Study On Fabrication And Performance Of A Vanadium Reinforced Gradient Wear-resistant Materials

The wear resistance of metal materials has received great concerns in the fields of machinery and materials. The metals with single performance could not fit the requirements in practical applications that need parts both with good hardness external and high strength internal. The concept of Functionally Gradient Materials (FGM) provides a new solution for wear resistant material, so that people try to improve part lifetime by using the gradient composites, which are prepared by changing microstructure of the material through the methods of powder metallurgy, semi-continuous casting, casting infiltration, etc. However, these preparations of FGM are complicated for the controls of parameters that are not suitable to manufacture in large quantities of wear-resistant parts. In order to provide an experimental basis for mass production of wear resistant material, the research studied on the in-mold melting process by bimetallic composite casting process to prepare a wear resistant material.In the in-mold melting process, the pre-placed high-vanadium alloy-rods were melted by high temperature liquid steel and the atoms of alloy elements moved to the matrix. After solidification, the elements and carbide were gradient distribution in the material, which create the gradient changes of mechanic properties.According to the theory of in-mold melting and diffusion, we analyzed the melting process of alloy-rods in liquid metal. And based on the Fick's second law, the concentration equation was deduced and its fundamental solution was obtained by using the integral transformation method. Moreover, the diffusion process of vanadium in liquid metal was simulated by considering the experimental factors of mold size, alloy-rod size and diffusion coefficient and etc.Microstructure of the diffusion component was examined by OM, SEM and XRD, and alloy elements in the diffusion layer were studied by EDS, and the hardness of the material was tested by HRS. The results showed that the material had gradually changed hardness, which is due to the uniformly existents of carbide particles on martensite matrix and the gradient distribution of vanadium and carbide.The design of the gradient wear resistant material preparation, the analysis of the melting and diffusion process theory, the simulation of the elements diffusion process and the investigation of the microstructure and properties, we solve the problem about properties gradient changed in materials, which provides a new method for the manufacture and process improvement of wear resistant parts.