Analysis of mechanical and tribocorrosion properties of thermally sprayed Nb2O5 coatings

Niobium and its alloys have been used for several industrial applications including high strength and low alloy steels in the automotive and aerospace industries mainly because of being highly corrosion resistant in different media. Niobium pentoxide, for being chemically inert to corrosive agents that cause severe corrosion and is normally present in refineries and other industrial environments, is an excellent option to reduce costs in repairing damages caused by corrosion, protection of industrial equipment or industrial systems. Whatever the application, mechanical properties and adhesion of coatings to substrates define their effective durability and performance, mainly for tribocorrosion applications. In this work, these properties are studied and correlated for Nb2O5 coatings applied by HVOF and LVOF spraying onto steels. Substrate roughness and coating thickness was varied to verify the influence in the adhesion as well as in the wear and corrosion performance. Electrochemical impedance spectroscopy, adhesion (ASTM C633-01), abrasive wear resistance (ASTM G65-03) and SEM microstructural analysis allowed the evaluation and comparison of the coatings.