High temperature oxidation behavior of low temperature aluminized Mirrax® ESR steel

Abstract

The aim of this study was to investigate the effect of aluminizing process on the oxidation resistance of mirrax steel. The oxidation behavior of pack cemented aluminizing coatings on Mirrax ESR Steel was investigated at 1000 degrees C for 5, 25 and 70 h. Low temperature aluminizing process was carried out at 700 degrees C for 2, 4 and 6 h by pack cementation method. The microstructures, surface morphologies and phase distribution of both coatings before and after oxidation were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and x-ray diffractometry (XRD). Analysis of the coating layer showed that the coating was homogeneous, non-porous and had a good bond at the interface of the coating-matrix. Coating layer was mainly composed of aluminum-rich Fe2Al5 phase. Depending on the increased process time, the coating thickness varied approximately from 17 to 58 microns. The aluminizing process could greatly improve the oxidation resistance of the substrate. Al diffused outward to form multi-layer oxide films, which prevented the diffusion of oxygen. A sticky, protective, non porous alumina film layer was obtained successfully. The results show that oxidation resistance increased with the increased aluminizing time.