Cold Spray MCrAlY Coatings on Single-Crystal Superalloy Using Nitrogen: Properties and Economics

Abstract

Cold spray (CS) has been proven a promising manufacturing process for the MCrAlY coatings deposition. In this study, NiCoCrAlTaY coatings were deposited on single-crystal nickel-based superalloy (CMSX-4) substrates using the CS technique. Nitrogen and moderate spray parameters were used, and the resulting MCrAlY coatings were compared to coatings sprayed using helium under similar spray conditions. It was found that, contrary to general expectation, favorable coating characteristics were achieved when nitrogen was used. This is attributed to low deposition efficiency under the studied spray conditions, resulting in significant particle impingement that promotes overall particle deformation in the coatings sprayed using nitrogen. However, low deposition efficiency may lead to elevated process cost, despite great gas cost savings by using nitrogen, due to significant increases in powder waste and cost. As such, recycling of the non-deposited powder was explored in an aim to reduce powder cost when using nitrogen. A general cost model that considers the benefits of powder recycling was proposed for the CS process. It was demonstrated that the use of nitrogen and powder recycling can be economical over CS using helium, while producing MCrAlY coatings with desirable properties that are potentially beneficial to the oxidation performance of the coatings.