Linear friction welding of T-Joints in low carbon steel: Effect of welding parameters on joint quality

Linear friction welding (LFW) is a well-established solid-state joining technique. However, its application in T-joint configurations remains unexplored. This study investigated the effects of welding parameters, such as oscillation direction, upset, and applied pressure after oscillation, on linear friction welded (LFWed) T-joints using low-carbon steel SM490A. The flash ejection behavior, flash profiles, microhardness, microstructure at the welding interface, and tensile properties of the joints were evaluated under various welding conditions. The results indicated that flash symmetry was lower along the oscillation direction and higher perpendicular to it. Short-side oscillation produced more homogeneous flash ejection compared to long-side oscillation. No distinct softening zones were observed in the hardness profiles of the LFWed T-joints. The microstructure at the welding interface consisted of martensite, bainite, and ferrite, indicating that the weld region reached temperatures above the A₁ temperature. The martensite fraction and hardness increased with higher upset and applied pressure after oscillation. Tensile tests revealed 100 % joint efficiency across all welding conditions, with ductile fracture occurring in the base metal due to the absence of welding defects and increased hardness at the interface.