Evaluation of the Adhesion and Slurry Wear Erosion of Nb₂O₅ Coatings Applied by Flame Spray

Niobium pentoxide (Nb₂O₅) has excellent chemical and thermodynamic stabilities, characteristics that have accelerated the applications of this material in the form of coatings to protect against corrosive processes. However, few studies have evaluated its performance in wear protection applications. In this research, the slurry wear erosion resistance of Nb₂O₅ coatings deposited by flame spray was studied. The microstructural characterization of the coatings was performed by optical microscopy and scanning electron microscopy (SEM) assisted by chemical analysis by energy dispersive X-ray spectroscopy (EDS). Adhesion of the coatings was determined by the adhesion test (ASTM C633-13). Image analysis was used for the quantitative study of the adhesion tested areas and porosity of the coatings. Erosive wear resistance was determined using a container tribometer with erosive mixing at a particle velocity of 9.33 m/s and two particle incidence angles. The thinner coatings had fewer microstructural defects, such as pores and microcracks, and greater adhesive strength. The thicker coatings presented a cohesive failure mode. When the impact angle of the erodent particles was 90 deg, the thickness of the Nb₂O₅ coatings should not exceed 350 μm. Nb₂O₅ coatings applied by flame spray showed good resistance to slurry wear erosion, besides inherent low cost and flexibility of the process.