Integrated Laser Additive Manufacturing of α-Al₂O₃ Nanoparticle-Seeded β/γ' Ni-Al Intermetallic Alloy with Enhanced...

The oxidation of β-NiAl at high temperatures leads to the preferential formation of metastable alumina, such as θ-Al₂O₃, which exhibits a significantly faster growth rate compared to stable α-Al₂O₃. However, our recent research has shown that through the use of the surface-dispersing nanoparticles (NPs) of metal oxides with a hexagonal closed pack (hcp), such as α-Al₂O₃, the thermal growth of α-Al₂O₃ can be facilitated. The present study employed laser additive manufacturing (LAM) to develop an integrated α-Al₂O₃ NPs surface-seeded two-phase intermetallic alloy comprising brittle β-NiAl and tougher γ'-Ni₃Al, which demonstrated better comprehensive mechanical properties. It was found that seeding the α-Al₂O₃ NPs promoted the early stage growth of α-Al₂O₃ on both β and γ' phases during oxidation in air at 1000 °C. This led to a decrease in the oxidation rate but an enhancement in adhesion of the formed alumina scale in comparison to the naked β/γ' two-phase alloy. The reasons for this result were interpreted.