Effect of Substrate Heating on Corrosion Behavior of Nickel Coated on AISI 1020 Steel by Cold Gas Dynamic Spraying

In cold spraying, formation and adhesion of the coating is mainly due to the kinetic impact of the powders as they impinge on the substrate, at velocities above the critical value, causing substantial plastic deformation of both the particles and substrate. Most of the research around cold spraying focuses on preheating the gas before spraying; however, this article is aimed at preheating the substrate only and evaluating its effect on the microstructure of the coating. Before deposition the substrate was preheated at different temperatures to understand its effect on the corrosion behavior. The analysis shows that the powder particle could efficiently deposit, by increasing the substrate temperature up to at least 250 °C. The corrosion current density extracted from the Tafel plot shows a decreasing trend than bare 1020 steel in 3.5 wt.% NaCl solution. However, at higher temperatures the corrosion behavior detriments due to an increase in the oxygen content of the coating during deposition. An estimation of the gas velocity shows that substrate heating is beneficial in obtaining high deposition efficiencies even with low gas velocities, much below the theoretical critical velocity for nickel.