Study On Preparation And Friction And Wear Properties Of Copper-based Graphite Self-lubricating Bearings

Copper-based graphite self-lubricating bearings can self-lubricate under harsh working conditions such as high temperature,low temperature,pollution,corrosion,fresh water or seawater,vacuum,and radiation,and have unparalleled advantages such as low friction coefficient,small wear and long life.The content of graphite and its distribution in the copper matrix and the interface state of the two directly affect the overall performance of self-lubricating bearings.The traditional methods of preparation are mainly powder metallurgy and metal damascene,and how to achieve the content of graphite and its distribution in copper controllable in the matrix is still a technical problem.In this paper,3D printing technology is introduced into the preparation of copper-based graphite self-lubricating bearings.The three-dimensional graphite skeleton is pre-designed and then combined with copper alloy to achieve the above goals,so as to obtain copper-based graphite self-lubricating with excellent overall performance.Bearings to meet the needs of certain occasions.According to the self-lubricating friction and wear mechanism,a staggered distribution of graphite skeleton structure was designed.The mechanism and process of selective laser sintering were experimentally studied.The optimum process parameters were determined to ensure the molding processability of graphite/phenolic resin mixed powder and graphite forming.The accuracy of the parts,study the post-processing process of graphite moldings.The results show that when the laser power is 28W,the scanning speed is 1500 mm·s^-1,the scanning pitch is 0.12mm,and the layer thickness is 0.10mm,the relative errors in the X and Y directions can be controlled within 2%.The graphite flexural strength of graphite molded parts can reach 2.60 MPa.Through the secondary curing,vacuum pressure impregnation of phenolic resin silica sol,carbonization and high temperature sintering process,the graphite skeleton flexural strength was successfully upgraded to 27.11MPa,fully meet the requirements of use.The copper electroplating process on the surface of graphite skeleton and the extrusion casting process of graphite skeleton and tin bronze alloy were studied experimentally.The research shows that when adopting the following electroplating copper process parameter combination（the bath temperature is 30°C,the plating time is 30minutes,the Cu SO₄·5H2O concentration is 80g/L,the H₂SO₄ concentration is 2000g/L,the current density is 0.64A/dm²,and the stirring interval is 10min）Can get the maximum deposition rate.Studies have shown that the electroplating of copper on the surface of the graphite skeleton can completely guarantee the interface bonding between the two.When the temperature was 900°C,the extrusion force was 10MPa,and the holding time was 0.5h,the tin bronze-graphite self-lubricating bearing specimen was successfully prepared by squeeze casting.The friction and wear properties of copper-graphite self-lubricating bearing samples before and after copper plating,graphite content and graphite skeleton structure were experimentally studied.The results show that the friction coefficient and the wear of the obtained samples are lower after the copper plating on the surface;the friction coefficient of the composite sample decreases with the increase of the graphite content,and the wear amount first decreases and then increases.For the trend,30%of the graphite content has a lower friction coefficient and the smallest amount of wear;while the friction and wear of the two sets of samples with the same graphite content are different.