Interfacial TEM analysis of Cold Sprayed MCrAlY coating onto CMSX-4 Superalloy using Nitrogen

Cold Spray has been proven as a feasible process to deposit bond coats for thermal barrier coatings used on turbine blades. The deposition of MCrAlY coatings by this solid-state manufacturing technique has shown some promising alternative to other processes leave undesired. Even though the deposition of these coatings by cold spray has been made traditionally with helium (due to the larger speed that can be achieved), nitrogen has been explored in an effort to make the process more renewable and cost-effective. The lower velocity achieved by the particles when are sprayed using nitrogen raises the question of the bonding characteristic obtained by the deposition. In this study, the coating-substrate interface of the NiCoCrAlTaY coating sprayed with nitrogen onto CMSX-4 is analyzed using transmission electron microscopy. Different phenomena were seen, such as clear examples of metallic bonding, aggressive mechanical bonding, as well as some strain induced microstructural changes, e.g., recrystallization of the single crystal substrate.