Tensile properties of welded helium-charged 304L stainless steel

The formation of helium in structural materials is a byproduct of both fission and fusion energy technologies. Helium may be produced by the transmutation of /sup 10/B, from the two step decomposition of /sup 59/Ni, by the implantation of energetic /sup 4/He particles or by tritium decay. Although it is chemically inert and essentially insoluble in the metal lattice, helium levels as low as 0.1 atomic ppm produced by irradiation have been shown to produce significant embrittlement at high temperatures. However, ambient temperature tensile data on heat-affected zone (HAZ) properties of helium containing stainless steels are scarce. Because welding of helium-containing stainless steels may be required in these structures, this study was performed to determine the effect of helium on the HAZ tensile properties of a Gas-Tungsten Arc (GTA) plate-on-plate weld in annealed 304L stainless steel. Helium-containing tensile specimens were prepared by thermally charging these samples with high pressure tritium, aging in a freezer to produce 526 atomic ppm of /sup 3/He, and thermally degassing the tritium at a low temperature. The samples were then exposed in a Gleeble /sup R/ machine to simulate HAZ thermal cycles which were based upon experimental measurements. Peak temperatures of 1073K, 1273K and 1473K were obtained by closed-loop temperature control, followed by ambient temperature tensile tests