Abstract
Isothermal oxidation in air was carried out on a gamma'-strengthened single crystalline Co-Al-W-B superalloy at 800, 900, and 1000 degrees C. The absence of grain boundaries leads to inferior oxidation properties at 800 and 900 degrees C, and improved properties at 1000 degrees C, compared to a polycrystalline alloy of the same composition. At lower temperatures, grain boundary diffusion is dominant and assumed to be the reason for enhanced B-accumulation in the inner oxide layer and enhanced formation of the protective inner Al2O3 layer. However, at 1000 degrees C superior oxidation resistance of the single crystalline superalloy can be observed. (C) 2013 Elsevier Ltd. All rights reserved.