Creep deformation and rupture behavior of Alloy 617

Abstract

A series of creep data was obtained from creep tests at different applied stresses at the temperatures of 850°C, 900°C, and 950°C for Alloy 617, which is a leading candidate material for high-temperature components in Gen-IV nuclear reactor systems. The creep deformation and rupture behavior were investigated in terms of Norton's power law, Monkman–Grant relation (MGR), modified Monkman–Grant relation (MMGR), creep damage tolerance factor (λ), Zener–Hollomon Parameter (Z), and fracture behavior. Alloy 617 did not exhibit textbook creep behavior and revealed somewhat differences from typical heat resistant steels. The MMGR provided improved correlation between creep rate and rupture life in Alloy 617. The Z parameter obeyed a good agreement for a function of Z=2.30×1033 (σ/E)5.87, and the same creep mechanism was operative within the ranges tested in the present study. The value of λ for Alloy 617 was found to be 2.40, and this was in agreement with materials exhibiting typical cavitation damage. The creep failure analysis revealed a dominant intergranular fracture mode, which proceeds via initiation, linking, and incorporation of the cavities.