Study of the high temperature oxidation performance of MCrAlY bond coats deposited by thermal spray and cold spray processes

Bond coats are an essential element in the aerospace industry, as they ensure the structural integrity and thermal efficiency of engines operating in extreme environments. The high-temperature oxidation performance of bond coats plays is an indicator of the durability and thermal resistance of thermal barrier coating (TBC) systems used in gas turbines. Several deposition methods have been used to deposit bond coats for TBCs, including high-velocity oxygen fuel (HVOF), high-velocity air fuel (HVAF) and cold spray (CS). These deposition methods significantly influence the microstructure and adhesion characteristics of the bond coats, which impact their resistance to high-temperature oxidation. The main objective of this study is to analyze how the deposition process affects the oxidation kinetics and the integrity of the oxide layer. To that end, a low temperature HVAF torch and a cold spray system are used to deposit MCrAlY coatings on a super alloy substrate. Isothermal oxidation tests are performed and the formation and evolution of the thermally grown oxide (TGO) layer is assessed. The microstructure of the coatings is assessed by scanning electron microscopy (SEM) and the oxidation is quantified on a field-emission scanning transmission electron microscope (FE-STEM) equipped with Energy Dispersive Spectroscopy (EDS).