| Bump-foil bearings has a broad application prospect in high-speed rotating machinery because of its excellent performance,but its service life is seriously affected by the friction and wear in start and stop stage.Therefore,the solid self-lubricating coatings on surface of top foil and journal was studied experimentally in this paper.Based on the analysis of film formation and adhesion mechanism,the compositions of coating was designed according to the friction and wear characteristics of top foil,a low temperature cured and high temperature resistant coating was prepared by air gun method.In order to optimize the ratio of compositions,The optimum curing temperature and content of curing agent were determined by orthogonal experiment.Through the comprehensive performance test of coating with different formulations,it was found that adding mullite fiber was beneficial to enhance the toughness and bonding strength.When the content of metal filler was 70%,the surface quality and hardness of coating were the best and average friction coefficient was only 0.27,phosphate coating has an excellent wear and friction reduction performance.In the experiments of pin disk friction and wear with different variables of heat treatment temperature,load and rotation speed,the coating's friction coefficient was kept in the range of 0.3?0.5from room temperature to 500?.lower load will affect the stability during the wear process,while higher load will increase wear amount.With the increase of rotating speed,the friction coefficient and wear amount increased at first,then decreased.and the wear pattern of coating mainly showed abrasive wear.In order to explore the effect of friction reduction and wear resistance of hard film in bump-foil bearings,TiN/Ti coating was prepared on the surface of GCr15 journal by vacuum multi arc ion plating.The results show that the coating has good surface quality and high bonding strength with substrate,and the average friction coefficient is only 0.23.Through the performance test by bench test device,compared with the uncoated journal,It is found that the maximum friction moment of TiN/Ti coated journal is dropped significantly,the wear resistance is good,and the stability is greatly improved in start-stop process,which fully shows that the coating has good lubrication performance,load-bearing capacity and excellent wear-resistant and antifriction performance. |
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