Effect Of Sintering Process And Alloy Element On Microstructure And Mechanical Properties Of Cu-Based Oil-impregnated Bearing

Powder metallurgy Cu-based oil-impregnated bearing has wide applications in mechanical manufacturing industry. However, the shortcoming of Cu-based oil-impregnated bearing is weak bearing capacity and poor wear resistance. In the present work, the affection of the sintering process on microstructure and properties of CuSn10 oil-impregnated bearing materials had been investigated. In order to reduce the cost of conventional CuSn10 porous bearing, Mg was added to replace partial Sn. The affection of the content of Mg on the properties of Cu-Sn-Mg oil-impregnated bearing materials had been investigated. CuSn10 pre-alloyed powders were used to prepare the Cu-based oil-impregnated bearings, and technology of the bearings for high performance starter are developed.The results indicated that powder particle surface is oxidized seriously when the samples were sintering at 720? for 90 min under argon atmosphere, and there are a great number of large and irregular pores. With the increasing of the content of H2 in the sintering atmosphere, the pore amount and size decrease with the pore shape closing to spherical. The oil content of the sample is decreased, and the oil-bearing density, radial crushing strength and hardness of the sample are increased, the wear rate is reduced firstly and then increased. The samples were sintered under 50%H2+50%Ar atmosphere(volume percent). When the sintering time was increased from 30 min to 120 min at 720?, the pore size and amount is reduced. The oil-bearing density, mechanical properties and wear rate of samples are increased. When the sintering temperature was increased from 680? to 720?, the pore size and amount is reduced. The density and mechanical properties of oil-bearings are increased; the wear rate is reduced.The samples were sintered at 800? for 30 min under 50%H2+50% Ar atmosphere. In Cu-6wt%Sn sample, there are a great number of small pores and a little large pores. In Cu-6wt%Sn-1wt%Mg sample, the small pore amount is reduced and the large pore amount is increased. The oil content, radial crushing strength, hardness of the sample are increased to 23.8%, 142 MPa and 35.2HB. With the increasing of the content of Mg in the sample, the small pore amount is reduced and the large pore amount is increased continuously. There are a lot of MgO in the hole of material. The samples are swelling and the expansion ratio is increased. The oil content of the samples is decreased, the radial crushing strength and hardness of the sample are increased. With the increasing of the content of Mg in the sample, the wear rate and the coefficient of friction are reduced firstly and then increased. There are a little of MgO in Cu-6wt%Sn-1wt%Mg sample. It?s friction surface has formed protective oxidation. At the same time, the sample with homogeneous pore distribution and high oil content and high porosity is available under sintering. So the the wear rate and the coefficient of friction of the sample is lowest.The preparation process for high properties PM bearing for automobile starter were developed with CuSn10 pre-alloyed powder. Properties test and load-and-test results show that the PM bearing reaches the design requirements.