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

本课题组介绍了一种新的超高真空润滑方法--原位摩擦涂层，并从摩擦系数的角度说明了原位摩擦涂层作为一种实用固体润滑方法的有效性。该方法是在真空中摩擦过程中，在接触界面上通过短时间沉积形成润滑剂薄膜。该方法具有涂层可按需修复的独特优点，可实现摩擦元件的无限寿命，本研究的最终目的是开发一种由摩擦涂层提供润滑膜的自修复系统。为实现空间机构润滑油的自恢复系统，本研究的两个关键问题是：1.研制了小尺寸（<1 mm）、低功耗（< 1 W）的微蒸发源（MES），用于原位摩擦涂覆，2.摩擦磨损低摩擦机理分析本研究的主要结果如下：1.研制了世界上最小的铟蒸发源。用研制的MES蒸发固体润滑剂（铟）所需的功率为560 mW.2.用研制的MES摩擦涂层的球轴承获得了足够低的实际使用的摩擦系数为0.005（500μmx500μm）。3.在销上形成的摩擦涂层具有纳米有序复合结构，纳米尺寸的铟分布在氧化硅和氧化铬的基体中。4.由分布的纳米尺寸的铟形成非常薄的铟膜，而不像常规的预涂薄膜那样破裂。较薄的铟膜可以提供比常规固体润滑剂更小的摩擦系数值。

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.