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(W0.55Cr0.45) 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.