Microstructure and wear-corrosion behavior of EH40 low-carbon steel coatings via underwater submerged arc cladding

In this study, a novel underwater submerged arc welding cladding (USAC) technique was employed to fabricate a well-formed cladding layer without significant defects on EH40 low-carbon steel, and a systematic comparison with underwater wet arc cladding (UWAC) was conducted to elucidate the evolution of microstructure as well as the variations in wear and corrosion behavior among the materials. The USAC cladding exhibits a dense surface and good formation quality. Benefiting from the thermal insulation of the slag wall, the microstructure is dominated by acicular ferrite. In contrast, the UWAC cladding experiences a higher cooling rate and mainly consists of bulk ferrite. The USAC cladding shows a smaller grain size, a higher dislocation density, and a larger fraction of low-angle grain boundaries, which leads to enhanced microhardness. The average friction coefficient of the USAC cladding is lower than those of the UWAC cladding and the base metal (BM), and narrower wear tracks with shallower grooves are observed. BM and UWAC were dominated by adhesive wear, while abrasive wear prevailed in USAC. Oxidative wear was partially observed in all samples. The USAC cladding exhibits a lower corrosion current density, and its corrosion morphology is dominated by uniform corrosion. The presence of acicular ferrite effectively reduces the corrosion rate. In contrast, the corroded surface of the UWAC cladding contains numerous inclusion-induced pits and residual impurities. Therefore, the USAC cladding technique enables the fabrication of cladding layers with good formability and excellent wear and corrosion resistance.