Combined effect and mechanism of thermal behaviour and flow characteristic on microstructure and mechanical property of oscillation laser-welded of IN718

Abstract

An oscillation laser beam was conducted to enhance the mechanical property of Inconel 718 joints. The dynamic behaviours of molten pool on the microstructure and mechanical property of joints were investigated. The results showed that the improvement of Laves phase and the tensile property depended on the flow and thermal behaviours of molten pool. Compared with conventional laser welding, the maximum flow velocity on the surface of molten pool increased by 375.5%(150 Hz), which indicated the dendrites received greater bending stress to break more easily, resulting in the homogenisation of element. In addition, the oscillation laser beam decreased the temperature gradient from 218.5°C/mm to 73°C/mm, and the cooling rate of 150 Hz in the centre and edge of molten pool increased by 64.4% and 111.9%, which hindered the segregation phenomenon during the element diffusion to restrain the formation of Laves phase in the eutectic reaction.

The characteristics of dynamic stability in aluminium alloy keyhole weld pool flow

“…These characteristics play a crucial role in accurately assessing the welding state [9]. It is widely recognised that the flow of material during VPPAW determines the weld's condition [10]. Hence, establishing a correlation mechanism between weld pool flow and effective characteristics is of paramount importance.…”

Investigation of keyhole behaviour and its impact on the performance of laser beam oscillating welding through imaging and acoustic signal analysis

“…Based on the results of the aforementioned process experiments, some researchers utilised process monitoring information to investigate the dynamic evolution of keyholes and molten pools in LBOW, which are used for validation in finite element analysis [10], or to explain the weld performance such as Yan et al [11] studied the flow velocity trend of the molten pool in the LBOW process of IN-718 alloy using high-speed imaging and found that the fluid flow velocity was highest at a oscillation frequency of 150 Hz, resulting in more effective scouring of dendrites. These studies often showcase individual images with distinctive features, and the sensors used are typically limited and have low sampling frequencies, which cannot provide a comprehensive characterisation of the welding process.…”