Oxidation resistance and thermal insulation performance of Al–Cr–O/Zr–O + NiCoCrAlSiY and Al–Cr–O + NiCoCrAlSiY coatings prepared by arc ion plating

Al–Cr–O/Zr–O multilayer coating + NiCoCrAlSiY bond layer and Al–Cr–O single-layer coating + NiCoCrAlSiY bond layer were deposited on superalloy by arc ion plating, and subsequently they were heat treated at 1000–1200 °C. Scanning electron microscope and X-ray diffractometer were used to analyze the microstructure and phase of the coatings. The results showed that both the Al–Cr–O/Zr–O multilayer coating and Al–Cr–O single-layer coating exhibited a compact spherical structure. After heat treatment, cracks occurred on the surface of Al–Cr–O/Zr–O coating. Cracks increased and widened with rising the temperature. However, the surface cell clusters of Al–Cr–O coating after heat treatment were changed to tightly connected granular structures, and the granular structures grew up significantly with the increase of annealing temperature. Owing to the oxygen ion conductor and lower densification of t-ZrO₂ than α-Al₂O₃, t-ZrO₂ in the Al–Cr–O/Zr–O coating provided an access for the inward diffusion of oxygen. Therefore, the high temperature oxidation resistance of the Al–Cr–O coating + NiCoCrAlSiY layer was superior to that of the Al–Cr–O/Zr–O multilayer coating + NiCoCrAlSiY layer. The thermal insulation performance of Al–Cr–O/Zr–O multilayer coating + NiCoCrAlSiY layer was better than that of Al–Cr–O coating + NiCoCrAlSiY layer due to the large thickness and low thermal conductivity of t-ZrO₂ phase and the heat reflection of interlayer interface.