Microstructure and Property of the New Type White Cast Iron

The influences of the different Si (0.723%~4.5%) and Cr (2.0%~8.0%) contents on the microstructures and properties of Cr-Si-Mn white cast iron were investigated. It is shown that with increasing of amounts of Si and Cr elements, carbide undergoes an evident change in the morphology from the continuous net to isolated stripe and becomes clearly finer, even forms chrysanthemum-like microstructure which is usually found in high Cr white cast iron. Additionally, the amounts of the carbides increase too. The XRD analysis shows that the carbides are a mixture of Fe3C and Fe7C3 phases. Furthermore, the hardness of carbide and matrix is also found to progressively increase with increasing of amounts of Si and Cr elements. The hardness of the matrix in as-cast white cast iron is over HV400, suggesting that the matrix consists of martensite and bainite phases. The impact toughness of the samples declines evidently when Si content excesses 3.0wt%. It is also revealed that the bainite matrix in the Si-Cr white cast iron has a higher impact abrasive wear resistance than others, which is almost not dependent upon heating temperature and cooling rate. When Cr content approaches 5wt%, the impact wear resistance of the new cast iron is comparable to that of the traditional high Cr cast iron.