Research On Preparation And Performance Of Tin Bronze-graphite-MoS₂ Bearing Materials

Tin bronze is one of the preferred materials for preparing plain bearings.By adding solid lubricants such as graphite or MoS₂ to tin bronze,the friction performances of plain bearings can be effectively improved,leading to the expansion on the application scenarios.In this paper,the tin bronze-graphite-MoS₂ materials were prepared by powder metallurgy and the optimal sintering processes were explored.The influence of raw materials on the microstructures and properties was studied,and the influencing factors of the friction properties in the sliding friction processes were analyzed,which provided theoretical guidance for the applications of tin bronze-graphite-MoS₂ materials in different working conditions.The effects of sintering temperature,sintering time and sintering method on the properties and microstructures of tin bronze-graphite-MoS₂materials were studied.The optimal sintering process was determined.Results show that the bronze-graphite-MoS₂ material had the highest vickers hardness,density and compression strength when sintered at 780℃for 2 hours under hot isostatic pressing.In this situation,the pores in the material were least and smallest,and the microstructures became much more uniform.The effects of raw materials on the microstructures and properties of tin bronze-graphite-MoS₂ materials were studied.Results show that the sample sintered with Cu-Sn pre-alloyed powders had higher vickers hardness and crushing strength,as well as denser microstructures.Copper coating on MoS₂ surfaces could improve the bonding properties between MoS₂ particles and the tin bronze matrix,which reduced the number and size of pores in the matrix and improved the density,vickers hardness and crushing strength of the tin bronze-graphite-MoS₂ material.The effects of copper coating on MoS₂surfaces and friction loads on the tribological properties and microstructures of tin bronze-graphite-MoS₂materials were studied.Results show that copper coating on MoS₂ surfaces could change the lubricating film’s morphology and thus optimized the material’s friction performance.Under the light load and heavy load conditions,the wear rate of copper coated samples was one order of magnitude lower than that of non-coated samples.Meanwhile,the friction coefficient decreased by 21.14%and 15.19%,respectively.Changes in frictional loads also had a significant effect on the friction properties of the material.With the increase of friction loads,the fluctuation of the friction coefficient curves decreased and the average friction coefficient of the material decreased either.The wear rate showed a trend of increasing first and then decreasing and reached its peak value under the load of 6N.At this time,the wear was mainly adhesive wear,oxidation wear and abrasive wear,accompanied by fatigue wear.When the load continued to increase,the material’s wear rates decreased slowly.In this situation,the material was mainly abrasive wear,accompanied by slight adhesive wear.