Study on decomposition behaviour of M2C eutectic carbide in high speed steel

The present work has investigated the decomposition behaviour of M2C eutectic carbides with different morphologies in high speed steels. Both plate-like and fibrous M2C carbides decompose into M6C and MC at high temperatures, the decomposition of which is controlled by the diffusion of alloying elements in carbides. However, they are different in the decomposition process and thermal stability. Compared with plate-like M2C, fibrous M2C carbides are less stable, depending on the decomposition process. MC carbides are nucleated at the interface of fibrous M2C/matrix, whereas they are nucleated inside plate-like M2C carbides. The matrix plays different roles in the decomposition. It provides W, Mo and V for the decomposition of fibrous M2C and Fe for the plate-like M2C.