Zirconium Gettering Effect of Stainless Steel in Sodium

Abstract

During the study of the stress-rupture properties of austenitic stainless steels in high-purity static liquid sodium, zirconium foil was placed in the sodium to getter oxygen and maintain a high-purity sodium environment throughout the test. Results of the biaxial stress-rupture tests on thin-walled Type-304 and Type-316 stainless-steel tubing in the range 1200°F (649°C) to 1400°F (760°C) showed that the rupture strength of the tubing was significantly lower in the zirconium-gettered static sodium than in non-gettered static sodium or helium. This reduction in rupture strength was greater with higher test temperature and longer exposure time. In the presence of sodium, the zirconium foil decarburized the stainless steel; the decarburization process also resulted in an extensive sigma-phase formation on the region of the tubing exposed to sodium. The decarburization increased with test temperature and time of exposure. It was concluded that the decreased stress-rupture strength of specimens tested in zirco...