Research On High Temperature Lubrication Properties Of Co-sulfate Composites

Cobalt-based self-lubricating composite materials have broad application prospects in the aviation field.However,traditional cobalt-based materials have disadvantages such as low operating temperature,poor dimensional stability,and incompatibility between mechanical strength and self-lubricating performance.Therefore,it is urgent to develop a new type of cobalt-based self-lubricating composite material.In this paper,the cobalt-based self-lubricating composites with high-temperature lubricants with different sulfates were prepared by hot pressing sintering technology.The effects of sulfate on the tribological properties of cobalt-based self-lubricating composites at room temperature to 1000°C and friction mechanism were studied.The high temperature wear models of cobalt-based self-lubricating composites with different sulfates were established and studied.As lubricants,BaSO₄ and SrSO₄ can significantly improve the high temperaturetribologicalpropertiesofcobalt-basedself-lubricating composites.BaSO₄ can make cobalt-based composites exhibit low friction coefficient and wear rate in the temperature range of 400⁸00°C,this is because the friction surfaces of cobalt-based self-lubricating composites containing BaSO₄ gradually form the lubricating film which is composed of CoO,Co₃O₄,Ba₃?CrO₄?₂ and CoMoO₄ as the temperature rises.SrSO₄ can make cobalt-based composites exhibit low friction coefficient in the temperature range of200¹000°C,this is because the friction surfaces of cobalt-based self-lubricating composites containing SrSO₄ gradually form the lubricating film which is composed of CoO,Cr₂O₃,WO₃,CoWO₄,CoMoO₃,SrSO₄ and Sr₃?CrO₃?₂ as the temperature rises.With the increase of temperature,the friction coefficient of cobalt-based self-lubricating composites containing BaSO₄ decreases firstly and then increases,the wear rate increases firstly,then decreases and then increases.The friction coefficient of cobalt-based self-lubricating composites containing SrSO₄ decreases firstly,then increases and then decreases,and the wear rate increases firstly,then decreases and then increases.The synergistic effect of BaSO₄ and SrSO₄ as lubricants also improves the tribological properties of cobalt-based self-lubricating composites.The hardness and density of three cobalt-based self-lubricating composites with different BaSO₄/SrSO₄ ratios are almost identical.With the increase of temperature,the friction coefficient of cobalt-based self-lubricating composites containing BaSO₄/SrSO₄ increases firstly and then decreases,and the wear rate increases firstly,then decreases and then increases.The cobalt-based self-lubricating composites with a mass ratio of BaSO₄ to SrSO₄ of 3:1 exhibit the best tribological properties in the range of 400-1000°C.The high temperature wear models of cobalt-based self-lubricating composites with different sulfates was studied.Based on the Archard wear model,assuming a temperature and wear coefficient as a function of temperature,the high temperature wear models of BaSO₄ and SrSO₄ cobalt-based self-lubricating composites with BaSO₄ and SrSO₄ were established using MATLAB.The established wear model was consistent with the actual wear.