An investigation on fracture toughness of the heat‐affected zone in the welded joints of 13% Cr‐4% Ni martensitic stainless steels

Abstract

Fracture behavior of the welded joints of 13% Cr‐4% Ni stainless steels deposited using multipass flux‐cored arc welding process was examined in both as‐welded and heat‐treated conditions, and JIc tests were performed. A crack starter notch was placed one millimeter far from the fusion line to evaluate the heat‐affected zone (HAZ). Unstable crack propagations toward the weld metal occurred during stable tearing for both as‐welded and heat‐treated HAZ. Only single‐point fracture toughness Ju values could be determined before fracture instability. The fracture toughness of the as‐welded HAZ was about 60% lower than that of the substrate steel but get significantly improved by heat‐treatment, reaching a value even slightly higher than that of the substrate steel. The fracture mode of the stable tearing was transformed from a mix of cleavage and dimpled rupture occurring by micro‐void coalescence mechanism for the as‐welded condition to a totally dimpled rupture in the case of the heat‐treated material.