Effect of the anti-seepage masking layer on the microstructure evolution of Ni-based superalloy during co-deposition of the Al-Si coating

This study optimizes turbine blade microstructures during production, specifically focusing on surface treatments for blade airfoils and dovetails. Blade airfoils need to prepare the Al-Si coating to improve oxidation resistance, while blade dovetails must prepare the anti-seepage masking layer to hinder the deposition and diffusion of active atoms into the substrate. The effect of the anti-seepage masking layer on the microstructure evolution of IN718 superalloys during co-deposition of the Al-Si coating was systematically revealed. Results indicate that by adding Si elements to modify the aluminide coating, a uniform and dense Al-Si coating was prepared on IN718 superalloys at 950 celcius for blade airfoils, enhancing oxidation resistance. Meanwhile, the anti-seepage masking layer with 42 gm could effectively prevent the deposition and diffusion of Al and Si atoms into the substrate for blade dovetails. Defects such as interface layers, micro-voids, and cracks between the masking layer and sub-strate facilitate the removal of the anti-seepage masking layer from the substrate after heat treatment. On the contrary, the thicker anti-seepage masking layer will induce the upward diffusion of Cr and Mo atoms and form a stronger metallurgical bonding with the substrate, which is difficult to remove and will harm the properties of the substrate.