Morphological characterisation, tribological behaviour and corrosion resistance of GTAW and SMAW welded lean duplex stainless steel S32101

This study evaluates the effect of welding process and heat input on the microstructure, tribological behaviour, and corrosion performance of lean duplex stainless steel (S32101). The material was welded using gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) with ER2209 filler. Two heat inputs were used: 0.85 kJ/mm (low) and 1.3 kJ/mm (high). Optical and SEM analyses confirmed duplex microstructures with balanced phase fractions. Ferrite reached about 55.9% in low-heat GTAW, while austenite reached about 52.7% in high-heat GTAW. No intermetallic phases were detected. Localised EDS measurements indicated relative enrichment of alloying elements in GTAW weld metal, with increases of about 12% Cr and ∼79% Ni compared to the base material. Mechanical and surface performance were assessed using impact, microhardness, and constant-load scratch tests (5–20 N). Low-heat GTAW weldments showed higher hardness, narrower scratch tracks, and lower frictional response than SMAW. Potentiodynamic polarisation in 3.5 wt.% NaCl revealed higher pitting potential and lower corrosion current density for GTAW welds. The findings indicate that microstructure modification by GTAW welding has a promising function in enhancing the mechanical performance and tribological features of S32101.