Effect of yttrium on high temperature oxidation behavior of Ni-Al-Mo-B alloy IC6

Abstract

A variety of experimental techniques have been used to study the effect of yttrium on the high temperature cyclic oxidation behavior of a directionally solidified (DS) Ni-Al-Mo-B alloy IC6. The cyclic oxidation resistance of alloy IC6 is substantially improved by adding proper amount of yttrium, which is resulted from several beneficial roles played by yttrium. Yttrium decreases the harmful effect of sulfur to the adherence between the oxides scale and the substrate, and the depth of the diffusion layer by inhibiting cationic transportation. Yttrium promotes the selective oxidation of aluminum and decreases the proportion of NiO region in the surface oxide scale. Yttrium migrates to the oxide grain boundaries and promotes the formation of a fine close packed oxide grain structure, and hence improves the mechanical strength of the grain boundaries.