Effect of Build Height on Microstructure and Mechanical Properties of Hollow Tubes Fabricated Using Arc-DED Process

The current research effort employed the arc based directed energy deposition (DED) method to create high aspect ratio hollow tubes. The wire feed speed and travel speed of 1.5 m/min and 60 cm/min were chosen for final fabrication with an internal diameter and height of around 6 mm and 120 mm respectively. The properties were assessed in three different regions divided on the basis of build height designated as top, middle and bottom. The findings indicate a significant variation in mechanical properties caused by the presence of distinct microstructures. The superior mechanical properties were achieved in the bottom region, attributed to the grain refinement because of high cooling rate. The grain coarsening contradicts the highest hardness achieved in the top samples owing to the occurrence of brittle M/A islands in the microstructure. Additionally, the M/A islands transform into carbides inside the middle sample because of the elevated tempering temperature circumstances.