An experimental setup for the study of gas-solid reequilibration phenomena

The effect of Y additions on the oxidation mechanism of NiAl at 1270 K has been investigated. Mass transport in the alumina scale was examined with¹⁸O tracers. Proton activation analysis (¹⁸O(p, )¹⁵N) and SIMS were used to measure the¹⁸O distribution in the scale. On pure NiAl and low-doped (0.07% Y) NiAl mainly outward scale growth was observed. Addition of 0.5% Y induces oxide formation at both interfaces of the scale. Larger quantities of Y added to the alloy (>0.5%) do not dissolve completely in the NiAl, but form Y-rich segregates. Internal oxidation of these intergranular segregates was observed. The relation between the modification of the scale-growth mechanism and the improved adherence of the scale to the alloy due to the addition of Y is discussed.