Research On Ultra-high Hardness And Impact Toughness Of Low Alloy Wear Resistant Steel

Wear is one of the three manners (corrosion, wear, fracture) for material failure, which has caused huge material losses and waste of resources. Therefore, the research and development of wear-resistant materials with good performance have important economic significance. The effects of heat treatment, carbon, nickel and vanadium alloy elements on microstructure and mechanical properties of wear resistance steel, used in bucket tooth, were investigated in this topic using EPMA, EDS, TEM and XRD methods. And also, the laws of effect of heat treatment on microstructure and mechanical properties were preliminarily studied.(1) Definition of chemical composition of low alloy wear resistant steel. 10 ingots with various contents of elements including C, Si, Cr, Ni, Mn, V, and B were designed in this research. In the metal founding embrittlement occurred in the ingots that contains B alloy element, which made it impossible to make further research, while the rest ingots were available.(2) Effect of heat treatment on microstructure and mechanical properties of low alloy wear resistant steel. The effect of homogenization on microstructure, quenching temperature and tempering temperature on microstructure and mechanical properties were studied through the heat treatment tests on low alloy wear resistant steel with different alloy elements. It was illustrated that the homogenization could eliminate the segregation between the dendrites. A good combination of hardness and toughness can be got when was quenched at 940℃and tempered at 260℃, which were 48HRC and 24J measured at -40℃of V notch, respectively. The microstructure of the specimen was consist of lath martensite, retained austenite and diffused tiny carbides.(3) Effects of alloy elements on microstructure and mechanical properties of low alloy wear resistant steel. The effect of C, Ni and V alloy elements on microstructure and mechanical properties and hardenability were mainly researched. Specimens containing different alloy elements were prepared in the same heat treatment. Specimen containing higher carbon content showed excellent hardness value with more carbide in its microstructure. Specimen with nickel in it had a higher impact toughness value as more retained austenite and bigger martensite bundles in its microstructure, while specimen containing vanadium exhibit nice hardness value with the quantity of carbides increase. Elements solved in austenite such as Ni, Mn and C could improve the hardenability while elements forming carbides such as V decrease the hardenability.