Effect of Heating Temperature on Decomposition Transition Behavior of M2C Carbide in High-vanadium High-speed Steel

Based on the need of high wear resistance， a new kind of high-vanadium high-speed steel named W3Mo4Cr5V6 was designed. The transformation behavior of metastable M2C carbides in the high temperature heating process of the steel was analyzed by means of SEM and EMPA. The results show that the cophortic M2C carbide will undergo M2C+γ-Fe→M6C+MC+M7C3 transition at high temperature heating process.A large number of W， Mo-rich M6C and a small amount of V-rich MC and Cr-rich M7C3 are formed around the Mo and W-rich M2C phase. With the increase of temperature from 950 ℃ to 1 150 ℃， the high temperature transformation of M2C carbides gradually tends to be complete and the fibrous M2C is easier to decompose and transform than lamellar M2C， and the lamellar or fibrous morphology distributed in the austenite grain boundary with discontinuous network is transformed into the granular morphology distributed at the grain boundary， which can effectively reduce the harm of network carbides to the grain boundary. The research can provide an effective reference for the composition and morphology control of carbides distributed at the grain boundaries of high-speed steel and the optimal selection of parameters such as temperature and time of hot processing and heat treatment process.