Design And Tribology Study Of Self-lubricating Coating On Plain Bearing At Different Temperature

The boundary lubrication and even dry friction of plain bearings at different work temperature are unable to be avoided under the start and stop condition.The poor lubrication is one reason of bearing broken.In order to improve the performance of bearings at different temperature,the common method is the self-lubrication coating to decrease the high Co F(Coefficient of friction).The shortages of bonding fiber woven materials,inlaying solid lubricating materials,electro plating and magnetron sputtering are poor temperature resistance,low load capacity,environment pollution and low production efficiencies respectively.The best way is the spraying technology to deposit the room temperature,middle and high temperature self-lubrication coating.However,the technologies,the theories and self-lubrication materials should be studied deeply.This research is supported by China marine low speed engine project of phase 1and China aerospace science and technology innovation fund.The self-lubrication coatings work at room temperature,middle and high temperature which are designed for the plain bearings at room temperature,200?and 800?.The mechanisms of laminar flow and leveling of coating are studied through the new designed automatic spraying machine.The best parameter ranges of spraying are determined by the studies of sagging coating,leveling coating,the best coating thickness,the best roughness of substrate,the best curing temperature,the best cooling temperature and so on.Mo S₂ powders are used as self-lubricating material.Resin and polyimide are used as adhesion materials.They are mixed as a special ratio to form the Mo S₂ based lubricating dope.The Co Fs(coefficients of friction)of Mo S₂ coating made from its dope at room temperature and 200?are 0.12 and 0.09 respectively.The hardness of coating is 29.18 HV.The adhesion of coating and substrate is excellent,and there is no obviously porosity.The fatigue cycle life of bearing is multiplied improved.To satisfy the different work conditions and avoid the single material overusing,and take the cost into consideration,the PTFE based dope is designed to satisfy the lubrication at room temperature.Through the analysis of lubrication and physical properties,the results show that the Co Fs of the PTFE are 0.14 and 0.11 at room temperature and 200?respectively.The hardness of coating is 30.61 HV.Comparing with Mo S₂coating,the Co F is lower and its anti-wear is better with the different resin and the additive anti-wear materials.The properties of two designed coating dopes are better than that of the dopes made from overseas.The h-BN based dope and WS₂ based dope are designed for the 200?work condition,and the modified resin and polyimide materials are used which are able to be served for long time.The ratio of solid lubricating materials and anti-wear added materials are optimized,that lowest of the WS₂ coating is 0.05,and that is 0.07 of the h-BN coating.The results show that the properties of plain bearings are improved greatly through the experiments of adhesion,porosity,equivalent stress and fatigue cycle life.Plain bearings with dope and liners treatments would lose the lubrication quickly at high temperature of 800?.The best parameters of solid powders spraying are determined by the performances and the optimization thickness of soft and hard alternated coatings.A MAX-phase coating is formed on the surface of high temperature resistant alloy steel through the supersonic flame spraying.The results show that the Ti₂Al C coating has the lubricating performances at room temperature and 800?.The C/C composites are used as the bearing substrate due to the excellent properties.The Si C coating is formed by the sintering packing method.The VN coating is formed by spraying.The Mo S₂ and Ta are mixed together,and the different mixed proportions are designed.They are sprayed as the Mo S₂/Ta coating with the best mixed proportion.The Co Fs are 0.28 and 0.16 at room temperature and 800?respectively from the frictional experiments.The oxidation loss is decreased also.The self-lubricating coatings are developed for the low,middle and high temperature wok condition of plain bearings,and the best applications are suggested by the comparisons of different coatings.The new designed coatings satisfy the self-lubricating requirement at wide range temperature through the frictional experiment,porosity and adhesion tests,equivalent and fatigue cycle life experiments.The Co Fs and max equivalent stress are decreased,and the lowest fatigue cycle life is improved with the new designed self-lubricating coatings.