Effect of Welding Input Parameters on Underwater Butt Welds in Saline Water Using Nickel-Coated Electrodes

Abstract

Underwater wet welding is widely used for marine repairs, but rapid cooling and hydrogen uptake often degrade weld quality by reducing toughness and increasing hardness. This study evaluates how welding parameters and nickel-modified rutile electrodes influence the mechanical performance of underwater SMAW welded butt joints in saline water. Commercial rutile electrodes and rutile electrodes containing 2.4 wt. % nickel were tested across welding currents (120–150 A), welding speeds (10–15 cm/min), and salinities (30–40 ppt). Mechanical performance was assessed by Charpy impact testing, tensile testing, and Vickers hardness measurements. Nickelmodified electrodes produced a marked improvement in impact toughness (nonnickel: 102–138 J; nickel: 135–158 J), a controlled reduction in weld bead hardness (nonnickel: 204–244 HV; nickel: 173–212 HV), and retained or improved tensile strength (525–571 N/mm² versus 501–530 N/mm² for nonnickel welds). Higher heat input (higher current, lower speed) further improved toughness by moderating cooling rates. The results indicate that nickel-modified rutile electrodes, combined with optimised welding parameters, offer a practical route to improve toughness and control hardness in underwater wet welds.