Refining carbide dimensions in AISI M2 high speed steel by increasing solidification rates and spheroidising heat treatment

Abstract

Obtaining small and spherical carbides is crucial but difficult for high speed steels. The present work attempts to refine the carbide dimensions in M2 steel by the combination of changing eutectic carbide morphologies and spheroidising heat treatment. With increasing solidification rates, M₂C eutectic carbides evolve from the plate-like shape into the fibrous one. The morphology of M₂C changes remarkably during heating, the process of which includes carbide decomposition, dissolution, spheroidisation and coarsening. Compared with plate-like carbides, the fibrous carbides are much easier to decompose and spheroidise, obtaining small and spherical carbides. Thermodynamic and kinetic studies of the heating process were conducted to clarify the mechanisms of carbide refinement.

Keywords:

• High speed steel
• Eutectic carbide
• Dimension
• Spheroidisation

The present research was financially supported by the Fund of Transformation of Scientific and Technological Achievements from Jiangsu Province (grant no. BA2010139) and the opening project of Jiangsu Key Laboratory of Advanced Metallic Materials (grant no. AMM201203).