Investigation of Al<sub>2</sub>O<sub>3</sub>-Modified Aluminide on 304SS: Microstructural Evolution, Hardness and Growth Kinetic through Slurry Aluminizing

The microstructure and growth kinetic of alumina (Al 2 O 3 )-modified aluminide coating were investigated at 650°C, 680°C, and 700°C for various durations (4, 6, 8, and 10 hours) using the slurry aluminizing process. The heat-treated samples were analyzed through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) to assess microstructural evolution, elemental composition, and phases of the coating. SEM observations revealed a two-layer aluminide coating, comprising an Al-rich intermetallic (FeAl 3 ) and a Fe-rich intermetallic (FeAl). Microhardness tests showed that FeAl 3 had hardness values ranging from 880 to 990 HV, while FeAl, with values between 610 and 700 HV. The growth kinetics indicated that the thickness of the aluminide layers increased with both the aluminizing temperature and time, following a parabolic growth law. The activation energy for the growth of FeAl was 343.15 kJ/mol.