Ignacio Aviles Santillana
CERN, Switzerland
Title: Fracture toughness of austenitic stainless steel welds for ultra-high vacuum and cryogenic applications
Biography
Biography: Ignacio Aviles Santillana
Abstract
Austenitic stainless steels have been used extensively for very low temperature applications due to their high strength and ductility, ready weldability, high fracture toughness and a low fatigue crack growth rate down to cryogenic temperatures. Today stainless steels are also the dominant materials of ultra-high vacuum (UHV) constructions. For the most demanding applications, a high temperature vacuum firing treatment is applied to the finished components in order to reduce the outgassing rate. Vacuum firing, for some specific applications, might be carried out within the range of sensitization temperatures for the steel. For this reason, it is essential to assess the impact of such heat treatments on the ductility and fracture mechanics properties of stainless steels, which are particularly relevant for components to be used in the cryogenic range.
The present paper investigate mechanical and fracture toughness behavior at 4 K of AISI 316L and AISI 316LN tungsten inert gas (TIG) welds using an austenitic stainless steel filler (EN 1.4453). Additionally, the effect on fracture toughness of two typical vacuum firing treatments (950 ℃ for 2 hours and 650 ℃ for 24 hours) is evaluated. A correlation between the evolution of properties and microstructure as resulting from the above treatment is provided.