Microstructural, Mechanical, and Textural Evolution of Dissimilar Combination of Laser‐Welded Maraging Steel and 4340 Steel

Maraging steel, 4340 steel, and their dissimilar combination have similar applications in aerospace, defence, automobile and so on. This study examines and confirms the joint feasibility of their laser welding using mechanical testing, microstructural analysis, and texture analysis, thereby resulting in a sound dissimilar weld joint. The overall yield strength and tensile strength of the weld were increased by 14.4% and 16.67%, respectively, compared to those as‐received maraging steel. However, tensile strength improvement with reference to 4340 steel is 14%. Further, the elongation reached up to 19.7%, leading to a tougher weld joint. Vickers hardness has been determined to be 885 Vickers hardness number (VHN) and 650 VHN in heat‐affected zones (HAZs) on 4340 steel and maraging steel side respectively, which could be attributed to the formation of hard and needle‐like martensite. The presence of austenite was confirmed in the weld zone and HAZ of maraging steel according to X‐Ray diffraction (XRD) and Electron backscattered diffraction (EBSD) analyses, with a clear sign of reverted austenite. This resulted in local softening effect with a decrease in strength. Energy dispersive spectroscopy (EDS) analysis of the tensile fracture surfaces revealed the presence of TiO ₂ and Al ₂ O ₃ inclusions, which were also believed to be the cause of failure by acting as crack initiation points. Texture analysis of martensite phase proved the presence of ℇ‐ fiber, γ‐fiber, and partial presence of α‐fiber in as‐received maraging steel. Additionally, their intensities became lower in the weld zone and HAZ due to phase transformation of both martensite and reverted austenite phases induced by weld thermal cycles.