Thermo-Mechanical Coupling of Corner Structures in Laser Directed Energy Deposition

ZHU Xiaochen; GU Heng; GAO Xuehao; QIAN Lili; REN Xudong

doi:10.16490/j.cnki.issn.1001-3660.2026.12.011

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Surface Technology ›› 2026, Vol. 55 ›› Issue (12) : 155-171. DOI: 10.16490/j.cnki.issn.1001-3660.2026.12.011

Laser Surface Modification Technology

Thermo-Mechanical Coupling of Corner Structures in Laser Directed Energy Deposition

ZHU Xiaochen^1a, GU Heng^1a*, GAO Xuehao^2*, QIAN Lili^1b, REN Xudong^1a

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Abstract

Laser directed energy deposition (LDED) offers high flexibility and efficiency, enabling rapid fabrication of large components in small batches as well as surface enhancement and repair and has become an advanced technology for surface structure design and remanufacturing. Complex geometries mainly include cross-shaped, ring/columnar, S-shaped, and polygonal structures. Corner structures are the fundamental elements of these complex geometries. Overfilling is a key challenge in manufacturing of corner structures. In addition to causing geometric deviations, excessive heat accumulation in corner zones increases the risk of stress concentration and distortion.
To investigate the relationships between corner angle, deposition velocity, and the temperature and stress fields, numerical simulations were combined with experiments. Under constant laser power, powder feed rate and stand-off distance, corner angles of 15°, 30°, 45°, 60°, 90°, 120°, 150°, and 180° and deposition velocities of 10, 15, 20, and 25 mm/s, the geometric structures were examined. Since deposition velocity changed the molten pool size and thus the geometry of the deposited layer, separate finite element mesh models were established for the four deposition velocities, with a uniform element size of 0.3 mm in the deposited layer. Both powder and substrate materials were 316L stainless steel. Straight-line deposition at 180° was used for parameter calibration and model validation.
By analyzing peak temperature, cooling-stage temperature, cooling-stage temperature gradient, temperature change rate, and equivalent residual stress at different locations of corner structures, the effects of secondary laser scanning and corner geometry on the temperature and stress fields were clarified. The results showed that corner angle significantly affected heat accumulation and residual stress. Smaller angles (e.g., 15°) intensified heat accumulation and increased temperature gradients and cooling rates, which markedly raised residual stress. When the corner angle exceeded 90°, the temperature and stress distributions approached those of straight-line deposition, and the angle effect weakened. Deposition velocity affected the temperature and stress fields in a nonlinear manner. In the low-velocity (10-15 mm/s) and medium-velocity (15-20 mm/s) ranges, temperature and residual stress varied strongly with velocity. Changes were smaller at velocity speed (20-25 mm/s), although excessively high velocities might increase residual stress. The relationship between residual stress and deposition velocity was non-monotonic. In this work, a medium deposition velocity helped reduce stress concentration.
During low-velocity deposition at 10 mm/s for a small-angle (15°) corner structure, local remelting occurs within the corner zone, which releases thermal stress. As a result, the residual stress in the remelted region (241 MPa) is reduced by 27.4% compared with that at the boundary upon leaving the corner zone (322 MPa). As the corner angle increases, the location of maximum residual stress shifts from concentration at the corner boundary to a more uniform distribution. At the interface between the deposited layer and the substrate, residual stress mainly concentrates at the outer corner, inner corner, and the start and end of deposition. Residual stress at the outer corner is higher than that at the inner corner, and the end position shows higher residual stress than the start position.
Corner angle and deposition velocity are the primary factors governing thermal stress evolution, and laser remelting provides an effective means for regulating residual stress. These findings provide a theoretical basis for process optimization and residual stress control in laser directed energy deposition of complex path features.

Key words

laser directed energy deposition / corner angle / deposition velocity / temperature field / stress field / numerical simulation

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ZHU Xiaochen, GU Heng, GAO Xuehao, QIAN Lili, REN Xudong. Thermo-Mechanical Coupling of Corner Structures in Laser Directed Energy Deposition[J]. Surface Technology. 2026, 55(12): 155-171

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Funding

Strategic Priority Research Program of the Chinese Academy of Sciences (XDB0910000); National Natural Science Foundation of China (52205370, 52206252)