High vacuum arc ion plating NiCrAlY coatings: Microstructure and oxidation behavior

• High vacuum AIP was developed for depositing NiCrAlY coatings at 10−3–10−4 Pa.
• Blistering occurred in low vacuum NiCrAlY coatings during oxidation at 1000 °C.
• The high vacuum NiCrAlY coatings formed purer alumina scales.
• The high vacuum NiCrAlY coatings showed dramatically better oxidation resistance.

High vacuum (HV) arc ion plating (AIP) was developed for depositing NiCrAlY coatings at vacuum levels of 10−3–10−4 Pa, which are 2–3 orders in magnitude better than that of conventional low vacuum (LV) AIP. Microstructure and oxidation behavior of the NiCrAlY coatings prepared by HV- and LV-AIP were comparatively investigated. As compared with the LV coatings, the HV coatings showed dramatically lower porosity and better oxidation resistance by forming purer alumina scales during oxidation. The significant improvements are considered to be attributed to that HV facilitated forming denser NiCrAlY coatings and eliminating gas inclusions in the coating.