Effect of austenitizing temperature and cooling rate on Ms temperature of Fe–Ni–Cr cast iron

Abstract

The effect of Ms temperature variation in Fe–Ni–Cr cast iron has been investigated in this paper. The heating and cooling processes were carefully compared and analysed through in-situ observation. The results showed that the size of austenite grains remained relatively constant throughout the austenitizing process. Moreover, higher austenitizing temperatures were found to facilitate the transfer of carbon from graphite to austenite, which hindered the martensite transformation. The M3C and M23C6 carbide generated during heating and cooling diminished the concentration of carbon and alloying elements in the austenite and enhanced the Ms temperature. The acceleration of cooling rate could impede the precipitation of carbide and result in more significant lattice distortion of austenite, leading to a notable reduction in Ms temperature and an increment in residual austenite content. The augmentation in austenitizing temperature and cooling rate amplified the non-chemical driving force, culminating in a more arduous martensitic transformation.

Keywords

• Ms temperature
• In-situ observation
• Austenitizing temperature
• Thermal dilatation