Oxidation Behavior Across Composition Space Relevant to Co-based γ/γ′ Alloys

A multi-source ion-plasma deposition technique was used to create a series of three combinatorial libraries across the Co-Ni-Al-W-Cr-Ta composition space relevant to the formation of Co-based γ/γ′ microstructures. Alloys were isothermally oxidized for 1 hour in air at 1100 °C, and screened for Al₂O₃ scale formation using a high-throughput photo-stimulated luminescence spectroscopy technique. Select compositions were then analyzed in cross-section via EDS in the SEM and TEM. The resulting oxide microstructures are presented, and paths to explain their evolution are proposed. Compositions forming α-Al₂O₃ with thinner amounts of overlying oxides are highlighted. The thinnest scale observed was ~ 1 μm, comparable to second-generation Ni-base superalloys oxidized under the same conditions.