Solidification Microstructure of AISI M2 High Speed Steel Manufactured by the Horizontal Continuous Casting Process.

In the present work, AISI M2 high speed steel is produced by the horizontal continuous casting process. The difference of solidification microstructure in ingots by mould casting and continuous casting has been examined by means of scanning electron microscope (SEM), electron back-scatter diffraction (EBSD), transmission electron microscope (TEM) and high resolution electron microscope (HREM). The results show that the as-cast structure consists of iron matrix and networks of M₂C eutectic carbides, which are greatly refined in the continuous casting ingot compared to the case of ingot by mould casting. Meanwhile, the morphology of M₂C eutectic carbides changes from the plate-like shape into the fibrous one. Micro-twining and stacking faults are observed in the plate-like M₂C, whereas they are rarely identified in the fibrous M₂C. Based on the characteristic of morphology and microstructure, it is expected that the plate-like M₂C is a faceted phase while the fibrous M₂C is a non-faceted phase. [ABSTRACT FROM AUTHOR]