Investigation on pyrometric temperature measurement and its correlation with WAAM bead profile

Abstract

Wire Arc Additive Manufacturing (WAAM) is a layer-by-layer method of manufacturing. It gained significant attention in industry and academia due to its potential to exploit the benefits for the production of components of intermediate complexity. The presented experimental study showcases the generated temperature behaviour during Gas Tungsten Arc Welding (GTAW) based WAAM. The effect of deposition parameters including wire feed speed, input current has been studied to determine the cooling rate and resultant bead properties for multilayer deposition. It was found that at constant current the change in wire feed speed yields an almost constant bead temperature. The cooling rate was found to be higher for the initial layer of deposition, reducing afterwards and further increasing and tends to saturate after significant layers of the deposition. It could be because the dominating mode of heat transfer for the initial layer is conduction, whereas convection and radiation dominate for further layers of deposition, thus the cooling rate decreases. Further increase in layer height enhances the side wall surface area which in turn increases the heat transfer convection and radiation hence an increase in cooling rate was observed. The simulation results performed in SolidWorks also confirm the same. Constant wire feed speed and variable current, mainly decreasing layer by layer, helped overcome undercut hence providing strength to the deposited product. This experimental study has ended up with a deposited multilayer of uniform height and thickness having an almost constant temperature by reducing layer-by-layer input power accordingly. The efficacy and suitability of the combination of wire feed and input power were studied, along with experiments and simulations for the mode of heat transfer and bead-dimensional behaviour. Keywords: WAAM, GTAW, Pyrometer, Temperature measurement, Heat transfer