Correlation of microstructure and tensile properties of 316 stainless steel weld metal solution annealed at high temperatures

Abstract

The weld metal of AISI type 316 stainless steel, deposited by the gas tungsten arc welding process, was heat treated at 1323, 1373, and 1423 K. Study of the transformation kinetics showed that δ ferrite transformed to austenite at these aging temperatures. Optical microscopic studies of the weld metal showed that the amount of bferrite, its degree of inter connectivity, and its distribution decreased while the diameter/length ratio (d/l) increased, with increasing aging durations and temperatures. The austenite matrix evolved to reveal new recrystallised austenite grains on aging at 1423 Kfor 80 min. The results of tensile tests showed that the yield strength decreased while the ductility and work hardening exponent (n) increased with increasing aging times and temperatures. No significant change in ultimate tensile strength was observed. The changes in the amount, morphology, and distribution of δ ferrite did not influence the tensile properties. The weld metal aged at 1423 K for 80 min very nearly recovered to give properties similar to those of the base metal. Recovery and recrystallisation of austenite caused the observed changes in the weld metal tensile properties.