Progress of Cryogenics and Isotopes Separation , ISSN: 1582-2575
2006, Volume 9, Issue 17+18

Mechanical and Structural Properties of Austenitic Stainless Steel Used in Nuclear Reactors. The Effect of Helium at Low Temperature

Abstract

An understanding of the behavior of He in metals is important because He is generated in the structural materials of fission reactors and future fusion reactors. Helium accumulation causes de`terioration of the material properties and may influence the useful lifetime of reactor components. It is well known that austenitic stainless steels, which will be utilized for nuclear components, with small amounts of helium, suffered severe embrittlement.

Two types of austenitic stainless steel were chose for investigation in order to determine the influence of corrosion factors, helium and internal defects, on the proprieties of materials at different temperatures.

The samples was cooled down at 20K and broken in order to observe the influence on the toughness. By X-ray diffraction analysis was determinate the concentration of the Feα% and Feγ%. The other components were induced by a corrosion treatment in diluted solution of HCl (18.3%) or HNO₃ (27.7%). The entire components obtain in the materials decrease strongly the toughness of the steels, with values comprises in 10-30%.

A surface mechanical treatment (work hardening) was made in order to modify the dislocation concentration. For these samples, we observed an increase of the toughness and mechanical resistance, in correlation with the increase value of the dislocation concentration.

The microstructural properties determined by X-ray diffraction analysis were compared with the mechanical tests results.