A Comparative Study of High Temperature Tensile and Creep Testing Between Standard and Miniature Specimens: Applicability and Limits

Abstract

This study concerns the quasi-static and time-dependent mechanical behavior obtained via the miniaturized electro-thermal mechanical testing (ETMT) approach for single crystal (SX) and conventional cast Mar-M-247 superalloy. The experimental outcome was benchmarked against standardized testing procedures. It is found that tensile yielding behavior can be captured accurately by the ETMT approach up to 1100 ^{circ }C, provided the appropriate type of thermocouple (T/C) is chosen. Furthermore, creep rupture behavior is underestimated by the miniaturized set-up. High repeatability of the rupture time was obtained for the SX case, whereas a significant scatter was observed for the conventional cast case. The discrepancies are assessed in detail; discussion centers around analytical and practical considerations, such as temperature uncertainty due to parasitic voltage and the choice of T/C, microstructural change as a result of the Joule heating, representative gauge volume, and strain rate non-linearity. Consequently, the applicability and limits of the miniaturized approach are examined critically, and improvements were suggested where appropriate.