Effect of Nitrogen‐Substituted Carbon on Thermal Stability of Cr‐Mo‐V Hot‐Working Die Steel
Lihao Li, Wei Zhang, Jinbo Gu, Wang Li, Fanghong Xu, Jingyuan Li
Abstract
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.