Effect of mechanical vibration on the residual stress of direct laser metal deposition workpiece

Mechanical vibration with different frequencies was operated during the direct laser metal deposition process in order to discuss the effects of vibration on residual stress and other characters of deposited workpiece in this study. Sub-resonance, resonance and the optimum frequency (OPF) were selected for operation. The results revealed that the residual stress of the deposited workpiece was a tensile stress. With the operation of mechanical vibration, the stress of clad workpiece decreased, and the workpiece vibrated with the OPF showed the lowest residual stress. Microstructures of all the specimens with vibration refined, and the finest structure appeared in the specimen vibrated with the OPF. The hardness result showed that the lower the residual stress was, the lower the hardness was, and a low residual stress and hardness would have advantage of subsequent process of the deposited workpiece.