Comparison of microstructure and oxidation behavior of CoNiCrAlY coatings produced by APS, SSAPS, D-gun, HVOF and CGDS techniques

MCrAlY coatings are widely preferred in materials used at high temperature applications exposed to oxidation and hot corrosion. The coating process used in the production of thermal spray coatings directly affects the microstructure and lifetime of the coating. In this study, a CoNiCrAlY metallic bond coat was deposited on Inconel 718 superalloy substrate material using APS, SSAPS, D-gun, HVOF and CGDS spraying techniques. The produced coatings were subjected to isothermal oxidation tests at 1000 °C for different exposure times. Porosity, surface roughness, XRD, SEM, EDX-elemental mapping analysis were used to investigate and determine the microstructures and the changes in the dimensions of thermally grown oxide (TGO) layer as a function of time and temperature. The obtained data were compared before and after the oxidation tests, and the findings were evaluated considering other related studies within the literature. The results show that CGDS CoNiCrAlY coatings exhibited better oxidation resistance than the coatings produced by the other techniques.