The Microstructure and Pitting Resistance of 2002 Lean Duplex Stainless Steel after the Simulated Welding Thermal Cycle Process

Abstract

In this paper, thermal cycles with different heat inputs and cooling rates were investigated for a novel lean duplex stainless steel 2002 using a welding simulation. The microstructure and pitting resistance of the simulated heat-affected zones were studied. With the increasing heat input, the amount and size of the austenite phase both increased, along with a transformation from rods to dendritic structures. The critical pitting temperature (CPT) and the pitting potential (Epit) both increased first and then declined as the heat input increased, indicating a strong dependence of pitting resistance on the heat input. For the different cooling rates, the amount of ferrite increased as the cooling rate increased from 0.25 °C/s to 20 °C/s. The CPT and Epit both increased with the increasing cooling rates, indicating an improved pitting resistance. The pits initiated preferentially at the boundaries of ferrite and austenite due to the precipitation of M23C6 in the specimens with different cooling rates.