Corrosion And Wear Behavior Of Cu-WS₂ Composites In Marine Environment

Joint bearings or parts served in the marine environment need to add lubricating oil and grease to achieve lubrication.The traditional lubricating oils and greases are prone to drip and volatilization during application,leading lubrication failure and environmental contamination.Solid self-lubricating composite provides a built-in lubricant during sliding.It forms a lubricating film on the contact surface,thereby achieving long-term effective lubrication.Copper-matix self-lubricating composite is widely used in equipment manufacturing,electron technology,aerospace and many other fields,due to their excellent electrical conductivity,hot workability and corrosion resistance.Therefore,it has attracted attention of most scholars.In this paper,copper matrix self-lubricating composites were prepared by spark plasma sintering(SPS)technology in different sintering processes,which set Cu as the matrix,and WS2 as the lubricating phase.The phase composition,microstructure,and morphology of material were analyzed by XRD,SEM and TEM.Friction and wear performance and tribocorrosion of composite were tested by MFT-5000 friction and wear tester.Main research contents are listed as follows.Two kinds of composites containing Cu-10 wt%WS2(C10W)and Cu-20 wt%WS2(C20W),were successfully prepared by sintering at 850?.Corrosion behavior of composite in neutral salt spray environment was investigated,for analyzing the corrosion mechanism of composite and its effect on tribological properties.Some conclusions are drawn:C10W and C20W have suffered severe pitting in salt-fog environment.Compared with C20W,C10W has higher corrosion rate and more pitting pits.However,their corrosion process can be summarized into three stages:electrochemical corrosion—oxide film growth—electrochemical corrosion.There is a small difference between C10W and C20W of friction coefficient under dry friction after 3 days of corrosion.Wear mechanism of Cu-WS2 composite under dry friction is mainly adhesive wear.After salt spray corrosion,the wear mechanism is changed to abrasive wear.After three days of corrosion,the wear rate of C10W reached 5.24×107 mm3/(N·m),while of C20W was only 0.07×10-7 mm3/(N·m).In addition,wear rates of the two kinds of composite showed different trends with the increase of corrosion time.The wear rate of C10W increases gradually as the corrosion time increases,while of C20W decreases as the corrosion time increases.In first experiment,the composite Cu-20 wt%WS2 showed better performance,so this component was seleced for the next experiment.In order to improve lubrication property of Cu-20 wt%WS2,reduced the sintering temperature to 800?(the composite denoted as C20W-800?).C20W-800? and alloy QAl10-3-1.5(denoted as QAL)were subjected to artificial seawater immersion experiments and tribocorrosion experiments.Results show that corrosion behavior of QAL is greatly affected by friction and wear,due to depassivation/repassivation.Corrosion potential of QAL changed from-0.29 V to-0.79 V before and after friction,and the corrosion current density increased by two orders of magnitude.However,the corrosion behavior of C20W-800? was almost unaffected by friction behavior.Under constant potential polarization of+0.5 V,lubrication performance of the two kinds of materials was optimal.Friction coefficient of C20W-800? is as low as 0.15,while of QAL is about 0.26.The lubrication performance of C20W-800? promoted whether anode voltage or cathode voltage is applied.However,the lubrication performance of QAL was improved only at anode potential.