A Study of the Effect of Ultrasonic Assistance on the Microstructure and Corrosion Resistance of Laser-Welded P110 Steel

Corrosion failure in welded joints is a critical issue that affects pipeline safety in the oil and gas industry. This study comparatively examines the differences in microstructure and corrosion resistance of P110 casing steel-welded joints prepared using two processes: ultrasonic-assisted laser welding (UA-LW) and laser welding (LW). The results indicate that ultrasonic vibration significantly influences the microstructure and corrosion resistance of the weld zone in P110 steel, while having a limited effect on the properties of the heat-affected zone (HAZ). The application of ultrasonic vibration to the weld zone refines the grain structure and inhibits martensite formation. Ultrasonic vibration treatment does not significantly affect the microhardness values in the weld zone (WZ) but improves the uniformity of the hardness distribution. In a CO₂-saturated solution, galvanic corrosion between the regions of the welded joint is not severe, irrespective of the presence of ultrasonics. When ultrasonic vibration is applied, the corrosion rates across the welded joints follow the order: HAZ < WZ < base material (BM). Additionally, ultrasonic vibration promotes the formation of dense corrosion products in the weld zone by refining the grain structure and enhancing the phase composition.