Tribological Behavior and Residual Stresses of Gas Tungsten Arc Welded Dissimilar Joint of sDSS 2507/X-70 Pipeline Steel

The present study investigates the tribological behavior and residual stresses of sDSS 2507/X-70 dissimilar weld joints, focusing on their structural integrity for marine applications. Gas tungsten arc welding was performed using ER2594 and ER309L filler metals at lower heat input (LHI-0.7 kJ/mm) and higher heat input (HHI-1.4 kJ/mm). Utilizing a slurry pot tester with varying silica sand concentrations (10 and 30 wt pct), weight loss, erosion wear, and wear mechanisms are analyzed in marine environment. The investigation provides a comprehensive understanding of erosive behaviors by analyzing surface and microstructure characteristics using scanning electron microscopy. All specimens experienced significant weight loss in response to increasing slurry concentrations. Weight loss increased by 17 pct for sDSS 2507 base metal (BM) and 36 pct for X-70 BM with increased slurry concentration. High slurry concentrations induce significant weight loss due to sand particle density, particle-to-surface contact, particle interactions, and fluid impacts. ER309L-LHI lost 55 pct more weight than ER2594-LHI in response to increased slurry concentration, while ER309L-HHI lost 56 pct more weight than ER2594-HHI. Compared to both BM, ER2594-LHI and ER309L-LHI exhibit superior resistance to slurry erosion. ER2594-LHI and ER309L-LHI erosion rates increased 1.14 and 1.32 times with slurry concentration. Material removal mechanisms included micro-cutting, crater formation, lip fragmentation, and ridge formation. Deep-hole drilling method has been used to estimate the residual stress in the weld zone. ER2594 weldment exhibited predominantly tensile residual stress distributed throughout its thickness. The weld surface experienced a longitudinal residual tensile stress of 241 MPa, with the lowest residual stress observed at the weld root. In the ER309L weldment, the maximum residual stress recorded was 175 MPa. The study recommends suitable welding parameters in terms of heat input and filler metals (ER2594 and ER309L) for improved slurry erosion resistance in sDSS 2507/X-70 welds, highlighting the significance of residual stress analysis to evaluate weld structural integrity under operational conditions.