Particle sedimentation in cored-wire-arc directed energy deposition: Particle migration and suppression mechanism via ultrasonic vibration

Cored-wire-arc directed energy deposition (DED), as an emerging manufacturing technology, can achieve multi-material additive manufacturing and satisfy the demand for structural-functional integration. However, high-density particles will sink and aggregate at the bottom of molten pool, which will cause defects such as cracks or porosity, decreasing the bonding between the deposited layers and deteriorating the mechanical properties of the components. Therefore, it is essential to investigate the migration behavior of particles in molten pool and the suppression strategy to improve formation quality. Here, a three-dimensional numerical model is developed to reveal the molten pool dynamics and particles migration mechanism during cored-wire-arc DED. The influence of molten droplets impingement and molten pool flow on particles migration behavior in the additive manufacturing process is investigated. Furthermore, the effect regulation of relative velocity between particle and molten pool on particles migration behavior is analyzed mechanistically, which reveals the sedimentation mechanism of the particles. Results demonstrate that molten pool flow velocity will influence the relative velocity between particles and molten pool, which will decide the acceleration of particles; moreover, the particles will sink while the relative velocity is in the same direction with gravity or the relative velocity is lower. Finally, ultrasonic vibration (UV) is introduced to suppress the sedimentation and aggregation of particles, and the corresponding suppression mechanism is revealed. UV will increase the flow velocity of molten pool, which will suppress the sedimentation and agglomeration of particles, as well as reduce the temperature gradient of molten pool, increasing the depth of penetration. This work provides a foundation for further improving the quality of components fabricated via cored-wire-arc DED.