Selection of Eutectic Carbides in Multi-Component High Speed Steel Type Cast Irons

摘要

High speed steel type cast iron to maintain high wear resistance and fracture toughness is neces-sary to control eutectic carbides, MC, M_2C, M_7C_3, M_6C and M_3C. To predict carbide formation under certain solidification conditions of multicomponent cast iron, quantitative eutectic selection criterion is needed. Interface undercooling, Ar, for eutectic growth was given as a function of growth rate, V; DELTA T = kV~(1/2). Interface temperature of each eutectic carbide formed in Fe-M-C (M; Cr, V, Mo) Systems; gamma+M_3C and y +M_7C_3 eutectics in the Fe-C-C System, gamma +VC eutectics in Fe-V-C System and gamma +M_6C and gamma +M_2C eutectics in Fe-Mo-C System, was measured during unidirectional solidification. The k values of eutectic carbides were then estimated. Relationship between k, carbide spacing and growth rate was discussed. Application of k values obtained in ternary Systems to the eutectic selection map and also to more multicomponent Systems was discussed.