Investigation and modification of carbide sub-systems in the multicomponent Fe-C-Co-Cr-Mo-Si-V-W system

New experimental phase equilibria information a out the Fe-C-Co-Cr-Mo-Si-V-W system and sub-systems are presented and used to modify the thermodynamic description of the system. The main interest was focused on the composition of the MC, M7C3 and M6C carbides and the necessary adjustment between the carbide-forming elements. A new set of thermodynamic parameter values describing the Gibbs energy of different phases was obtained utilizing phase equilibria data from model alloys. A number of calculated sections of binary systems and ternary carbide systems are presented and compared to both new and old experimental information. Calculations of commercial alloys to verify the improvements in multicomponent systems are also presented. The present calculation using the Thermo-Calc software shows much better agreement with the new experimental results than previous assessments.