| The Waste of materials and energy sources has become a serious obstacle in modern industry and agriculture development. In all kinds of wear styles, the abrasive wear nearly occupies 50% of wear total quantity. At present the preparation of wear-resistant composite layer on components has become an important measure to improve wear-resistant of machinery parts.At present, the measures preparing wear-resistant composite coating with a certain engineering thickness include overlaying,brazing,laser cladding,cast-in-place surface alloying and powder metallurgy,etc. By using these coating techniques, it is impossible to prepare composites coatings with high wear resistance on components. The coatings improve the wear-resistant of components surface and make components have longer service life.The unsmoothed characteristics of some living beings in soil have wear reduction and wear resistance function . The research benefits the revelation that a tungsten carbide(WC) reinforced Cu-base alloy wear-resistant composite coating was produced on mild steel by spark plasma sintering (SPS).Under the condition of two bodies abrasive wear ,the coating with the structure that hight hardness and good wear resistance WC particles embedding in tough fine Cu-base alloy matrix resist the abrasion wear and manifest the good wear reduction and wear resistance properties that the unsmoothed bodysurface of some living beings in soil have.SPS is a new process of rapid sintering technics. The instantaneous, intermittent and high-powered electric pulse is applied in die where the powders are put in. The high-powered electric pulse can generate plasma among powder particles,resulting in cleaning effect,activation effect and uniformization effect ,etc. It's properties include uniform heat up, low sintering temperature and short sintering time . It can produce high compact materials with fine and uniform structure. By using this technique, it is impossible to prepare composite coating with the adjusted arbitrarily thickness. At present ,there were many studies on the wear-resistant composite coatings,but no research groups besides the author's research group concerned about the WC/Cu–base alloy wear-resistant composite produced by using SPS. The following research works have been conducted in this paper. Firstly, the normal test was utilized for optimization of technique parameters of SPS , the weight fraction and dimension of reinforcing particles in order to obtain better wear resistance. The optimal results of reinforcing particles weight fraction and dimension and technique parameters have been obtained as following: WC particles weight fraction of 50%, WC particle dimension of 45-55 mesh, sintering pressure of 30Mpa, perform preheated temperature of 700℃,heat up speed of 150℃ per minitue, heat preservation for 5 minitues.Secondly, the structure of the coating was investigated . The research results have been obtained as following.(1) In the specimen that WC/Cu-base alloy composite coating reinforcing mild steel , The optial micrstructure of the composite coating indicated that WC particles are distributed homogeneously in the Cu-base alloy matrix and the crystal grains of the Cu-base alloy are fine and uniform . WC particles combine strongly with the alloy matrix. There no obvious pore in the coating.(2) There exists two interfaces in the coating-substrate system. One is the inner interface between WC and Cu-base alloy in the coating,the other is the coating/substrate(mild steel) interface.With EDS(SEM) analyses, the elemental distributions across the interfaces were investigated. The research results show that elemental diffusion and light metallurgy action was occurred in the interfaces.(3)The results of XRD examinations manifest that the phases of the coating consist of WC ,WC2 , αphases-the solution that Zn dissolve in Cu andβphases-CuZn compound .Lastly, the abrasive wear properties of the composite coating and the wear-resistant mechanism were investigated .The research results have been obtain as...
|
PDF Full Text Request