Study on In Situ Formation of Intermetallic Compounds and Oxygen Adsorption of Ni/Al Coating

In order to predict the formation order of nickel-aluminum compounds. The first-principles calculation method is used to calculate the intermetallic compound formation mode of Ni/Al coating using the thermodynamic properties obtained by the phonon spectrum, and an effective formation-free energy model is presented. The calculated results were verified with experiments. Ni coating was deposited on the pure titanium surface by plasma spraying, and Al coating was prepared on the Ni layer by arc spraying. Finally, the in situ reaction products between Ni/Al layers were studied by vacuum heat treatment. The results show that the calculated formation order of Ni-Al compounds is NiAl 3 → Ni 2 Al 3 → NiAl → Ni 3 Al which is consistent with the results obtained experimentally. In order to further study the oxidation resistance of the NiAl phase, the adsorption of O atoms at different positions on the NiAl (110) surface was calculated, moreover verified by a high-temperature oxidation test. The results show that O atoms are preferential sorptioned at the Al–Al bridge site on the NiAl (110) crystal plane, and the adsorption energy is − 10.51 eV. O atoms are more priority bonded to Al atoms to form Al 2 O 3 with oxidation resistance. After heating at 800 °C for 100 h, the coating surface is mainly Al 2 O 3 formed by the reaction of Al atoms in the NiAl phase and oxygen, and the coating has good high-temperature oxidation resistance.