As said before, cold spray using helium gas was implemented to
reach high deformation rates of powders particles. Calculations
performed using the KSS software indicate that a velocity in the
range of 700–800 m/s (depending on gun pressure) should be
obtained for particles of 30 mm in diameter. Thus, based on those
data calculated for copper particles, the ratio between expected
particles velocity and presumed critical velocity [23] should be
about 1.75. This value, situated in the middle of the deposition
windows for copper particles, is much higher than the one which
could be obtained using nitrogen gas (velocity of about 525 m/s
and ratio of about 1.15), yielding of course to higher deformation
rates upon impact. Under those circumstances, it is clear that the
little difference between the three alloys particle size distributions
is likely not to play a significant role in the process and therefore
should not hinder the comparisons between the three alloys.