Comparison of CoNiCrAlY Bond Coats Deposited Through SSAPS And D-Gun Techniques

Abstract

In high-temperature environments where oxidation and corrosion are major concerns, MCrAlY coatings have become the preferred choice due to their exceptional properties. These coatings consist of a ceramic topcoat and a metallic bond coat, applied using various coating processes, to provide a protective barrier between the substrate and topcoat. The bond coat, particularly rich in CoNiCrAlY, offers excellent resistance to oxidation and corrosion. Various studies found that how thermal spray coatings are produced (Thermal Spray Method) greatly impacts both the structure and durability of the coating throughout its lifespan. This study focuses on investigating the application of a CoNiCrAlY metallic bond coat on an Inconel 718 superalloy substrate using SSAPS and D-Gun spraying techniques. The coated materials underwent isothermal oxidation tests at 1000°C for durations of 5, 25, and 50 hours. Microstructural analyses, such as porosity, surface roughness, XRD, and SEM, were conducted to assess the bond coats oxidation behaviour and thermally grown oxide (TGO) layer's dimensions over time and temperature to assess oxide growth behaviour. Comparing the pre- and post-oxidation test data and drawing insights from relevant literature, the study found that the SSAPS-produced CoNiCrAlY coatings exhibited superior oxidation resistance compared to those created using the D-Gun technique. Furthermore, electrochemical corrosion tests in a 3.5 wt% NaCl solution revealed that the SSAPS-deposited coating displayed a lower corrosion rate and stronger corrosion resistance compared to the D-Gun-deposited coating.