COARSENING RESISTANCE OF M2C CARBIDES IN SECONDARY HARDENING STEELS .2. ALLOY DESIGN AIDED BY A THERMOCHEMICAL DATABASE

Abstract

In high Co-Ni steels containing the strong carbide-forming elements Mo, Cr, and W, secondary hardening is accomplished by the precipitation of fine-scale M2C alloy carbides. Thermodynamic stability and coarsening resistance of these carbides depend on the alloy content of these elements. A model for the M2C coarsening kinetics in multicomponent alloys has been used to identify the optimum alloying addition for maximum coarsening resistance and as a basis for selection of four experimental alloy steels. Necessary information pertaining to the equilibrium in these steels was obtained using the Thermo-Calc software and database developed at the Royal Institute of Technology, Stockholm, Sweden.