High Temperature Oxidation Behavior of Aluminide Coating Fabricated on UNS S30815 Stainless Steel

Aluminide coatings are widely used as a protective coating material due to their high corrosion and oxidation resistance properties. In this research, an aluminide coating was fabricated through aluminizing on UNS S30815 austenitic stainless steel using pack cementation method at 950 °C for 5 h. The isothermal oxidation was exerted on uncoated and aluminide coated steels for 200 h at 1050 ºC. Also cyclic oxidation was applied for 50 cycles at 1050 ºC on coated and uncoated steels. Surface morphology and cross section of coated and oxidized samples were characterized by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). X-Ray diffraction (XRD) was used to identify the formed phases in the surface layer of as-coated and oxidized specimens. As-coated UNS S30815 consisted of Al5Fe2, FeAl3 and Al2O3 phases. The results of the isothermal oxidation showed that the coated steel had lower weight gain (2.9 mg.cm-2) after 200 h of oxidation in comparison with uncoated one (7 mg.cm-2). Also the results of cyclic oxidation showed that the coated specimens had good resistance to thermal cycles.