Transmission Electron Microscope Observations of SUS304L Stainless Steel Weld Metal

Abstract

Many previous studies have reported that various properties of stainless steel weld zone depend sensitively on the micro-structure. Generally the micro-structure is locally different in the weld zone. Therefore, in the present study the micro-structure distribution of SUS304L stainless steel weld zone by TIG arc welding was investigated mainly with a transmission electron microscope. In this paper, the observations of the weld metal are reported. The results are as follows:
(1) The ferrite content in the weld metal was higher at the surface region and lower at the fusion boundary region, while both Cr and Ni contents were nearly about constant all over the weld metal.
(2) The ferrite structure was acicular or Widmanstätten-like only in the surface layer and vermicular in the other region. The ferrite shape was roundish in the upper region and rectangular in the central region. The ferrite phases formed networks, or were connected each other by sub-boundaries.
(3) Cr and Ni contents, and Vickers hardness changed according to the ferrite structure distribution in the weld metal.