Effect of Y on Oxidation Behavior of Directionally Solidified Ni-Based Single-Crystal Superalloy

The effect of yttrium (Y) addition on the oxidation behavior of a Ni-based directionally solidified single-crystal superalloy is investigated in this study. Isothermal oxidation tests for samples with different levels of Y addition are conducted at 1100 °C in air. The Y content of the samples is determined by the actual pickup amount obtained from an Inductively Coupled Plasma-Atomic Emission Spectrometry test. It is discovered that the addition of Y increases the oxide resistance by the scale of an adhesive double-layer oxide, which is composed of Al 2 O 3 and spinel Ni(Cr,Al) 2 O 4 . With 70 ppm of Y addition, the oxidation mass gain decreases from 12.6 g/m 2 for the alloy without Y addition to 5.3 g/m 2 , and the oxidation rate decreases significantly. In addition, the internal nitride disappears after Y doping because of an increase in oxidation scale adherence and a decrease in oxidation products. In this study, the alloy with 660 ppm Y addition demonstrates the best oxidation resistance.