Effect of Nitrogen-Substituted Carbon on Thermal Stability of Cr-Mo-V Hot-Working Die Steel

To extend service life of Cr-Mo-V hot-working die steel, a method of alloying with nitrogen-substituted carbon is proposed. The mechanical properties of the test steels in the long-time heating and holding process are measured. The effect of nitrogen-substituted carbon on thermal stability is characterized and analyzed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Thermo-Calc. The results show that the ratio of N in V(C,N) can be increased by nitrogen-substituted carbon at high temperature, which significantly improves its stability. As a result, it can not only refine the grain but also broaden the austenitizing temperature range and promote the complete solution of alloy elements such as Cr, Mo. In the process of long-term heating and insulation, nitrogen-substituted carbon can effectively reduce the precipitation of harmful carbides and the coarsening rate by raising the activation energy of tempering transformation with 20.0 kJ mol(-1), and increase the precipitation of the main strengthening phase V(C,N). Nitrogen-substituted carbon, as an effective alloying method, innovatively improves thermal stability and service life of Cr-Mo-V hot-working die steel.