Investigation of mechanical, microstructure, and corrosion properties of duplex stainless steel joint for natural gas processing facilities

Abstract

Duplex stainless steel is an exotic material known for its excellent corrosion resistance and mechanical properties due to the presence of a two-phase structure that is quite balanced between ferrite and austenite, making it one of the top choices for the oil and gas industry. In this paper, we will discuss the process and investigation of the welding results of the A/SA 790 UNS 31803 duplex pipe joint which is connected using the gas tungsten arc welding (GTAW) process for gas purification process applications. The welding process and qualification is based on the ASME BPVC Sec code. IX was then tested to obtain information on the characteristics of the mechanical properties, microstructure, and corrosion resistance of the resulting joints. Heat input in the welding process is a crucial factor that determines the equilibrium of the ferrite and austenite phases which then correlates with the mechanical properties and corrosion resistance of the joint. Based on the microstructural analysis, there was a decrease in the ferrite phase in the weld metal, but it was still within the required limits. Furthermore, the results of the mechanical properties test showed that the tensile strength of the joint was greater than the tensile strength of the base metal and no open discontinuity was observed in the bending test. The corrosion test showed no signs of pitting corrosion with a weight loss value of 1.7 g/m2.