Type-I hot corrosion behavior of Cr-modified slurry aluminide coating superalloy Rene 80

In this study, the structure and type-I hot corrosion behavior of chromium-modified slurry aluminide coatings obtained by chromizing/Cr-plating before the slurry aluminizing have been discussed. Microstructural and elemental/phase analyses showed that the modified coatings contain a high-aluminum NiAl phase with chromium concentrated on the top-coat zone in the form of Cr-enriched deposits in comparison to the simple aluminide coating. The chromium content was decreased with the distance from the top layer of the coating, although a high concentration of chromium was observed within the interdiffusion layer which is routine for aluminide coatings. The furnace hot corrosion test of Na₂SO₄-deposited coated specimens of the modified coatings as well as the simple aluminide coating was conducted at 900 °C for 70 h. The coatings, corrosion products, and attacked areas were studied after 10, 30 and 70 h intervals. The chromium-plated slurry aluminide coating with 57 at% Al and 31 at% Cr in its top layer showed the best type-I hot corrosion resistance.