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

本课课组介绍了一种新的超高真空下的原位摩擦涂层润滑方法，从摩擦系数的角度清楚地显示了其作为实用固体润滑方法的有效性。该方法在真空摩擦过程中，通过在接触界面上的短时间沉积形成一层薄膜润滑剂。该方法具有镀层可按需修复的独特优势，并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的润滑膜的自修复系统。为实现空间机构的润滑自修复系统，本课题重点研究以下两个问题：1.润滑自修复系统；小尺寸（< 1mm）、低功耗（< 1w）微蒸发源（MES）的研制；本文研究的主要成果是对铟摩擦涂层的低摩擦机理进行了分析。研制出世界上最小的铟蒸发源。使用开发的MES蒸发固体润滑剂（铟）所需的功率为560 mw。采用所研制的MES（500μmx500μm）涂覆tribo涂层的滚珠轴承摩擦系数低至0.005，符合实际使用要求。3 .在引脚上形成的摩擦涂膜具有纳米级复合结构，其中纳米尺寸的铟分布在氧化硅和氧化铬基体中。与传统的预涂薄膜一样，由分布的纳米级铟不分解而形成极薄的铟薄膜。与传统固体润滑剂相比，较薄的铟膜可以使摩擦系数更小。

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.