Surface engineering of Ni-Al coatings through concentrated solar heat treatment

Abstract

An improvement in the hardness, wear and corrosion resistance of a thermal-sprayed nickel-aluminium coating has been described in this paper, by using a post-deposition annealing treatment in a vertical concentrated solar radiation furnace at Plataforma Solar de Almeria, Spain. Annealing temperatures between 900 and 970 °C were used. It has been determined that the heat treatment leads to a 56% increase in hardness, 65% increase in scratch resistance and coating adhesion to the substrate, coupled with a 20% improvement in wear resistance, compared to the non-annealed reference. The improvement in mechanical properties has been related to increased heating gradient, formation of intermetallic NixAl compounds in the structure of coatings, as well as to a better compacting of coated assembly. The solar annealing treatment leads also to an improvement in the properties of coatings, with up to 87% in terms of corrosion resistance, and 20% in terms of wear resistance, comparing to the reference.