Effects of mechanical vibration on microstructure of laser welded joint

The welding quality of welded joints can be improved effectively with vibratory welding process. To study the application of vibratory welding process on laser welding, 316 stainless steel is selected for the laser-vibration welding experiments. According to changing the vibration parameters and welding speeds, the microstructures of welded joints are observed with optical and scanning electron microscope, and are analyzed by contrast in different welding speeds and vibration frequencies. The results show that the columnar dendrites formed after welding are refined. The equiaxed dendrites in the center of weld bead and between the crystal axes are increasing. Meanwhile, the net-like σ-Fe and the dot-like carbides on the grain boundary of austenitic substrate are reduced and more diffuse with the mechanical vibration. In addition, microhardness test of the welded joints is conducted. The hardness of weld bead is higher with vibratory welding than that without vibration. It can also be found that the hardness is dramatically increased at a high resonance frequency. © 2015 Journal of Mechanical Engineering.