Abstract
Cold spray process is a low temperature spraying method (<600°C) based on particle high kinetic energy at impact (velocity in the range 300-1200 m/s). Powder is injected in a specific designed nozzle and, there, reaches high velocity. Even if bounding mechanisms are not perfectly known, it is established that adhesion can’t exist below a definite particle velocity called critical velocity. This specific velocity depends on both powder and substrate characteristics (chemical composition, mechanical properties…). The large number of parameters makes the determination of critical velocity very complex. But it is a fundamental value to determine the correct operating conditions. This work presents an imaging technique that allows a fast measurement of critical velocity. In this paper, the measuring method is first validated by comparing the critical velocity of copper (sprayed on copper substrate) found in the literature, with the measured one. Its accuracy is then tested with other materials and, finally, some improvements of the method are proposed.
