Effect of synchronous induction heating on residual stress for laser-based directed energy deposition of thin-walled structures

To reduce the high residual stress during directed energy deposition (DED), induction heating is always integrated. However, traditional pre-heating method has limits to applied in some important fields like repairing and hybrid manufacturing. Synchronous induction-assisted laser deposition (SILD) is a new technology, which have great potential to in-situ control the thermal stress flexibly. Nevertheless, the complex dynamic deposition process resulting from two heat sources complicates the understanding of the underlying mechanism for the generation of residual stress in SILD. This study established a 3D finite-element model based on the indirect coupling thermo-mechanical method to investigate the stress behavior during SILD. The experimental and simulation results were in good agreement and confirmed that the integration of synchronous induction heating significantly reduced the thermal stress during the deposition process, but increased the temperature gradient and thus thermal stress in the cool-down phase. The residual stress of the finished SILD-fabricated part is determined by these two competing mechanisms. As a result, the distribution of residual stress is counterintuitive. Although the maximum residual stress is reduced, residual stress in some part increased with the integration of synchronous induction heating. This study will provide new insight for the in-situ reduction of residual stress in DED.