Non-equilibrium precipitation behavior of TiC during rapid solidification of TiC-reinforced wear-resistant steel

Precipitation behavior of TiC in TiC-reinforced wear-resistant steel was investigated using both thermodynamics and experiments. The carbide in TiC-reinforced wear-resistant steel is principally Ti-rich MC-type, which starts to precipitate at 1 460°C in the solid–liquid zone. As the temperature decreased, there is no major change in the concentration of Ti and C in TiC. The results calculated by using equilibrium assumptions show that TiC can form when the solid fraction exceeds 0.24. However, the isolated primary TiC was observed in the sample cooled at rate of 162 K/s and 267 K/s, indicating that TiC can precipitate from the melts at the initial stage of solidification process. As an extension of Brody and Fleming’s model, the interface response functions relating the cooling rate with the interface composition and interface temperature, which consider interface non-equilibrium effect on the basis of incomplete mixing of solute in the liquid during solidification, were used to evaluate TiC precipitation behavior during rapid solidification for different cooling rates. In comparison with lower cooling rate, the effect of non-equilibrium behavior is strengthened under the condition of higher cooling rate, so that primary TiC can precipitate from the melts at the initial stage of solidification when a high cooling rate is imposed.