Effects of metal atomization, arc and pressure fluctuations on the final particle size distribution in the wire arc spraying process

Summary form only given, as follows. In a wire arc spray process, an arc between tow wire tips melts the wire tips and a high velocity gas flow shears the molten metal of the tips and propels it towards a substrate. While the implementation of this process is relatively simple, the physical principles are very complicated and better understanding of them is required for improved process control and improved coating quality. In particular, a fundamental understanding of the mechanisms involved in metal atomization, arc jet interactions, along with the effects of system operating parameters on final particle sizes is needed to stimulate device innovations and system improvements. Three approaches will be presented to illustrate the physical mechanisms involved in this process. High-speed photography is used to view the arc and wire electrodes to identify the various melting and primary atomization mechanisms involved. Power spectrum analysis of arc voltage signal, i.e. arc fluctuations, and system sound signal, i.e. jet/arc pressure fluctuations, are used to identify intrinsic system frequencies at various system operating parameters. Characterization of the final particle sizes in the form of particle size distributions as well as characteristic average quantities are used to identify the effects of the system operating parameters, i.e arc current and gas flow rate. The above-mentioned studies are correlated to give a complete picture of the fundamental workings of the wire arc spray process.