An Assessment of TiN Formation on NiTi Alloy and the Corrosion Resistance of TiN/NiTi Alloy Using First-Principles Calculation

In this paper, the interfacial bonding properties between (110)_NiTi and (200)_TiN interfaces, as well as the adsorption capacity of Cl⁻ on the surfaces of (110)_NiTi and (200)_TiN, were investigated using the first-principles computational method based on density functional theory (DFT). Four types of interfacial models between (110)_NiTi and (200)_TiN were developed. It was found that the interfacial bonding energies of the four interface models are greater than zero, indicating stable interface bonding between (110)_NiTi and (200)_TiN. For comparison, model III (N of (200)_TiN is located at the bridge size between Ti and Ni in (110)_NiTi) has the largest Wad value of 9.773 J/m², which is attributed to stronger N-Ti bonding at the interface. Based on interface model III, an interfacial model of Cl⁻ at three different adsorption locations (top, bridge, and hole) on the (110)_NiTi and (200)_TiN surfaces, respectively, was constructed. The results reveal that the adsorption energies of Cl⁻ on the surface of (110)_NiTi are significantly less than those of the Cl⁻ on the surface of (200)_TiN. This suggests that (110)_NiTi is more likely to react with Cl⁻. Hence, the introduction of a TiN layer on the surface of NiTi alloy can effectively improve its corrosion resistance.