Difference between helium retention properties in 316L and 304 stainless steels

The difference between helium behavior in type 316L and 304 stainless steels at high temperature was examined. Thermal desorption experiments were performed to obtain fundamental knowledge on the retention properties of helium atoms and in situ TEM observation was also carried out to examine the related dynamic behavior of helium bubbles. The desorption properties indicated that SUS316L has strong retention up to high temperatures. In SUS316L, a large desorption peak was present at temperatures above 1200 K, whereas most of the retained helium was desorbed at comparatively low temperatures in SUS304. In situ TEM observation consistently showed rather lower mobility of bubbles in SUS316L compared with SUS304. The suppression of bubble motion could be caused by Mo atoms, the additive in SUS316L.