Preparation and Vacuum Current-Carrying Tribological Behavior of Au Film by Magnetron Sputtering

In the space equipment system, the sliding electrical contact parts are widely used, which plays an important role in the current switching, breaking, diversion and isolation of the circuit system. With the development of equipment and the increasing demands of the harsh application conditions, the service life and other properties of space conductive lubricating materials in service have shown obvious deficiencies. The reasons may be as follows. First, the gold-based conductive material (lubricating and coating) is mainly prepared by electroplating method at present. The film has some obvious weakness such as the coarse grain, the loose structure, the rough surface, the low mechanical properties and the insufficient life. Furthermore, the process of electroplating involves environmental pollution. Second, the service environment of space conductive lubricating materials is very complex and harsh. In addition to the conventional mechanical wear problems, it also involves the interactive coupling damage of high vacuum, arc and other factors. Moreover, the failure mechanism of friction and wear is very complicated, and its understanding is not enough presently. In addition, conventional friction device can not evaluate such a complex process. The establishment of vacuum current-carrying friction test conditions can completely simulate the real service conditions of space sliding electrical contact components, and it is very necessary for the study to reveal the friction and wear mechanism of space sliding electrical contact. A green magnetron sputtering method is used to prepare gold films in view of the shortcomings in the preparation method and the understanding of failure mechanism of space sliding electric contact gold-based lubricating coatings. The influence of bias voltage on films microstructure, mechanics and tribological properties of vacuum current-carrying was studied. The evaluation conditions of vacuum current-carrying friction test which can simulate the real service condition were established, and the real-time measurement of contact current noise was realized. The difference on friction and wear behavior, main influencing factors and mechanism of vacuum current-carrying friction and wear of Au films was prepared by magnetron sputtering and the traditional plating gold coatings was studied. The results showed that the Au film under moderate bias voltage had small grain size, dense and smooth surface structure, and shows high adhesion, hardness, wear resistance and low contact current noise. When the film grain size was smaller and the roughness was lower, the contact current fluctuation and contact voltage were smaller, and the wear rate was lower, which was attributed to the stable contact between the film and the pair. Compared with electroplating gold, the gold film prepared by magnetron sputtering showed smoother and more dense structure characteristics; in addition, the hardness, wear rate and contact current noise were greatly improved. Therefore, the smooth and dense structure were the key factor to suppress the micro arc, which can effectively reduce the arc erosion failure.