Diffusion Aluminide Coatings for Hot Corrosion and Oxidation Protection of Nickel-Based Superalloys: Effect of Fluoride-Based Activator Salts

The influence of two different fluoride-based activator salts (NH4F and AlF3) was studied for diffusion aluminide coatings obtained via pack cementation on a Ni-based superalloy (René 108DS). resistance to oxidation hot corrosion assessed as function the concentration used during synthesis process by means cementation. Two concentrations were selected (respecting equimolarity fluoride in synthesis) compared terms morphology, thickness composition, well microstructural evolution after high temperature exposure. Isothermal tests conducted at 1050 °C air 100 h tubular furnace. kinetics evaluated measuring weight variation with exposure time. induced investigated SEM microscopy, EDS analysis X-ray diffraction. Results showed that AlF3 salt are thicker than those using NH4F consequence growth mechanism pack-cementation. Despite this evidence, it found show better resistance, both total mass gain quality microstructure thermally grown oxide. On other hand, produced exhibited conditions, showing negligible variations 200 aggressive NaCl Na2SO4 salts.