Impact of Zirconium Addition on the Adhesion Strength and Tensile Fracture Mechanisms of Flame-Sprayed AlCoCrFeMo High Entropy Alloy Coatings

In thermal spraying, the performance and service life of a coating are primarily determined by its adhesion strength to the substrate. In this study, flame spraying was employed to deposit high entropy alloy (HEA) coatings of AlCoCrFeMo-Zrₓ (x = 5, 10, 15 wt.%) onto 316L stainless steel. The addition of Zr as dispersoids was intended to promote the formation of Al₃Zr precipitates, which are expected to enhance the embrittlement resistance of the coatings. The adhesion properties and tensile fracture mechanisms of the coatings with varying Zr wt.% were investigated for potential use in embrittlement repair applications. The coating microstructure was characterized using scanning electron microscopy (SEM), and phase formation was analyzed using X-ray diffraction (XRD). Microhardness testing and ASTM Standard C-633 testing for adhesion or cohesive strength were performed on the flame-sprayed coatings. Coating characterization indicated an increase in Al₃Zr formation with higher Zr wt.% in the feedstock powder. The results indicated that coating hardness influenced adhesion strength, thereby enhancing resistance to plastic deformation under loading. Furthermore, the formation of ZrO₂ within the coatings positively affected coating hardness. The adhesive strength of the splat particles was significantly influenced by the presence of oxides within the coating.