Development of Self-restoring Ball Bearing for Space Application by Tribo-coating

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A new lubrication method in ultra high vacuum called as in-situ tribo-coating was introduced by our group, and its effectiveness as practical solid lubrication method was clearly shown from the viewpoint of friction coefficient. In this method a thin film of lubricant is formed by short time deposition on a contact interface during the process of friction in vacuum. This method gives unique advantage that the coating can be restored on demand, and endless life of the tribo-element can be achieved.The ultimate objective of this research is to develop a self-restoration system of lubricant film supplied by the tribo-coating. Following are two key subject in this research to realize the self-restoration system of lubricant for the space mechanisms ;1.Development of Micro Evaporation Source (MES) with small size (<1 mm),and low power consumption (< 1 W) for the in-situ tribo-coating,2.Analysis of low friction mechanisms of tribo-coatings of indiumFollowing are main results of this research.1.The world smallest evaporation source for indium was developed. The power needed for evaporation of the solid lubricant (indium) with the developed MES was 560 mW.2.Sufficiently low for practical use friction coefficient of 0.005 was obtained with ball bearing coated by Tribo-coating with the developed MES(500μmx500μm).3.The tribo-coating film formed on the pin has nano-order composite structure in which the indium of nano size is distributed in matrix of silicon oxide and chromium oxide.4.A very thin indium film is formed by the distributed nano-size indium without break down like conventional pre-coated thin film. The thinner indium film can give smaller value of friction coefficient than that of conventional solid lubricant.