Surface hardening of ductile cast iron using stainless steel

A surface hardening technique for improving the wear resistance of ductile cast iron (DI) is proposed by fabricating molten DI with stainless steel. The essential idea is concerned with using the chromium source in stainless steel and the carbon source in DI to form chromium carbides. It was demonstrated that the surface of the fabricated DI consisted of firstly a layer of high chromium white cast iron ((Cr,Fe)7C3 eutectic carbides), which was originally stainless steel, and then a layer of medium low-chromium white cast iron ((Fe,Cr)3C eutectic carbides), which was originally DI. Thus the hardness of the surface layer became 2–3 times that of the baseline ductile cast iron. Applying austenitic stainless steel produces a much better hardening effect than applying ferritic stainless steel. The depth of the hardened surface layer depends on the pouring temperature of the iron melt, the wall thickness of the iron casting and the cooling rate of the casting mold. The present strategy is, in principle, possibly applied to complete as well as local surface hardening of various kinds of ductile iron castings.