Title : Effects of Nitrogen (N?) shielding and purging gases on weld performance in austenitic stainless steels: An overview
Abstract:
Nitrogen (N?) is one of the alloying elements in austenitic stainless steels (ASS) and play an important role in various industries, especially oil and gas industries, since it enhances mechanical strength, corrosion resistance, austenite stabilization, and grain refinement. Nitrogen (N?) plays a dual role as a shielding and purging gas in ASS welding. Shielding gas is critical in protecting the molten weld pool from atmospheric contamination. Meanwhile, purging gas is applied to the underside of the weld bead, especially in processes like Gas Tungsten Arc Welding (GTAW) and Plasma Arc Welding (PAW), to prevent oxidation and contamination that can compromise corrosion resistance and mechanical performance. However, when N? is introduced excessively during ASS welding, particularly through shielding and purging gases, N? can contribute to weld defects such as porosity, nitride formation, and poor penetration. Besides N2, other common shielding gases for ASS welding include Argon (Ar), Helium, and mixtures of Ar with small amounts of oxygen or carbon dioxide. These gases ensure a stable arc, regulate heat input, and prevent oxidation, thereby contributing to weld integrity. Among them, Ar is the most widely used shielding and purging gas due to its inert nature and ability to produce consistent and high-quality welds. While Ar remains the preferred shielding and purging gas, N? is sometimes used as a cost-effective alternative, improving mechanical properties and enhancing corrosion resistance. However, as mentioned earlier, excessive N? incorporation may lead to detrimental effects, particularly porosity and nitride precipitation, which can weaken the weld. Hence, its effect on weld quality varies depending on welding parameters and material type. Notice that the limited review study gathers and summarizes the existing studies on shielding and purging gases using N2 compared to Ar as shielding and purging gases for the ASS welding processes. To address this research gap, this review study aims to provide a more comprehensive study on the effects of shielding and purging gases using N2 compared to Ar in influencing ASS weld quality.
