CRYOGENIC INVESTIGATIONS ON CYCLIC PROPERTIES OF TYPE 316LN AND INCOLOY 908 ALLOYS FOR SUPERCONDUCTING MAGNET APPLICATIONS

摘要

Within the framework of the European fusion development program the cyclic behavior of structural materials foreseen for the design of large size superconducting (SC) magnet systems, necessary for hot plasma confinement are investigated at cryogenic temperatures. Within this context the candidate jacket materials used for the SC-cable are extensively studied with respect to their fatigue crack growth rate (FCGR) and fatigue life properties at 7 K. These materials were Type 316LN austenitic high strength, high toughness materials and a nickel base super alloy designated as Incoloy 908. The manufacturing route of the SC-cable jacket is hot tube extrusion in long lengths of 5 to 7 meters with subsequent orbital welding process. Different type and size of specimens machined from the extruded jacket's square cross section (51 mm × 51 mm) having a central bore of 38 mm ○ were used as the basis for the tests conducted at cryogenic temperature.