Microstructure and carbides of as-cast high carbon martensitic stainless steel 8Cr13MoV

The solidification process of 8Cr13MoV martensitic stainless steel was calculated by using Thermo-Calc software. The solidification microstructure, morphology and type of carbides were analyzed by optical microscopy, scanning electron microscopy and X-ray diffraction. The static continuous cooling transformation curve was measured by Gleeble thermal simulator. The results indicate that the microstructure of 8Cr13MoV includes ferrite and M₂₃C₆ under the equalized solidification condition, while ferrite, martensite, retained austenite, M₇C₃ and M₂₃C₆ in the practical solidification condition. The main carbides are M₇C₃, and a small number of M₂₃C₆ with lamellar or dendritic morphology distribute on the grain boundaries, which can be attributed to element segregation. Because of high C and Cr contents, austenite can transform to martensite at a cooling rate of 0.1℃·s^-1.