Influence of the heat input and aging treatment on microstructure and mechanical properties of AISI 317 L steel weldments using 0020 robotic–pulsed GMAW

In this work, the effect of heat input and aging treatment on the microstructural characteristics and mechanical properties of similar AISI 317L austenitic stainless steel weldments used in the petroleum industry was investigated. The filler metal used was the AWS ER317L electrode at two different heat input levels (4 and 8 kJ/cm) in order to verify the influence of this parameter on the precipitation of deleterious phases. The specimens were aged at 700 °C for 50 and 100 h. Quantification and microchemical mapping of precipitated phases after welding and aging thermal treatment (ATT) were performed. Vickers hardness and tensile tests were used to evaluate the mechanical properties. It was observed that aging promoted a refinement of the base metal region, and all delta ferrite was transformed into sigma phase. The delta ferrite present in the fusion zone was completely transformed into sigma and chi phases. In the aged specimens for 100 h a lower occurrence of the secondary austenite phase (γ2) was identified, which indicates that with the increase of ATT time the dissolution of γ2 occurred in the already precipitated sigma phase. All welding conditions showed an increase in tensile strength, yield limit and hardness with the ATT.