Development of microstructure during heat treatment of high carbon Cr-Mo steel


Stainless steels containing enhanced chromium and carbon contents are particularly attractive for applications requiring improved wear and corrosion resistance. The as cast microstructure of such steels is composed mainly of ferritic matrix along with a network of interdendritic primary carbides. It has been shown that heat treatment of these steels results in microstructures that contain more than one type of carbide. A selective dissolution technique has been employed to isolate carbides from the matrix. Scanning electron microscope and X-ray diffraction studies of the as cast steels have shown that the primary carbides are essentially of M7C3 type, whereas in heat treated specimens both M7C3 (primary) and M23C6 (secondary) type carbides have been observed. The relative amounts of these carbides are found to be dependent on the heat treatment temperature. In addition, nucleation of austenite occurs above 950°C and at ∼1250°C the matrix transforms entirely to austenite, which is retained completely on quenching to room temperature. © 1999 IoM Communications Ltd.

Publication Title

Materials Science and Technology