Investigation on Aging-Induced Degradation of Impact Toughness and Corrosion Performance of Duplex Stainless Steel Weldment

Duplex stainless steels (DSSs) are prone to formation of various secondary phases in their microstructure upon exposure to high temperatures which can lead to degradation in their engineering performance. The present work was aimed to study the effect of a wide range of isothermal treatments (475°–1050 °C) on the impact toughness and corrosion resistance besides microstructure, ferrite content and microhardness of gas tungsten arc (GTA) welded 2205 DSS. It was observed that the isothermal exposure at 850 °C for 2 h led to maximum ferrite content reduction, imparted maximum hardening, caused maximum embrittlement of the weld metal (203 J → 2 J) and HAZ (204 J → 3 J) regions of the weldment besides causing maximum degradation in the pitting corrosion resistance. Corresponding to the aging condition of 475 °C/20 h, reduction in the ferrite content was not much, however, a significant increase in the microhardness along with severe loss in the toughness of the weld metal (203 J → 6 J) occurred, but the HAZ region was relatively tolerant (204 J → 54 J) against loss of toughness. In general, impact and corrosion properties were highly sensitive to degradation at 850 °C. Hence it can be inferred that the amount of ferrite content reduction cannot be directly correlated with the extent of hardening, decrease in the toughness and corrosion resistance; as such, changes will be primarily governed by the type of secondary precipitation which is temperature and exposure duration-dependent in the case of DSS welds.