Study on decomposition behaviour of M 2 C 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.