Investigation of the Surface Degradation Properties of Aluminized Super Austenitic Stainless Steel

Abstract

The intermetallic compounds formed on the surface of a substrate via the aluminizing process significantly affect its hardness and oxidation characteristics. In this study, 904L super austenitic stainless steel (904L) was exposed to pack-aluminizing via different parameters. The formed aluminide layer and its thickness changed depending on the process parameters. Complex phase constituents were observed according to XRD and SEM analysis, such as FeNiAl5, Fe4Al13 (FeAl3), FeAl2, and Fe2Al5. The aluminide phases increased the surface hardness by 4-5 times. In dry sliding wear tests, the increase in hardness caused by the aluminization process has been shown to reduce the volume losses of 904L by up to 85%. Moreover, the coefficient of friction was decreased owing to the aluminizing process, while the worn surfaces were smoother and slightly damaged. The 904L and aluminized samples were also exposed to isothermal oxidation tests at 1050 degrees C, in which 904L exhibited a double oxide layer composed of Cr2O3 and (Fe, Ni)Cr2O4, while aluminized samples predominantly comprised the alumina scale at the end of the tests. The formation of the alumina scale provided better protection and lower mass gain despite the occurrence of localized oxide delaminations.