Influence of Pt on the metal-oxide interface during high temperature oxidation of NiAl bulk materials

The purpose of the investigation was to study the mechanisms improving oxide scale adherence in Pt-free and Pt-rich β-NiAl materials during high temperature oxidation. Theoretical density-functional theory (DFT) calculations were used to calculate the work of separation of the β-NiAl(1 1 1)/α-Al₂O₃(0001) metal-oxide interfaces, in pure NiAl and Pt-rich NiAl materials. The experimental work was focused on the studies of the metal-oxide interface, its development and morphology. Based on the theoretical and experimental results a complementary picture is presented for a better understanding of the Pt effect on the oxidation and oxide adhesion. It is shown that the interfacial bonding is decreased with addition of Pt to β-NiAl. The beneficial effect of Pt on the adhesion energy is attributed to the enhancement of contact areas between the oxide and the metal. The influence of Pt on the diffusion of Al and the formation of interfacial voids is also discussed.