Investigation Of Preparation Process And Properties Of Silicon Carbide-aluminium Base Oil-impregnated Bearing

Aluminum basesintered oil-impregnated bearing has a broad space for research and developmentbecause of its better running-inability,light products,cheap,excellent thermal conductivity,etc.Silicon carbide?SiC?has been widely used in the field of reinforced composite materials with excellent mechanical properties.In the paper,the aluminum base sintered oil-impregnated bearing samples were prepared using powder metallurgy technology,and the copper coated silicon carbide particles?SiC?Cu??were prepared using electroless copper plating process.The influence and mechanism of SiC content,SiC?Cu?content and sintering temperature on the crushing strength,oil content and micro-morphology ofthe aluminum base sintered oil-impregnated bearingsamples were investigated.Electroless copper plating processcan be got a good plating Cu coating on the SiC surface in this paper.Electroless copper plating process included pretreatment and electroless plating.The pretreatment process includedethanol degreased,hydrochloric acid acidated,stannous chloride solution sensitized,silvernitrate solution activated.In the electroless plating process,the pH value of the plating solution was 12¹3,the temperature was 35?and plating time was 20min.By contrasted thedifferent plating effect of different addition amount of copper salt,reducing agent,complexing agent in the electroless plating process,the best electroless copper plating processwas concludedfinally.Process as follows:the copper salt was 8g/L copper sulfate,the reducing agent was 20ml/L formaldehyde,the complexing agent was 40g/L potassium sodium tartrate,the sodium hydroxide solution?20%?as the solution pH regulator to adjusted the pH value of 12¹3,the temperature of thermostat water bath was 35?and electroless plating 20min.The copper coating quality of SiC was good with this process.SiC content and sintering temperature have a great influence on themicroscopic structure of the aluminum sintered oil-impregnated bearing samples,then the crushing strength and oil content of the samplewere affected.When the sintering temperature was constant,with the increase of theSiC content,the crushing strength of samples was improvedbecause of the strengthening phase of SiC acted as a main bearing phase.But the content was more than5wt%,the strengthening phase of SiChas split the matrixand formed a bigger fragmentation effect,then result in reduced the crushing strength.The interfacial bonding was poor between SiC and Al matrix because of the wetting angle was bigger,so the hole was existed in the interface.Therefore,the increase of content has led to the quantity of the hole increased,then increased the oil content.When a certain SiCcontent added,with the increase of the sintering temperature,more and more liquid phase wasproduced,the destroyed extent of Al₂O₃ film was rose,then facilitated the formation and densification of sintering neck in the Al matrix,the crushing strength of sample increased,but radial shrinkage rate increased and oil content decreased.When the SiC content and the sintering temperature were 5wt%and 640?,the oil content and crushing strength of sample were 22.47%and 172.78MPa.Compared with the pure Al sintered billet sample,the crushing strength increased by 35.7%,the bearing sample has a good comprehensive performance relatively.When the SiC?Cu?was used as reinforced phase to enhancethe aluminum sintered oil-impregnated bearing,with the increased of theSiC?Cu?content,the crushing strength of samples was improved,oil content decreased and radial shrinkage rate increased,because of the strengthening phase of SiC acted as a main bearing phase and beared larger load.Not only wasthe metallurgical binding between the copper and Al matrix improved the interfacial bonding condition between SiCand Al matrix,and the sample densification degree increased,but also transfered the load effectively and increased the resistance when the particle slip.Meanwhile,the pinning effect produced because of copper dissolve into Al matrix,pinned the dislocation when theyslip.Therefore,the crushing strength of sintered billet sample was greatly enhanced,but oil content decreased andradial shrinkage rate increased.But too much SiC has led to the fragmentation effect increased,then the crushing strength of sample was reducedsharply.Along with the increase of the sintering temperature when the content was fixed,more and more liquid phase was produced,which made thebearing sample densification degree increased,the crushing strength of sample increased,butoil contentand radial shrinkage rate decreased.Sintered samplespreparedby10wt%¹5wt%SiC?Cu?were sintered at 610?⁶40?have reached the requirements of use.When the SiC?Cu?contentthe and the sintering temperature were 14wt%and630?,oil content and crushing strength of sintered billet were 15.20%and 242.41MPa.Compared withSiC reinforced Al matrix oil-impregnated bearing samples,the crushing strength of the bearing sample raised 40.3%.In this paper,the optimized preparation process parameters of aluminum sintered oil-impregnated bearing:addition amount ofSiC?Cu?was 14wt%,the rotational speed of ball mill was 114r/min,the ratio of ball to material is 5:1,the process control agent of anhydrous ethanol was 5wt%,the milling time was 10h,formed with 300MPa press power,the sintering temperature was 630?,thecrushing strength and oil content of bearing samples were242.41MPa and 15.20%,the sintered samples have reached the requirement of low load applications filed of oil-impregnated bearing,and can partly replacedthe iron and copper base sintered oil-impregnated bearing...