Oxidation and Corrosion Evaluation of β‑NiAl Coatings Deposited onto Pure Nickel and Superalloy Substrates.

Thermal barrier coatings (TBCs) play a crucial role in protecting aeroengine turbine blades in high-temperature environments. An essential component in these multilayer systems is the bond coat, which guarantees the adhesion of the ceramic topcoat and superalloys. This study employs a high-activity pack aluminizing method to form a coating. This was followed by the assessment of corrosion and oxidation behavior of β-NiAl coating formed onto pure nickel and CMSX-4 single-crystal superalloy substrates. In addition, the substrates without coatings were also subjected to both corrosion and oxidation tests. Thus, several characterization techniques are carried out to study the microstructures, phases, corrosion, and oxidation resistance of the substrate materials and their corresponding coatings. Electrochemical tests exhibited a high corrosion rate of pure nickel substrates with and without β-NiAl coatings in comparison with the CMSX-4 superalloy counterpart. Oxidation tests at 1150 °C for 50 h in open air were carried out. The β-NiAl coatings of all substrates showed better oxidation resistance than those of the substrates. In comparison, pure nickel samples exhibited poor oxidation resistance compared to their CMSX-4 counterparts. Therefore, in general, β-NiAl coatings improve oxidation resistance; however, they may compromise corrosion performance, depending on their substrate material.