Experiments on the Creep Behavior of Semifinished X10NiCrAlTi 32 20 (Nicrofer 32 20) Tubes under Multiaxial Loading

摘要

For power plant components, the transferability of materials data from standard samples to the semifinished materials used for the installations was studied. To test transferability in the creep region for temperatures above 800 C, multiaxial creep tests were performed using tubes in a semifinished state. The results were compared with the results of uniaxial creep tests using standard samples. At 950 C microstructural changes occur in the tested material (X10NiCrAlTi 32 20, Nicrofer 32 20) which result in a creep behavior which can not be described directly by Norton's creep equation. There are significant differences in the creep behavior of the various product forms tested; tubes show significant creep hardening in the primary creep range and a delayed onset of the secondary creep range compared with bar material. Differences are caused by cold work introduced during straightening of the semifinished materials. In spite of the differences in the creep behavior, the transferability of materials data is possible, if a conservative method (reference stress of Treska, calculated from the highest stresses in the semifinished material) of stress calculation is used.