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

Abstract

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.