Creep Rupture of Pressurized Alloy 617 Tubes [report]

Jill Wright, Richard wright
2013 unpublished
Creep behavior of Alloy 617 under multi-axial loading has been characterized at 950°C using thin walled tubes with internal gas pressure. Tubes were machined from Alloy 617 plate material to ensure comparability of material properties with extensive testing carried out in the VHTR Research and Development program. Properties of this alloy under multi-axial loading are of interest for elevated temperature design in advanced nuclear heat transfer systems. A constitutive model in the form of a
more » ... n the form of a Norton relationship was developed for Alloy 617 plate to allow development of a suitable creep specimen using finite element simulation. It was determined that proper description of the minimum creep rate at 750°C required a threshold stress formalism. The magnitude of the threshold stress was determined to be 75MPa for creep tests using the conditions examined. This threshold stress arises from strengthening by the γ'(Ni 3 Al,Ti) intermetallic phase; above this temperature this phase is unstable and Alloy 617 behaves as a solid solution. Comparison of strengthening models to detailed TME analysis of dislocation-particle interaction in crept specimens indicated that strengthening arises from localized climb, or a combination of climb and Orowan bowing depending on the creep time and stress. Quantification of the strengthening from γ' is an important result to confirm the region over which it is acceptable to extrapolate creep rupture times on a Larson-Miller plot. This result will also help inform the activities underway in the US and Europe to develop a γ' strengthened version of Alloy 617 for application in ultra-supercritical fossil power plants.
doi:10.2172/1097703 fatcat:bzqcyyb5czfg3csptmnkvdl7m4