The Influence of Roughness and Two‐Step Process Parameters on the Oxidation Behavior of Aluminum Containing Austenitic Stainless Steel

The effects of roughness and two‐step process temperature on the growth of Al 2 O 3 film on Fe‐45Ni‐25Cr‐4Al based alumina forming austenitic (AFA) alloy under low oxygen pressure have been studied. Under oxidation process (850°C/5 h) of low‐temperature step of the two‐step process, a continuous Al 2 O 3 film forms on ground surface of AFA alloy, whereas a Cr 2 O 3 film develops on polished AFA alloy surfaces. The mechanism of forming Al 2 O 3 film on ground surface has been clarified. In addition, the high‐temperature step of the two‐step process critically promotes the growth of the protective Al 2 O 3 film. When the oxidation temperature is excessively high (1100°C), it causes wrinkled Al 2 O 3 film morphology, leading to film cracking and spallation. Conversely, insufficient oxidation temperature (900°C) leads to incomplete film coverage due to inadequate growth of the Al 2 O 3 film. The optimal oxidation temperature of 1000°C produces a continuous, dense, and well‐adhered Al 2 O 3 protective film. The influence of high temperature on oxide film growth morphology modification and internal stress has been analyzed.