| 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,while its understanding is not enough presently.In addition,conventional friction device can not evaluate such a complex process.In this paper,we explore the preparation of Au thin films by magnetron sputtering.The effects of different negative bias and doping of different elements on the structure and mechanical properties of Au films were studied.The evaluation conditions for friction and wear of vacuum current-carrying are established.The influence of structure and mechanical properties on thin films of the friction properties with vacuum current-carrying has also been studied.Finally,the tribological behavior and mechanism of traditional electroplating gold are studied too.Furthermore,the difference between magnetron sputtering Au thin film and traditional electroplating gold coating is compared.The main results of this thesis are as follows:(1)The Au films under different negative bias voltage were prepared by magnetron sputtering,where the sputtering current is 0.2A.It is found that with the increase of negative bias pressure,the grain size changes from long strip distribution to granular shape,the roughness decreases first and then increases,and the mechanical properties are obviously improved.At the negative bias voltage of 100 V,the friction coefficient is low,the fluctuation of contact current and contact voltage is small and the wear rate is low.It has excellent friction performance.(2)Au films doped with different elements(Cu、Ni)were prepared by magnetron sputtering.After doping a small amount of Ni elements,the preferred orientation of the crystal plane of the thin film(111)is improved.It is found that the grain size is small,the roughness is low,the friction coefficient is low,the electric noise signal is low,and the friction performance of vacuum current-carrying is excellent.(3)The influence of load and current on the tribological properties of electroplated gold coatings under vacuum current-carrying is studied.It is found that the noise fluctuation of the contact current becomes larger,the contact tends to be more unstable with the increase of the current under the fixed load.At the same time,the wear rate increases.For small current,it is mainly adhesive wear and abrasive wear,while the arc erosion occurs when the current is large,which cause electrical wear.At the fixed current,with the increase of load,the contact current tends to be stable.The wear rate decreases,and the wear failure occurs when the load is too large.Wear mechanism changes from electrical wear to mechanical wear with increasing load.(4)Compared with electroplating,the gold film prepared by magnetron sputtering shows obvious smooth and compact structural characteristics.Moreover,it also show that its conductivity,hardness,vacuum current carrying wear rate and contact current noise are greatly improved. |
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