Abstract

In cold gas dynamic spraying, the gas nature, process stagnation pressure and temperature, and the standoff distance are known to be important parameters that affect the deposition efficiency and coating quality. This investigation attempts to elucidate the effect of nozzle material on coatings produced using a downstream lateral injection cold spray system. Through experimentation, it is shown that the nozzle material has a substantial effect on deposition efficiency and particle velocity. It is proposed that the effects are related to complex interaction between the particles and the internal nozzle walls. The results obtained lead to the conclusion that during the particle/nozzle wall contact, a nozzle with higher thermal diffusivity transfers more heat to the particles. This heat transfer results in lower critical velocities and therefore higher deposition efficiencies, despite a noticeable reduction of particle velocities which is also attributed to particle-nozzle interactions.