Steam oxidation of scratched β‐FeAl coatings on P92 steel

Abstract

Aluminizing 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-Al 2 O 3 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.