Effect of Spray Parameters on MCrAlY In-Flight Particle Oxidation and Coating Microstructure Deposited by Internal Diameter High Velocity Air Fuel (ID-HVAF)

Aircraft gas turbine blades operate in aggressive, generally oxidizing, atmospheres. A solution to mitigate the degradation and improve the performance of such components is the deposition of thermal barrier coatings (TBCs). Specifically for bond coats in aerospace applications, the High Velocity Air Fuel (HVAF) process is very efficient for coating deposition. However, the internal diameter (ID) HVAF process has received little attention in the literature and could be a promising alternative to limit oxidation during spraying when compared to conventional methods. The main objective of this study is to analyze how the ID-HVAF process influences the microstructure and oxidation of MCrAlY coatings. To that end, an HVAF i7 torch is used to deposit MCrAlY coatings and splats on a steel substrate with different stand-off distances. Particle diagnosis tools such as DPV is used to measure the MCrAlY particle velocity, in order to analyze its influence on the shape and composition of the deposited particles. The microstructure is assessed by the study of the deposited splats and coatings through scanning electron microscopy (SEM) and the material oxidation is analyzed and quantified by both X-Ray Diffraction (XRD) and Energy Dispersive Spectroscopy (EDS).