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.