First-principles study on TiC/TiN heterogeneous nucleation interface in high-titanium steel

A systematic study using the first-principles method was conducted to investigate the interface relationship between TiC and TiN in high-titanium steel, where TiC nucleates and grows with TiN as the core. The results showed that the energy of the (111) surface depends on the type of terminal atoms, with the Ti-terminated surface exhibiting lower surface energy than the C(N)-terminated surface. In contrast, the energy of (100) and (110) surfaces was independent of the terminal atom type. The order of surface energy determined to be (111)-Ti<(100)<(110)<(111)-C(N), the work function exhibits the same trend, while the stability is exactly the opposite. Among all interface structures, the interface structure with Ti-C terminal atomic combination was identified as the most stable, which can be attributed to the formation of covalent, ionic, and metallic bonds at the interface. The bonding strength primarily arises from the hybridization between Ti-d orbitals and C(N)-p orbitals. Within the (111) interface structures, metallic bonds were formed in the interface structure with the Ti-Ti terminal atomic combination, leading to the lowest interface energy and making it thermodynamically the most stable. Consequently, TiC is capable of heterogeneously nucleating on TiN, with the preferred nucleation surface of TiN following the order of (111)>(100)>(110).