Research On Preparation And Tribological Properties Of WS₂-Contained Copper-Steel Bimetal Lead-free Solid Self-lubricating Materials

Self-lubricating materials exhibit superior performances in many special working conditions where the traditional lubricating oil and grease can not meet the operating requirements. Currently almost all the widely used copper base solid self-lubricating composite materials contain lead. In order to meet the purposes of green environmental protection and international lead ban, it is urgent to produce lead-free copper-based solid self-lubricating materials. This paper adopted CuSn8Ni3as the substrate to prepare WS2-contained copper-steel lead-free solid self-lubricating materials by powder metallurgy of apparent sintering method. Besides, this paper systematically studied the preparation process of the materials and the sintering behaviors of WS2int he materials during sintering process, and the mechanisms of friction and wear behavior with and without oil. Moreover, the research results provide the theory basis for the realization of lead-free copper-based solid self-lubricating materials.(1) New copper base lead-free solid self-lubricating materials can be prepared through the powder metallurgy sintering process. The preparation process includes:Laying powder-Sintering-Rolling-Re-sintering (Annealing)-Finish rolling-Roll smoothing. The specific sintering processes are as follows:the first sintering. The temperatures820±10℃with holding time from25to35min and the re-sintering temperatures800±10℃with heat preservation for15to30min.(2) In the sintering process, WS2will react with the substrate in copper alloys to form new phases such as copper sulfide and W, with no loss of S. With the increase of WS2content, the initial porosity increased gradually after the first sintering, while the hardness is reduced. Rolling and re-sintering technology can increase the hardness of Materials, because the W phase produced during the high temperature sintering can pin the dislocations and reinforce particles.(3) The content of WS2has important influence on the friction and wear performances of copper-based lead-free solid self-lubricating materials. The self-lubricating mechanisms with oil or not are quite different from each other. The lubricating film formed in oil plays a main role in lubrication of materials, while influences of WS2on friction and wear properties are due to the generation of W and cu sulfides under the condition of dry friction. The results show that it is detrimental wit the content of WS2too high or too low. When the content of WSt is3%, the friction coefficient reaches the minimum value, and materials obtained the best wear properties.(4) With comparison of the material containing3%WS2by powder metallurgy and CuSn10Pb10bearing shell materials, it is found that, in the same friction and wear conditions, the new material has similar friction and wear properties to the CuSn10Pb10, and the dry friction and wear performance of the new material is better than CuSn10Pb10bearing materials.