Economic Potential of Cold Spraying MCrAlY Coatings: Use of Nitrogen and Feasibility of Powder Recycling

Cold gas dynamic spraying (CGDS or simply cold spray) has been proven a promising manufacturing process for the deposition of MCrAlY coatings for gas turbine applications. Helium is typically used in the process or nitrogen can be used if using elevated process parameters in an aim to achieve high particle velocities promoting coating formation. However, helium is considered as a non-renewable critical resource and is very costly; use of cost-effective gases such as nitrogen and powder recycling can be potentially economical. In this study, nitrogen was employed for the cold spray deposition of MCrAlY coatings using reduced spray parameters. Recycling of the non-deposited particles during the spray was explored, and the powder characteristics and cold sprayability of the recycled powder were compared with that of the as-received feedstock powder. The resulting MCrAlY coatings from the two powders, albeit with different coating thickness, show similar dense microstructure, low oxide inclusion, and reasonably smooth surface finish, which are considered as beneficial features that can improve the oxidation behavior of the MCrAlY coatings. The process cost of cold spraying MCrAlY coatings utilizing nitrogen, with and without the powder recycling, was analyzed and compared to similar processes employing helium as the process gas.