Determination of high temperature material properties of 15-15Ti steel by small specimen techniques: JRC technical report EERA JPNM Pilot project TASTE

This report presents the final results from the round robin test program on thin-walled cladding tubes in the EERA-JPNM pilot project TASTE. The test methods and assessment procedures used for the assessment of 15-15Ti steel are presented in a previous TASTE report 1. In this report the test results from different test types are assessed, compared and evaluated. The collation of results, mainly on tensile properties shows good agreement between tests methods. An open question remains if there is some anisotropy between the axial and the hoop direction of the tubes. Results from ring tension indicate lower strength values than the test performed in the axial direction. However, the ring tension calculated estimates do not take bending and friction into account. Tensile strength estimates from miniature Small punch tests samples (3 mm in diameter and 0.25 mm thick) indicate no anisotropy whereas tests on the full wall thickness (0.45 mm) with larger puncher balls indicate a reduction towards the INR measured tensile strength (Ring Tension) in the hoop direction. The ring compression test estimates based on calibration at room temperature by ENEA showed surprisingly good performance in estimating the tensile strength at higher temperatures despite the complex stress distribution for this type of test. The few tests performed for determining creep properties, i.e. small punch creep tests, were not successful in describing the expected creep properties. The SPC specimen (as was the case for some SP "tensile test") showed premature cracking at a very early stage of the test for the cold worked material. As a whole it seems that the different types of tests complement each other and together gives an overall picture of the strength and ductility of the tube material. The classical tests such as the ring compression test and the ring tension test gave good estimates on the hoop strength whereas the small punch tests seemingly give an estimate for the weaker direction.