Formation characterization and dynamic mechanism of underwater wet wire and arc directed energy deposition

For the first time, the underwater wet wire and arc directed energy deposition (UW-WADED) multi-tracks deposition layers with favorable morphology were obtained. The forming characteristics of single-track UW-WADED were determined through response surface methodology. It was found that the power function curve provided the best fit for the profile of single-track UW-WADED owing to its changing plumpness value. Subsequently, the formation characteristics of multi-track UW-WADED with varying intervals were investigated. The deposition layer exhibited the flattest surface and the least root-mean-square deviation, measuring 321.79 μm when the interval was 8 mm. The dynamic process of UW-WADED was unveiled through X-ray high-speed images, leading to the formulation of UW-WADED droplet force model. As the arc bubble expanded, the horizontal component of the air drag force pointed to the opposite side of the molten pool and was the principal factor for the droplets to become spatters in UW-WADED. The mechanism of the defect formation was also revealed. The accumulation of the molten pool on the previous deposition layer coupled with the downflow of the molten slag were the inducers of slag inclusion defect while the exorbitant molten pool increased the likelihood of molten pool explosion and subsequent spatter formation.