Tensile properties of friction welded AISI 4340 joints

Abstract Armor grade Q&T steels very similar to AISI 4340 are used for construction of combat vehicles due to its high hardness, high strength to weight ratio and excellent toughness. The influence of friction welding parameters on microstructure and mechanical properties of such armor steel friction weld joints were evaluated. The microstructural properties of the various weld joint regions were examined by optical microscopy. It was also observed that the fully deformation zone (FDZ), the partially deformation zone (PDZ) and the heat affected zone (HAZ) have a vital effect on the tensile strength of the welded joints. Nearly 83 % of the tensile strength of the parent material (PM) can be achieved in friction welded joints. This is a 17 % higher strength than with the same parent material welded by shielded metal arc welding (SMAW) and flux cored arc welding (FCAW). The respective tensile and impact properties of the welded joints were correlated with the weld metal microstructures and fracture morphologies.