The effects of peak temperature and cooling rate on the susceptibility to intergranular corrosion of alloy 690 by laser beam and gas tungsten arc welding

This study investigates the effects of welding method, peak temperature, and cooling rate on the susceptibility to intergranular corrosion of alloy 690 weldments. The experimental results reveal that the laser beam welding process with cooling rate of around 212.6 °C/s can be produced with much less mass loss and a lower value of maximum reactivation current density/maximum anodic current density than with the gas tungsten arc welding process, where cooling rate is at around 17-20.6 °C/s. This is because the very rapid cooling rate during welding leads to an insufficient exposure time of around 2.1 s within the chromium (Cr)-carbide precipitation temperature range, suppressing Cr-carbide precipitation and Cr-depletion along grain boundaries in the weld decay region of the heat affected zone.