Effect of Dy on oxide scale adhesion of NiAl coatings at 1200 °C

The cyclic oxidation behaviour of β-NiAlDy coatings produced by electron beam physical vapour deposition (EB-PVD) was investigated. For the Dy-free NiAl coating, numerous voids developed at the Al2O3 scale/NiAl interface and sulfur was found to segregate at the void surfaces, leading to early spallation of the scale. The addition of Dy prevented sulfur segregation and void formation at the scale/NiAl interface. As a result, the scale grown on the NiAlDy coating remained adherent and no spallation occurred even after 400 h cyclic oxidation. The 0.05 at.% Dy doped coating revealed lower oxidation rate than the more Dy doped coatings.

► β-NiAlDy coatings were produced by electron beam physical vapor deposition. ► The cyclic oxidation behaviour of the β-NiAl coatings were evaluated at 1200 °C. ► The microstructure of scale and chemistry of oxide/NiAl interface were studied.