Synchronous non-contact ultrasonic-assisted laser deposition manufacturing of high-performance Inconel718 superalloy: microstructure and tensile properties

During laser deposition manufacturing (LDM) of Inconel 718 superalloy, the material undergoes rapid melting-solidification cycles that readily induce metallurgical defects and degrade mechanical properties. To address this issue, we propose a synchronous non-contact ultrasonic-assisted laser deposition manufacturing (SNU-LDM) process. A multi-field coupled model linking ultrasonic parameters, molten-pool behavior, and solidification microstructure was first established to reveal how the initial ultrasonic amplitude A 0 and excitation distance d (distance from the acoustic source to the molten pool) regulate acoustic pressure distribution, cavitation behavior, and temperature evolution. Simulations show that at A 0 = 3.5 μm and d = 20 mm, the maximum acoustic pressure reaches 1.193 MPa, significantly exceeding the cavitation threshold of 0.25 MPa. The cavitation-acoustic streaming synergy transforms the isotherms from a flat pattern into a comet-tail-ellipse shape, effectively modifying the solidification thermal field. Subsequent experiments with varying A 0 confirmed that increasing ultrasonic amplitude refines the average grain size from 211.45 μm to 140.47 μm and raises the kernel average misorientation (KAM) to 1.14°, indicating effective grain refinement and homogenization. Under optimized parameters ( A 0 = 3.5 μm, d = 20 mm), the tensile strength, yield strength, and elongation improved by 47.32%, 24.34%, and 49.31%, respectively, compared with the non-ultrasonic control specimen. Digital image correlation (DIC) strain analysis further reveals a more uniform strain distribution and reduced stress concentration. Mechanistic analysis attributes the property enhancement to the synergistic action of solid-solution, grain-boundary, and dislocation strengthening. The proposed SNU-LDM process provides a theoretical basis and practical processing window for fabricating LDM‑fabricated high-performance Inconel718 superalloy components.