Radiographic Characterization of Thermal Spray Jets Produced by Electrothermal Explosion of Ceramic Powders

Abstract

Thermal spray jets composed of Zr–B–O molten particles produced by the electrothermal explosion of a mixed powder of Zr and B2O3 were quantitatively characterized of their velocity, volumetric mass density, and mass velocity by flash radiography, to investigate a unique characteristic of a coating formed by using such jets, i.e., the mixing of a substrate material with a coating. Yttria-stabilized zirconia balls were used as tracers of jet flow. Mass velocity, i.e., mass flow rate per unit cross section of the flow, in a cylindrical space in front of the virtual position of a substrate was calculated using the velocity of the tracers and the volumetric mass density of the jet. The maximum mass velocity in the present spraying was two orders of magnitude larger than that in conventional plasma spraying. Thus, the very high mass velocity probably contributes to the appearance of the unique characteristic.