Abstract: The particles velocity and atomizing characteristics of droplets in high velocity arc spray (HVAS) and regular arc spray processes are investigated respectively. Both atomizing gas flow velocity and particle flying velocity are measured by a dual rotating disk technique and pitot tube method respectively. The particle size distribution under various are sprayed processes is investigated by use of a scanning electron microscope and an image analyzer. Statistical tests for their particle size distributions are carried out according to Pearsonχ{sup}2 distribution test method. Results show that the axial gas flow velocity of HVAS fluctuated ranging from 550m/s to 700m/s at the primary atomizing zone, i. e. spray distance within 100 mm. The average particle velocities of high velocity are sprayed aluminum and chromium alloy steel reached 342m/s and 388m/s respectively, which are in excess of the local velocity of sound. Both HVAS and regular are sprayed aluminum’s particle size followed Poisson distribution. However high velocity arc sprayed chromium steel had different particle size distribution from that of regular arc. The influence factors on particle velocity and atomizing mechanism of HVAS process are also discussed on the basis of above experimental results and analyzing of gas flow velocity field.

Key words: Atomizing mechanism, High velocity arc spray, Particle size distribution, Particle velocity, energy-absorbing features, evolvement mechanism, polyhedron sandwich structure, regular polyhedron unit-cell