Microstructural and Mechanical Property Analysis of High-Strength Low-Alloy Steel Tubes Fabricated Using Wire Arc-Directed Energy Deposition Technique

Wire arc-directed energy deposition advances complex part development,benefiting high-demand commercial applications, especially for parts with integratedcooling channels. Therefore, in the current study, hollow tubes with 6 mminternal diameter and 120 mm height were fabricated to analyse its mechanicalproperties along the build height. Various wire feed speeds and travel speeds wereused for fabrication, and mechanical properties were evaluated using miniaturetensile samples from the bottom, middle, and top regions of the part to determinelocalized strength. The results exhibited that the part fabricated at a wire feedspeed and travel speed of 1.5 m/min and 60 cm/min, respectively,showed superior mechanical properties. The materials characterization reveals agrain size increase of 57% in the bottom and 116% in the middle,compared to the top section. Grain refinement in the bottom and the presence ofmartensitic austenitic islands in the top regions led to increases in ultimatetensile strength by 21.5% and 8.6%, respectively, compared to themiddle section. The pole figure represents the strong texture in top regionsconsisting of equiaxed and columnar grains oriented parallel to the build direction.In addition, the remarkable reheating effects in the middle (74.4%) regionswere confirmed using grain orientation spread analysis. Consequently, these effectsled to the disintegration of martensitic austenitic islands into small-sizedcarbides, reducing the middle region’s hardness and strength. The top samplesshowed a significant distorted fraction (53.2%), possibly due to martensiticaustenitic islands confirmed by fractography analysis, with the highest hardness of302 ± 21 HV.