Creep-Fatigue Behavior of Uniaxial Cross-Weld and Stub Weld of HR6W

With an intention to clarify creep-fatigue behavior of welded joint of Ni-based alloy HR6W (23Cr-45Ni-6W), creep-fatigue tests at 700℃ were carried out for both uniaxial cross-weld and stub weld subjected to cyclic displacement. The location of crack at creep-fatigue life Nf was at a base metal near a Heat Affected Zone (HAZ) for uniaxial cross-weld; and at a toe of weld for stub-weld specimen. Elastic-plastic-creep FEM analysis using cyclic stress-strain behavior at Nf/2 was performed for the two types of welded joint to clarify a strain-concentration behavior and to predict a creep-fatigue life using a local strain. FEM results considering material behaviors depending on hardness distribution in welded joints, revealed that creep-fatigue life for the two types welded joint could be predicted by a factor of about two.