Evolution of residual stress and microstructure of 2205 duplex stainless steel welded joints during different post-weld heat treatment

Abstract

Duplex stainless steel (DSS) has been widely used in various applications due to the combination of excellent mechanical properties and corrosion resistance. However, shielded manual arc welding (SMAW) always deteriorates its phase balance and further changes its mechanical properties. Therefore, an appropriate post-weld heat treatment (PWHT) is of the essence to gain the superior performance of the DSS SMAW joint. In this article, the effects of PWHT temperature on the microstructure and residual stress of 2205 DSS SMAW joint were investigated by both experimental and simulation methods. The microstructural characteristics including phase ratio, morphology, grain misorientation, and boundary type were analyzed by the electron backscattered diffraction, while the evolution of residual stress was investigated by a thermal–mechanical coupled finite-element simulation and hole drilling method. The results showed that the residual stress decreased significantly after PWHT, particularly under the higher PWHT temperature. The maximum longitudinal residual stress had dropped by 20.4 and 66.8% at the PWHT temperatures 380 and 1,050°C, which were both far below the yield strength. However, the increase in PWHT temperature promoted the phase proportion imbalance due to the excessive precipitation of intragranular austenite and the formation of low-angle grain boundaries. The fraction of austenite had reached 75.5% when the PWHT temperature was 1,050°C. In order to obtain a reasonable distribution of residual stress and microstructure for the 2205 DSS SMAW joint, it is recommended to perform PWHT at 380°C.

Keywords

• duplex stainless steel
• shielded manual arc welding
• residual stress
• microstructure
• post-weld heat treatment