Investigation of microstructure, hardness, and electrochemical properties: The effects of N2 addition on the welding of duplex stainless steel (DSS)

Duplex stainless steel (DSS) is known for its superior strength, corrosion resistance, and good weldability, primarily due to its equal proportions of ferrite and austenite. However, during welding, the balance between these phases can be disrupted. This study aims to investigate how the TIG welding process affects microstructural deterioration and precipitation formation in DSS weldments. The changes in microstructure have been assessed by evaluating tribological properties and corrosion resistance. The investigation focused on the type of shielding gas used during welding at a constant flow rate of 10 L/min. The welding current and welding speed were 170 A and 175 mm/min, respectively. The corrosion resistance of DSS weldments was determined using three electrochemical techniques: linear polarization resistance, electrochemical impedance, and potentiodynamic polarization. The results indicated that using 100% argon as the shielding gas reduces the austenite volume fraction to 47% without causing precipitation. This reduction results in increased hardness up to 350 HV, although there is a slight decrease in corrosion resistance with a corrosion penetration rate CPR of 0.02 mm/year. Conversely, when using a shielding gas containing 20% nitrogen and argon, there is a slight increase in the austenite phase up to 57% with the appearance of Cr 2 N precipitation, leading to a decrease in both hardness and corrosion resistance below 300 HV and 0.03 mm/year, respectively.