Effect of gas temperature and nozzle traverse speed on the deposition efficiency in cold spraying
V.S. Shikalov, S.V. Klinkov, V.F. Kosarev
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: cold spraying, surface activation, critical nozzle traverse speed
Abstract
The influence of the stagnation temperature of the accelerating gas flow and that of nozzle travel speed on the deposition efficiency are studied when depositing single Cu-coating tracks by the cold spray technique. The experiments performed clearly show that the nozzle traverse speed substantially affects the value of measured deposition efficiency: the higher is the nozzle traverse speed, the lesser the measured deposition efficiency turns out to be at all other things being identical. Such a behavior can be explained by the fact that the first impacts of particles onto the substrate do not lead to their adhering to the surface and, hence, to coating deposition. It is known that, before the coating starts to grow, it is necessary for the substrate surface to be subjected to a sufficient number of particle impacts. This preparatory stage is called the activation stage, or the delay (induction) stage of the deposition process. It is shown for the first time that the specific (per unit area) mass of the powder consumed at the activation stage depends on the stagnation temperature of the accelerating gas flow: the higher is the stagnation temperature, the lower is the specific mass consumed.
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