Microstructure evolution and mechanical properties of 316H weld metal during aging

A standard 316H welding wire was used to obtain 6% delta-ferrite in the weld metal by the automatic tungsten inert gas welding. The effect of aging time at 750 degrees C on microstructure and mechanical properties of the weld metal were analysed. The results showed that as the aging time increased, the delta-ferrite fraction decreased, and finally, delta-ferrite was no longer seen, the M23C6 fraction first increased and then decreased, and the sigma phase fraction increased. Finally, the fractions of M23C6 and sigma phase kept stable, but the size increased. Accordingly, as the aging time increased, the yield and tensile strengths first decreased significantly, then increased obviously and finally decreased slightly again, while the elongation and impact energy decreased all the time.