Nanocrystalline/Amorphous Tantalum-Silver Structure Regulation And Tribology Performance Research

Based on the extremely harsh conditions of high/low temperature?wide temperature range?,special medium and high speed,etc,commonly exist in the high-tech industries such as modern aviation,aerospace,transportation and electric power,self-lubricating protective coatings with stable structure under high temperature conditions becomes more and more urgent.Tantalum can be used as a potential anti-ablation protective coating due to its high melting point,chemical inertness and high corrosion resistance,while Ag,as an excellent low and medium temperature lubrication component,has been combined with other solid lubricants to achieve wide-temperature lubrication.In this paper,DC magnetron sputtering was used to deposit tantalum-silver coatings on the surface of steel.The optimization doping elements was Ag,and the sputtering parameters like powers and pressures were adjusted to control the coating grain size and crystal structure.The tribological properties of the coating from room temperature to 750°C were tested.Aiming at the key problems of controllable release of lubricant and self-adaptation of friction surface lubrication in the design of anti-friction and anti-wear coating with wide temperature range.We focused on the formation process and structural evolution of the friction interface in thermal,mechanical and chemical coupling as well as the cluster segregation phenomenon under the action of heat and force including its effects on microscopic and macroscopic friction mechanisms.Through the relationship between process,structure and performance,the experimental method was used to examine the performance and service behavior of nanocrystalline tantalum series coating for optimize the design of coating structure components.The preparation of nanocrystalline?-Ta was achieved by controlling the sputtering powers and pressures,the crystallization power of Ta-Ag film is 90W and the microhardness of nanocrystalline Ta is 12-13GPa,the crystallization power of Ta film is above 110W.It suggested that the addition of Ag as a heterogeneous nucleation point promotes the crystallization process.The working pressure affect the phase structure of Ta,and the high-pressure film had a clear amorphous tendency.The wear rate of the 0.2-0.4Pa crystallized film after 700°C is as low as16.5×10^-6mm³/Nm;The heat resistance of the coating are improved after the addition of appropriate amount of alloy elements.The addition amount of Ag is higher than 10%,the hardness of alloy film decreases linearly,and the composite state of Ag cluster and Ta₂O₅ exists at the friction interface of 700°C.The synergistic lubrication effect of these two phases can keep the friction coefficient stable below 0.40.When the Ag content is 11.5%,the wear rate is as low as 19.3×10^-6mm³/Nm;The addition of the transition layer Nb/TiN can significantly improve the film performance and the nanocrystalline Ta-Ag film with Ag content less than15%has a microhardness of 12-16GPa.The heat resistance can be increased to 750?in the addition of transition layer.The binary metal oxide is formed in the wear region and the corresponding friction coefficient is stabilized between 0.20-0.35.The films still maintain the nanocrystalline structure after high temperature experiment.