Effect of Aluminizing on the High-Temperature Oxidation Behavior of an Alumina-Forming Austenitic Stainless Steel

Due to their excellent oxidation resistance and creep resistance at elevated temperature, alumina-forming austenitic (AFA) stainless steels have emerged as potential alloys for high-temperature applications. In this study, a reactive air aluminizing method was used to aluminize the surface of AFA 25 stainless steel. The high-temperature oxidation behavior of both as-received and aluminized AFA 25 was investigated at 850°C in dry air. The mass gain per unit area was higher for aluminized AFA 25 than for as-received material. X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive x-ray spectroscopy, performed on the oxide scales following high-temperature oxidation tests, confirmed 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.