High-throughput preparation and quick characterization of oxidation behaviors of complex Al–Cr compositional gradient coatings on a novel Co–Al–W–based superalloy prepared using multi-arc ion plating technology

Abstract

The early oxidation behaviors of complex Al–Cr compositional gradient coatings on a novel Co–Al–W substrate prepared by multi-arc ion plating technology (MIPT) at 1000 °C for 20–60 min were rapidly characterized. The as-deposited coatings with compositions ranging from (55%–90%Al, 45%–10%Cr) exhibited the laminated structure α-Al + Al₈₀Cr₂₀+Al₈Cr₅+α-Cr. After annealing at 640 °C for 40 h, a two-layered coating composed of (Co(Al, Cr) + Al₈Co₁₈Cr₄) and IRL formed, and the thickness of the coating increased from the 14–18 μm of the as-deposited state to 25–35 μm. During oxidation at 1000 °C for 20–60 min, a three-layer structure consisting of an outer α-Al₂O₃+α-Cr₂O₃+CoCr₂O₄ layer, a central unoxidized Al–Cr layer, and an inner μ-Co₇(W_0.55Cr_0.45) ₆+B₂–CoAl layer formed on the substrate. The Al–Cr coatings with higher Cr content had a looser oxide layer due to the CoCr₂O₄ phase, which might degrade the intended protective effect of the Al–Cr coatings. Thus, the Al–Cr coatings with higher Al content were suitable for preventing oxidation behavior. This work proposes a high-throughput screening method for rapid characterization of the early oxidation mechanism of the complex Al–Cr compositional gradient coatings.