Digital Repository, ICF12, Ottawa 2009

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Evaluation of Type-IV Creep Damages in Thick Welded Joint for High Cr Steels
M. Tabuchi, H. Hongo, T. Watanabe, K. Sawada, Y. Takahashi

Last modified: 2013-05-06


Creep strength of welded joints in high Cr steels decreases due to the formation of
Type-IV creep damage in heat-affected zone (HAZ) during long-term use at high
temperatures. This paper aims to elucidate the processes and mechanisms of
Type-IV failure. Creep rupture and creep interruption tests for the welded joints
of Mod.9Cr-1Mo (ASME Gr.91) steel were conducted. Number and area fraction
of Type-IV creep voids were measured quantitatively. The measured distributions
of creep voids were compared with FEM computations using damage mechanics
analysis. It is considered that both the multiaxial stress state and strain
concentration in HAZ influence the evolution of creep voids.

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