Arc-welded armour steel: A tailored and comparative study of its microstructure and mechanical properties

Abstract

The present research aims to investigate and analyse the metallurgical features, including macrostructure, microstructure, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and electron backscatter diffraction. In addition, the mechanical properties of the arc welding specimens, encompassing hardness, tensile properties, and impact toughness at room temperature, were determined. The specimens were joined utilising various welding techniques, including gas tungsten arc welding, gas metal arc welding, shielded metal arc welding, and flux-cored arc welding. According to macrography, the weldments have no porosity, inclusions, or penetration. This confirms the optimal weldment fabrication process parameters. An optical microstructure analysis was conducted on various zones of the weldments. The weld fusion zone's microstructure reveals delta (δ) ferrite within the austenite matrix. A two-phase microstructure of bainite and untempered martensite is observed in the heat-affected zone. Scanning electron microscopy images at higher magnification reveal austenite and partially δ-ferrite phases. Energy-dispersive X-ray spectroscopy analysis showed higher chromium, nickel, manganese, silicon, and molybdenum concentrations on the grain boundary than in the matrix. According to electron backscatter diffraction, the average weld zone grain sizes for gas tungsten arc welding, gas metal arc welding, shielded metal arc welding, and flux-cored arc welding are 21.4, 35.8, 25.8, and 34.3 µm, respectively. In the heat-affected zone, the grain size decreased significantly. The welding region has lower mechanical properties than the heat-affected zone. All specimens produced using different welding processes had no cracking in the weld metal, including the fusion zone and border.