solid lubricant in the spacecraft. In order to simulate the deployment friction, the reciprocating tribometer experiments were conducted in a vacuum and air using the aluminum alloy and the stainless steel substrates coated by tungsten disulfide. It was found that the tungsten disulfide lubricant coating have demonstrated the lowest friction coefficient among other solid lubricants. But it also reached its wear life before the end of test duration in a vacuum. To improve the wear life of tungsten disulfide, substrates which coated by mixture of tungsten disulfide powder and polyamideimide have been studied. Comparisons of the two coating methods have been elucidated in conjunction with wear morphology observed by EDS-SEM.