Cr microalloying enables high thermal stability of interphase-precipitated alloy carbides in low carbon ferritic steels

The coarsening of interphase-precipitated carbides in hot-rolled ferritic steel products during coiling is an intractable issue as it will significantly deteriorate the mechanical performance due to the weakened precipitation hardening effect. In this contribution, we propose a useful but cost-effective approach to tune the thermal stability of interphase-precipitated carbide. By adding a small amount of Cr, we achieve an enhancement of coarsening resistance for both TiC and (Ti, Mo)C, with a more pronounced effect on the latter. Meanwhile, when the Cr addition is combined with Mo, it enables superior mechanical performance of the Ti-microalloyed steels through carbide refinement and pearlite inhibition. The underlying origins are addressed in terms of the Cr role in the interfacial energy of the carbide/matrix interface by first-principles calculations. These findings provide a new insight into optimization of thermal stability of multiple alloyed carbides.