LAUSR

The precipitation kinetics of TiC and VC during high-temperature tempering of low-carbon martensitic steels was studied by means of hardness measurement and theoretical analysis. The precipitation–temperature–time diagram, which was determined through the hardness versus tempering time curves, shows that the precipitation rate of TiC is more rapid than that of VC at 600 °C or above, while they are almost the same at 550 °C. The number density of TiC precipitates is larger than that of VC precipitates, thus leading to a larger secondary hardening effect. An analytical model to describe the precipitation kinetics of microalloying carbides during tempering of martensitic steel was presented. Using this model, the difference of precipitation kinetics between TiC and VC can be well explained, in terms of the shape and relative position of kinetics curves and the nose temperature.