Application of Small Punch Tests for Screening of Mechanical Properties for T91 Steel

Abstract

The T91 steel is considered a perspective structural material for Generation IV (GEN IV) nuclear reactors components. The operating conditions of GEN IV nuclear reactor, which include higher operating temperatures, higher neutron fluencies and using liquid metals as coolants, constitute new challenges for structural materials validation. To properly assess the impact of radiation, thermal, load and environmental damage the screening test procedures for initial overview of the induced changes of mechanical properties need to be developed and validated. One of the test procedures with potential to be used for the mechanical properties screening is Small Punch test. Small Punch test receive considerable attention since their development in the 1980's. The use of miniaturized test specimen constitutes minimal requirements for the test material and the option of obtaining the test material directly from the component. They have been successfully used on industrial scale for design life extension of components for energy industry in the past. In this paper we address the issue of the Fracture Appearance Transition Temperature (FATT) determination by the means of Small Punch test for the T91 steel, manufactured according to ASTM standard A387-Ed99. The test specimen were manufactured and used for the experiments in a wide range of test temperatures. Multiple levels of deformation energy were used to provide more representative interpretation of the test data. A data fit is applied on the deformation energy – test temperature dependence to obtain the value of FATT from Small Punch test, which is subsequently correlated to the values obtained from testing sub-size Charpy specimens.