Steam oxidation of scratched β‐FeAl coatings on P92 steel

Abstract

AbstractAluminizing is a low‐cost and effective technology to improve the oxidation resistance of P92 steel without impacting its mechanical properties. In that regard, it is worth investigating whether a defective coating has an effect on oxidation. A modified aluminizing method is developed to form a thin β‐FeAl layer on heat‐resistant P92 steel under relatively lower temperatures. And the steam oxidation behavior of scratched β‐FeAl coating, scratch‐free β‐FeAl coating, and P92 steel is investigated in this study. The results exhibit that an unstable Fe‐rich oxide layer with a thickness of more than 130 µm grew on the P92 steel, while only an extremely thin α‐Al2O3 scale of less than 0.2 µm emerged on the aluminized‐P92 steel and a bi‐layer nodules oxide scale formed on the scratched aluminide coating. However, the steam oxidation resistance of the coating with a scratched track is still better than that of the steel substrate but far less than that of the scratch‐free coating. To maintain optimal oxidation resistance, the scratched area should be repaired by the formation of a fresh aluminide coating.