| Two-wire arc spraying is an inexpensive thermal deposition process in which the materials to be deposited are introduced into the plasma as wires in the form of consumable arc electrodes. A cold gas jet across the arc atomizes and drives the molten particles from the electrode tips towards a substrate, thus forming the deposited film. Arc spraying is used widely to coat engineering structures in order to protect them against corrosion and wear. The coatings structures and properties such as porosity, hardness, adhesive bond strength and wear resistance and fume generation are strongly affected by the processing parameters which include arc voltage, gas pressure, gas velocity, particle size, particle velocity and nozzle shape etc.. The focus of this study is on the investigation and optimization of the two-wire arc spray process through an understanding of the interaction between process parameters and coating microstructure and properties.; Combination of plasma diagnostic techniques and materials characterization has been very successfully employed to investigate correlations between process conditions and coating quality. Converging-diverging nozzles, secondary gas atomization, and non-reactive gas atomization have been successfully developed to improve coating properties. The effect of arc fluctuations, gas velocity, particle size and particle velocity on coating porosity, hardness, oxide content and elemental loss has been determined. The effect of secondary gas atomization on adhesion and wear resistance has been investigated and adhesion and wear mechanisms have been postulated. |
