Evolution behavior of carbides in 2.25Cr-lMo-0.25V steel

Abstract

The investigation was carried out on the evolution behavior of carbides precipitated in 2.25Cr-1Mo-0.25V steel during heat treatment. Four types of carbides M3C, M23Q, M7C3 and MC were identified. The mass fraction of each type of carbide was calculated and the dissolution of MC particles was found to occur during tempering. This could be caused by the annihilation of dislocations and the MC carbides precipitated on dislocations became energetically unstable and dissolved into the matrix. In addition, a two-step transformation mechanism was proposed for Cr-Fe-rich carbide. The changes in metallic composition and the average particle size of carbides were also characterized and analysed. © 2009 The Japan Institute of Metals.