PNNL

Abstract

Due to their excellent oxidation resistance and creep resistance at elevated temperatures, alumina forming austenitic (AFA) stainless steels have emerged as potential alloys for high temperature applications. In this study, a Reactive Air Aluminizing (RAA) method was used to aluminize the surface of AFA25 stainless steel. The high temperature oxidation behavior of both as-received and aluminized AFA25 was investigated at 850 °C in dry air. The mass gain per unit area was higher for the aluminized AFA25 than for the as-received material. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), performed on the oxide scales following the high temperature oxidation tests, confirmed the formation of alumina scale on both as-received and aluminized AFA. However, the aluminized alloy exhibited a thicker alumina scale on the surface, as well as more extensive penetration of the scale into the subsurface region of the alloy.