Study On The Mechanics Of Lead-free Copper-bismuth Sliding Bearing Materials And Friction And Wear Characteristics

Lead is a toxic and harmful elements, lead-free products is imperative with thedevelopment trend of environmental protection, The non-toxic low melting pointelement bismuth is used as a soft phase and graphite as a solid lubricant in thispaper，we expect that the lead can be replaced by the synergy of the anti-frictiongraphite and anti-adhesion bismuth, to achieve lead-free copper bearing materials.Lead-free copper-bismuth, copper-bismuth contained graphite bearing materialswere prepared by the conventional powder metallurgy method. Study on theMechanics and the tribological properties were conducted under differentconditions. In order to investigate the friction and wear mechanism of lead-freecopper bismuth bearing, microstructure, fracture and worn surface morphology andsurface profile, the chemical composition of the worn surface are analyzed withscanning electron microscopy, optical microscopy, surface morphology profiler andother means of microscopic analysis.The study showed that the bismuth content have a greater impact on themechanical properties of lead-free copper-bismuth bearing materials. Thecontinuity of copper alloy matrix was destroyed with the increase of Bi elementbecause of Bi is brittle phase and distributed in the copper alloy matrix grainboundaries as thin ribbon network. The hardness and crushing strength and impacttoughness of copper-bearing materials were reduced with increase of the content ofBi. The mainly of Copper-bearing materials containing bismuth fracture are brittleintergranular fracture. Shape of Bi-rich phase is more complete when the Bi contentis more than4wt%, and the reduced trends of the mechanical properties ofCopper-bearing materials containing bismuth were relaxed because the role offragmented Copper alloy matrix will not significantly increase with further increaseof Bi.The low melting point element bismuth in Copper-bismuth sliding bearingmaterials melting and precipitating to direct contact region of friction surfacebecause of frictional heat, it can help reducing shear strength of the contact area,stabling friction pairs. The content of bismuth has greater impact on thetribological properties. Suitable bismuth content can improve their anti-friction, wear-resistant, and anti-adhesion performance. Add the appropriate content ofgraphite can be further improved anti-friction bearing material of lead-free copperbismuth, anti-adhesion performance, and improve the wear resistance. Copperbismuth anti-friction bearing material with copper graphite or nickel-platedgraphite has better anti-friction and anti-adhesive characteristics because of coppergraphite and nickel-plated graphite combined with copper alloy matrix better.Bismuth and graphite has better synergy in anti-friction, anti-adhesion.