In this study, Si-modified aluminide coating on nickel-base superalloy IN-738LC was prepared using a pack cementation method with various powder compositions at 1050 °C for 6 h. The cyclic oxidation test was conducted at 1000 °C followed by cooling at room temperature for 200 h and 20 cycles. The effect of powder composition and the way of cooling on the coatings microstructure and oxidation behavior were studied. Investigations carried out using a scanning electron microscope (SEM), EDS analysis, and XRD. Microstructural observations revealed that the coating thickness of 293 and 274 µm was achieved in the case of using pure Al and Si powder and alloyed Al-20wt.%Si one in the packed mixture, respectively. It was also found that utilizing pure Al and Si powder with NH4Cl as an activator in the pack led to the formation of silicide coating, owing to the higher diffusion of Si, which showed superior cyclic oxidation performance.
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1. By using the pure source of Al and Si, the coating exhibited enhanced cyclic oxidation resistance when compared to the alloyed source of Al and Si.
2. The coating thickness of the sample in the case of using NH4Cl as an activator was more than that of one prepared by AlCl3 as an activator.
3. Si increases the stability range of Al2O3 and improves the adhesion of the oxide layer.