Effect of dysprosium addition on the cyclic oxidation behaviour of CoNiCrAlY alloy

Abstract The cyclic oxidation behaviour of a Co32Ni21Cr8Al0.6Y (wt.%) alloy with and without the addition of 0.2 wt.% dysprosium was investigated at 800 and 1100 °C in static laboratory air. The Dy-containing alloy showed a faster θ - to α -alumina transformation and significantly less weight gain than Dy-free alloy. Under cyclic oxidation at 1100 °C, Dy addition produced a continuous and protective Al 2 O 3 scale. The Dy-free alloy exhibited poor oxidation resistance. Scale spallation led to the development of a complex oxide scale and internal precipitation: (Al,Cr) 2 O 3 on the surface, followed by a Al 2 O 3 layer, then (Al,N) precipitates alone beneath the external scale.