Influence of deposition strategy on melt pool behavior and forming morphology of directed energy deposition-arc

In directed energy deposition-arc (DED-arc), the melt pool's thermodynamic behavior significantly impacts component morphology. Most existing studies focus on the influence of individual process parameters, with limited systematic investigation into the effects of key deposition strategies such as scanning strategy, interlayer cooling time, and deposition length. To address this, this study establishes a three-dimensional transient numerical model of DED-arc to systematically investigate how these strategies influence the melt pool's dynamics and formation characteristics. The results show that, increasing the interlayer cooling time from 0 s to 10 s significantly improves dimensional uniformity by approximately 19.7 %, achieved by decreasing the average deposition width by about 6.1 % and increasing the height by nearly 25.9 %. Furthermore, compared with unidirectional scanning, a bidirectional scanning strategy optimizes heat accumulation and enhances melt pool stability. Increasing the deposition length extends the stable formation zone, effectively mitigating the adverse impact of end instabilities on overall morphology. This study provides quantitative theoretical guidance for process optimization, parameter selection, and stable multi-layer formation in DED-arc.