Effect of ultrasonic impact peening on TI-6AL-4V laser deposition shaping

Ti-6Al-4V is widely used in the aerospace industry, and the laser deposition shaping of Ti-6Al-4V is considered as an efficient method for manufacturing complex structural components. However, the components manufactured by laser deposition shaping face problems of distortion and cracking. In order to avoid these problems, ultrasonic impact peening was introduced into the Ti-6Al-4V laser deposition shaping process in this study. The effect of ultrasonic impact peening on microstructural modification, residual stress, specimen distortion, and microhardness of the laser deposition shaping specimen was studied. Experiments of laser deposition shaping were carried out with a 6 kW carbon dioxide laser and a coaxial powder feeder. The ultrasonic impact peening was processed after one bead of the Ti-6Al-4V laser deposition clad was accomplished. After mechanical polish, the microstructure of the ultrasonic impact peened specimen was observed using a scanning electron microscope. There was a grain refinement layer in the surface region of the clad with a depth of approximately 200 um. The residual stress of the specimen was measured by X-ray diffraction. The result of the residual stress measurement showed that the compressive residual stress of the specimen is introduced by the ultrasonic impact peening. The distortion of the specimen is measured using a three-coordinate measuring machine. Besides, inhibition of crack generation was achieved in the specimen processed by the ultrasonic impact peening. In conclusion, the ultrasonic impact peening is beneficial for the process of Ti-6Al-4V laser deposition shaping.