CHEMISTRY, METALLURGY AND MECHANISM OF MICROSTRUCTURAL TRANSFORMATION IN HADFIELD STEEL, HIGH CHROMIUM CAST IRON AND AUSTEMPERED DUCTILE IRON

Three ferrous materials; Hadfield steel, high chromium white cast iron and austempered ductile iron (ADI) exhibit a similar phenomenon in which soft stabilised austenite transforms to hard martensite on the worked surface. This property is desirable in applications where toughness is required in the bulk of the component while the surface needs to be hard-wearing. Thus, the microstructure of the component may consist of metastable austenite, which is meant to change to martensite by strain-induced transformation as a result of impact or wearing loads applied to the surface. The chemistry of alloys is very different while the metallurgy and transformation mechanisms are closely similar. In this paper, the differences, similarities as well as the most appropriate applications of the materials are discussed.