Nanopowder deposition by supersonic rectangular jet impingement

With a view toward developing the next generation of coatings using nanopowders, a cold gas dynamic spray (CGDS) technique has been investigated. In this method, a powder feeder is used to inject nanopowder agglomerates into a supersonic rectangular jet, with a design Mach number of 3.2. The powder particles gain speeds of up to 700 m/s through momentum transfer from the jet and bond to the substrate surface due to kinetic energy dissipation. Coatings of copper and nano-WC/10% Co on steel and aluminum substrates (3 to 5 µm in thickness) have been produced. The benefit of this process is that the material does not undergo any chemical changes during coating formation. To improve the quality of the coatings produced, the flapping motions produced by supersonic jet impingement were studied. Powder particle velocities and the jet impingement flow field were quantified using particle image velocimetry (PIV).