Particle-at-impact parameters in Cold Spray are governed mostly by gas flow parameters. However, the location of the powder injection can be used as independent factor to modify particle-in-flight parameters. Calculations and experiments confirm strong influence of the location of the powder injection on dynamics of particle acceleration and heating. Application of this effect for cold spraying of multicomponent coatings is a new and promising approach. The general scheme of spraying of two-component mixture composed of hard-sprayable and easy-sprayable components proposed as follows: The hard-sprayable component is injected into the subsonic part of the nozzle at a gas stagnation temperature favorable for this material to start the coating formation alone. The zone of injection of the easy-sprayable component is determined in such a way that the particles of this material have, at the nozzle outlet, values of temperature and velocity sufficient for the coating formation at the selected gas stagnation temperature. New design of spraying nozzle for the above purposes is proposed and discussed.

This paper presents some results of investigation of the cold spraying various composites including metal-ceramics, metal-metal with a new nozzle design. The objective of this study was to develop a nozzle with an ejector that allows the injection of powder components in different points of the gas flow that can provide optimal spray parameters for each component. For this purpose the installation was equipped with three feeders and three powder feed ports. The first one was located in a pre-chamber (high pressure powder feeder) and two others were located in the ejector in supersonic part of the nozzle. Varying the powder injection location of any component allowed us to change the spray parameters of the mixture. Some preliminary spray results of different powder mixtures are presented to illustrate possibilities of such approach. It is shown that an addition of ceramic or metal powder to the sprayed metal can significantly change the spray process and coating characteristics