Microstructure and corrosive-wear resistance of surfacing layers for underwater wet welding

Abstract

Underwater wet welding (UWW) is a widely employed method for underwater welding. In this study, Ts306 electrodes were utilized for surfacing on Q235 base material by UWW, and the microstructure and corrosive-wear resistance of the surfacing layers were studied. The results demonstrate that the UWW presents thicker surfacing layer compared with that welded in air, due to the compressive effect of the water on the arc. Meanwhile, the microstructure of the UWW surfacing layer is closely related to the welding current. When the current reached 120 A, the structure of the surfacing layer was mainly pearlite and ferrite. The microstructures of grain boundary ferrite (GBF), acicular ferrite (AF), ferrite with second phase arrangement (FSP), and proeutectoid ferrite (PF) began to exhibit as the current increased to 135 A. When the welding current reached 150 A, the proportion of AF content experienced an increase. The microstructure of the surfacing layer can be refined, leading to an obvious increase in microhardness and corrosive-wear resistance. The substantial increase in the microhardness of the surface layer by 32% and the significant enhancement in corrosive-wear resistance by 60% were observed. Furthermore, the transition of corrosive-wear mechanisms from fatigue wear, corrosion wear, and oxidation wear to abrasive wear, oxidation wear, and adhesive wear was noted.