Adhesion Strength of HVOF Sprayed IN718 Coating

The adhesion strength of high velocity oxy-fuel thermally sprayed coatings is of prior importance when thick coatings are to be sprayed for aeronautical repair applications. In this study, relationships between process parameters, particle in-flight characteristics, residual stresses and adhesion strength have been explored. Design of Experiments (DoE) was utilized to identify the most important process parameters that influence coating adhesion strength. Residual stress distributions were determined using the Modified Layer Removal Method (MLRM) and adhesion strength was measured using an in-house developed tensile test. Relationships between process parameters, particle in-flight characteristics, coating microstructure and adhesion strength were established. Particle temperature, particle velocity, substrate preparation and deposition temperature were identified as critical parameters to attain high adhesion strength. Controlling these parameters can significantly improve the adhesion strength, thus enabling thick coatings to be sprayed for aeronautical repair applications