Study On Controllable Preparation And The Tribological Properties Of Bimetallic Oxides

With the development of high-tech industry,such as aerospace,the demands for self-lubricating materials working at wide temperature range are becoming more and more urgent.However,there are no single lubricating materials been found to enable continuous lubrication in wide temperature range.It had been found that Ti and Cr elements in Inconel 718 diffused and reacted with oxygen to form lubricious substances at high temperature,but the contents of these elements in the alloy steel were very small.Therefore,firstly,the cyclic oxidation of alloy steel at high temperature was studied.And the diffusion mechanism of elements at high temperature was actively controlled.Then,Cr_xTi_yO_z,Zn_xTi_yO_z and Ag_xV_yO_z bimetallic oxide films were prepared on the surface of Inconel 718 superalloy by multi-arc ion plating and magnetron sputtering techniques.After that,the prepared films were annealed.The structure,mechanical properties and tribological properties of the three different films before and after annealed were systematically investigated to further expand the engineering application of oxide coatings and provide technical support for self-lubricating materials in wide temperature range.The main tasks are as follows:（1）Inconel 718 alloy steel was oxidized for four cycles.It was heated to1000°C insulation for 120 minutes and cooled inside the furnace to room temperature.The Ti and Cr elements in the alloy steel diffused,and the surface was covered with an oxide layer.Based on the effect of cyclic oxidation on the structure and properties of the alloy steel,it could be found that with the increase of the number of oxidation,the structure of the oxide film was transformed from a uniform dense rod-like structure into a loose honeycomb structure.The hardness of the alloy steel showed a gradual decline trend after several thermal cycles.There was no significant difference in friction coefficient of the alloy steel.However,the wear rate showed a gradual increased trend.（2）Since the contents of Ti and Cr in the alloy steel were relatively small,bimetallic oxide films with different contents of Cr and Ti were prepared by multi-arc ion plating by means of active control.And the prepared films were annealed at 1000°C.The correlation between the structure and properties before and after annealed was indepth studied.The results showed that with the decrease of Ti content,the mechanical properties of the as-deposited films increased.The as-deposited film with Cr_0.15Ti_0.85O_1.925.925 and CrTiO₃ phase had excellent tribological properties.After being annealed at the 1000°C,the elements in the substrate were diffused and the structure became loose.So,the mechanical properties were poor and the wear rate was an order of magnitude higher than that of the as-deposited films.The wear rate of the film which was composed of Cr₂Ti₄O₁₁ phase with no lubricity increased to 1.3×10^-5mm³/N?m.（3）The bimetallic oxide films with different contents of Zn and Ti were prepared by magnetron sputtering and the films were annealed at 600°C.The relationship between the structure and properties with different content of elements before and after annealed was comprehensively analyzed.It was found that with the decrease of Zn content,the number of the nuclear inside the film increased and the surface became denser.So,the hardness and bonding strength gradually increased.The friction coefficient and the wear rate of the film were0.154 and 7.4×10^-6mm³/N?m respectively,due to the formation of ZnTiO₃ and Zn O composite phases with lubricity on the surface.（4）The bimetallic oxide films with different contents of Ag and V were prepared by magnetron sputtering through adjusting the parameters of deposition process and the films were annealed at 700°C.The effects of different structures on the mechanical properties and tribological properties before and after annealed were analyzed.It could be seen that with the increase of the Ag/V in the film,the density of the film increased.The hardness and the bonding strength of the film gradually advanced,and the wear rate remained at the order of10^-4mm³/N?m.After being annealed at 700°C,the film which consisted of Ag₃VO₄,V₆O₁₃,and Ag₂O composite phases with lubricity had excellent tribological properties.