2005 Volume 77 Issue 5 Pages 293-300
Effect of chemical composition on the microstructure and characteristics of Ni-hard cast iron has been investigated in order to improve the wear resistance and other material properties by precipitation of hard M7C3 carbide and graphite.
A small amount of graphite and M7C3 type carbide crystallize together in the cast iron of the composition of 2.6mass%C-7.0mass%Cr. The volume fraction of graphite increases with an increase in carbon content. Nickel has a strong effect on the transformation of matrix and the highest hardness is obtained in the cast iron containing 5.0mass%Ni in as-cast state, because of the transformation of austenite to martensite. Tensile strength decreases as carbon content gets over 2.6mass%. Heat crack length is the shortest in the cast iron of 2.6mass%C, and wear loss and amount of sticking decrease with increasing chromium and molybdenum contents. It was found that the optimum chemical composition of high chromium Ni-hard cast iron containing M7C3 type carbide and a small volume fractionofgraphiteis 2.6mass%C-2.5mass%Si-5.0mass%Ni-7.0mass%Cr-2.4mass%Mo, to improve the wear resistance remaining good mechanical properties of conventional Ni-hard cast iron.
