Spraying metal-ceramic coatings is a complicated task because, in addition to the spray parameters of the metal particles, it is necessary to take into account those of ceramics. This paper presents some results concerning the effect of the nature, particle size, and velocity of ceramics on the metal-ceramic coating properties. Copper and aluminium powders are used as metal components. Two fractions (fine and coarse) of aluminium oxide and silicon carbide are sprayed in the tests. Ceramic particle velocity is varied by the particle injection into different zones of the gas flow: in the subsonic (pre-chamber) and supersonic parts of the nozzle, and in the free jet after the nozzle exit. Simulation results and measurements of the particle velocity by the track method are compared. Influence of the ceramic particle parameters on the coating formation process and its properties is discussed.

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

Presently, the self-propagating high-temperature synthesis (SHS) has found wide use in the production of compacts and powder materials, and also in the fabrication of end products. Yet, a disadvantageous feature of the standard SHS process, which can be overcome in part by running the synthesis reaction under pressure, is that it fails to provide the possibility of obtaining high-density materials and products. It is therefore of interest to develop a combined process which would allow one to apply a two-component Ni-Al coating with prescribed stoichiometric composition by cold spraying of a nickel-aluminum powder mixture followed by self-propagating high-temperature synthesis of a target intermetallide (Ni3Al or NiAl) by treating the surface layer of the cold sprayed coating with a highly-concentrated energy flux (argon plasma jet). Preparation methods for nickel-aluminum powder mixtures (in particular, mechanochemical activation) intended for cold spraying process are discussed. Computational experiments were performed to substantiate the choice of stationary, traveling and pulsed energy sources for subsequent initiation of SHS in the heterogeneous layer deposited onto a steel substrate. A model was developed to predict the local phase state of the material synthesized in the coating; this model involves the state diagram of the Ni-Al system. The characteristics of sprayed coatings were examined. The developed approach is shown to offer much potential in practical applications.