Martensite transformation kinetics in 9Cr-1.7W-0.4Mo-Co ferritic steel

Martensite transformation features in the 9Cr-1.7W-0.4Mo-Co ferritic steel, was conducted on a Netzsch Differential Thermal Analysis (DTA), after austenitized at 900 °C and 1150 °C followed by cooling at various rates to room temperature were studied. A martensite transformation kinetics model based on assumption of continuous nucleation and consideration of impingement was introduced to investigate the influence of austenitizing temperature and cooling rate on the martensite transformation behaviors. The obtained interface velocity and the activation energy for interface-controlling growth are lower than 10−5 m/s and 40 kJ/mol, respectively, according to the fitted data. Both indicated that martensite transformation in the 9Cr-1.7W-0.4Mo-Co ferritic steel was controlled by nucleation rate, and that growth of plates was controlled by thermal activation of atoms.