SUBSTRATE AND FEEDSTOCK FACTORS AFFECTING COLD SPRAY COATING ADHESION AND RELATED IMPACTS ON CORROSION

Abstract

Cold spray technology has the potential to greatly reduce the effects of corrosion on susceptible materials. Lack of adhesion strength is one of the limitations currently preventing cold spray from becoming a dominant resource. Adhesion strength is the strength of the bond between the cold-sprayed coating and the substrate. Without good adhesion, the coating provides minimal protection against corrosion and could potentially make corrosion worse. In order to determine how to increase cold spray adhesion, the feedstock powder and substrate were manipulated to analyze their effects on adhesion. The main areas of focus for this project were the effects of the following characteristics on adhesion strength: i) the surface condition of the substrate, ii) the hardness of the substrate, and iii) the size of the cold spray particles. Samples within each area of focus were sprayed using cold spray and then a pull-off adhesion test was performed. The surface condition of the substrate was further studied to determine its effect on Mg AZ31 alloy’s corrosion rate by placing a smooth, roughened, and polished sample within a salt fog chamber for 672 hrs. The results from the adhesion tests showed that softer substrates and smoother surface condition produce higher adhesive strength. The corrosion experiments found that the samples with the higher roughness value saw the highest corrosion rates and formed the thickest oxide layer.