Simulated Stress-Induced Sensitization Study for the Heat-Affected Zone of the 304LN Stainless Steel Weld Using a Thermomechanical Simulator

Abstract

Stress-induced sensitization in the heat-affected zone (HAZ) of the 304LN austenitic stainless steel weld at 923 K (650 °C) was evaluated using a thermomechanical simulator (Gleeble 3800) at different stress levels. The simulated sensitization behavior of the HAZ was studied in close approximation of the stress and weld thermal cycle that is generally observed during pulse current gas metal arc welding of the 25-mm-thick section of the 304LN steel. The response to the degree of sensitization, as a function of the type and magnitude of stresses present in the matrix, was established through observations on changes in microstructure, electrochemical properties and hardness measurements. Transmission electron microscopy and selected area diffraction confirm that sensitization occurred and Cr23C6 precipitates formed at grain boundaries. The results indicate that the presence of tensile or compressive stresses, especially above the yield stress of the steel, enhances sensitization.