Effects of Dy on transient oxidation behavior of EB-PVD β-NiAl coatings at elevated temperatures

β-NiAl is a potential oxidation-resistant coating material to be operated at temperatures above 1 150 °C. In this paper, β-NiAl coatings with 0-0.5 at Dy are prepared by electron beam physical vapor deposition (EB-PVD). Transient oxidation behavior of the coatings is investigated. At 1 200 °C, only stable α-Al₂O₃ phase is observed on the 0.05 at doped coating, whereas the phase transformation from θ-Al ₂O₃ to α-Al₂O₃ occurs in the 0.5 at Dy doped coating during 1 h oxidation. At 1 100 °C, all the coatings reveal the transient transformation of θ-α in the early 15 min and the transformation for the 0.05 at Dy doped coating is completed within 45 min, much earlier than that for the 0.5 at Dy doped coating. Overdoping of Dy retards the transformation of θ-α. The undoped and overdoped coatings reveal the whisker structure of θ-Al₂O₃ even after 20 h oxidation at 1 100 °C, while the 0.05 at Dy coating reveals typical granulated structure of α-Al₂O₃.