Effect of Yttrium as Alloying Element on a Model Alumina-Forming Alloy Oxidation at 1100 A°C

In order to study the effect of yttrium as alloying element on the high-temperature oxidation of an alumina-forming alloy, 0.093 wt% yttrium was incorporated into a model FeCrAl alloy. Yttrium has a beneficial effect on the isothermal oxidation behavior in air at 1100 A degrees C. Glancing angle X-ray diffraction made on a sample oxidized for 1000 h under thermal cycling conditions indicated that yttrium is located at the internal interface as Y3Al5O12. Secondary neutral mass spectrometry results showed that the diffusion mechanism is modified by the presence of yttrium as an alloying element. Moreover, the beneficial effect of yttrium on the alloy oxidation is also related to a reduced metallic grain size. The growth of metal grains during oxidation was especially observed on the yttrium-free FeCrAl alloy. It is also well established that the diffusion mechanism in the oxide scale is modified by yttrium. The aim of the present work was to show that yttrium also plays a role on the aluminum diffusion in the metallic substrate and has a strong influence on the kinetic transient stage during the FeCrAl-0.1Y oxidation.