The Effect of Powder Composition on Cyclic Oxidation Behavior of CO-Deposited Al-Si Cating on Nickle-Based Superalloy

In this study, Si-modified aluminide coating on nickel-base superalloy IN-۷۳۸LC was prepared using a pack cementation method with various powder compositions at ۱۰۵۰ °C for ۶ h. The cyclic oxidation test was conducted at ۱۰۰۰ °C followed by cooling at room temperature for ۲۰۰ h and ۲۰ 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 ۲۹۳ and ۲۷۴ µm was achieved in the case of using pure Al and Si powder and alloyed Al-۲۰wt.%Si one in the packed mixture, respectively. It was also found that utilizing pure Al and Si powder with NH۴Cl 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.

Keywords:

Si-modified aluminide coating , Cyclic oxidation , Pack cementation , Superalloys