<p>Thermal plasma spraying is used in various industries for component repair, corrosion protection, wear-resistance, or enhancing surface properties. Twin wire arc spraying (TWAS) is a plasma spraying process that offers low workpiece heating and high deposition rates at a lower cost. The TWAS process utilizes two electrically conductive wires. An electric arc is generated between the wires to produce molten droplets that are propelled towards a substrate to deposit a coating. Variations in TWAS process conditions cause the substrate temperature to fluctuate and even melt. Therefore, the motivation of this project was to simulate the heat transfer from the torch to the substrate during spraying and layer formation of a coating. Simulations using ANSYS FLUENT Computational Fluid Dynamics (CFD) software were used to model the heat transfer in a TWAS system. The simulations presented herein are representative of applied engineering practice rather than theoretical engineering research. To this end, the results of this paper are meant to augment and improve the database of TWAS technology. Prismatic inflation layers were used to simulate the thermal boundary layer at the stagnation point. The dynamic mesh was used to simulate how the growth of the coating influenced the temperature distribution across the film. To simulate the particle growth process, we employ the layering approach through the dynamic mesh option within ANSYS FLUENT. To do this we modeled the substrate and an additional fluid layer with a quadrilateral mesh pattern (as required to use the layering approach). We wrote a projection script and imported it into ANSYS FLUENT, this script is used to determine the growth of the substrate. Results for a heat transfer correlation (derived from the CFD simulation database) characterizing the substrate growth will be presented in the final paper.&nbsp;Using an ANSYS fluent software and its various features, we were able to determine how the TWAS process influenced the substrate surface. The results showed that for a 3 second time lapse, substrate surface temperatures reached 1050 °C. The model also showed the various temperature gradients across the fluid and solid zones.&nbsp;the energy generated by the impinging particles quickly increase the substrate surface temperature. At a standoff distance of 200 mm and for a 3 second simulation time lapse, the substrate surface temperature increased to 1050 °C. Since the substrate material is steel, it is understood how easily the substrate surface can be influenced to reach its melting temperature. &nbsp;The need to use a sweeping torch technique or a larger standoff distance is required to prevent the substrate surface from reaching its melting point within a relatively short time lapse.</p>

Multiphysics Modeling and Simulation of an Arc-Jet Sprayer

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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