Voltage and Current Fluctuations in Wire Arc Spraying as Indications for Coating Properties

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Abstract
Electric arc spraying with dual wires is an economical coating process finding diverse applications. Turbulence and velocity of an atomizing gas exert strong effects on the droplet formation and therefore on the coating properties. Turbulence intensity of an atomizing gas flow can be estimated by analysis of the waveforms of arc voltage fluctuations, and the velocity can be estimated by the frequency and the amplitude of these waveforms. Higher gas velocities result in higher frequencies and smaller amplitudes of the voltage fluctuations, and in smaller molten droplets leading to coatings with lower porosity but higher oxidation levels. Lower turbulence levels at the electrode tips result in more periodic waveforms with less high frequency content, and in lower oxidation of the coatings. Nozzle configurations such as a converging-diverging nozzle provide higher gas velocities with less turbulence leading to coatings with lower oxidation and lower porosity.

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