Investigation of oxide scale formation and internal oxidation of an Fe-based coating at 500 °C and 600 °C

Abstract

In this study, we investigated an Fe-based coating that was produced on a cylindrical surface via an internal rotating plasma spray and was oxidized at different temperatures. For microstructural characterization, scanning electron microscopy and electron probe microanalysis were combined with energy dispersive X-ray spectroscopy and X-ray diffraction analyses. The Fe-based coating exhibits a dense structure with small amounts of internal oxides and pores after internal rotating plasma spraying. During the oxidation process, an iron oxide scale formed on the surface of the Fe-based coating, and the thickness of the oxide scale increased with increasing oxidation temperature and time. In addition, internal oxidation occurred in the alloy matrix and formed mixed oxides, mainly at the pores and the alloy particles' interface during the oxidation process. Compared to the Fe-based alloy, the oxidation behaviour of the Fe-based coating presented different results. The mechanisms of oxidation behaviour at different temperatures and time, including oxide scale formation and in-situ internal oxidation in the Fe-based coatings matrix, are discussed.