Simulation and verification of core–shell MC carbide design in Fe–C–Ni–V–Ti steel

Thermodynamic theory was used to calculate the formation temperature and site fraction of MC carbides in Fe–C–Ni–V–Ti system. The calculation results showed the theoretical formation conditions of core–shell MC carbides. One-step and two-step heat treatment processes were used in Fe–C–Ni–V–Ti alloy to, respectively, obtain homogeneous and core–shell MC carbides, which was consistent with the thermodynamic calculation results. The transmission electron microscopy observations showed that the core–shell MC carbide obtained by the two-step heat treatment process contained homogeneous (Ti, V)C as the core and basically VC as the shell. The mechanical test results proved that compared with homogeneous MC carbides, core–shell MC carbides could improve the basic mechanical properties of the alloy because VC shell greatly increased the bonding strength and separation work of Fe/MC interface. Thus, the core–shell MC carbide with a VC shell structure can be a better grain refiner and can be used in steels with a high standard of fracture toughness.