Effect of cyclic loadings on the stress corrosion crack growth ratein Alloy 600 in PWR primary water

摘要

Fatigue air pre-cracked Compact Tensile (CT) specimens in Alloy 600 were tested in primarywater (325 ℃) of Pressurized Water Reactors (PWR). In order to assess the effect of cyclicloading on crack growth, CT specimens are tested under constant loadings and lowfrequencies cyclic loadings: triangular and saw-tooth. Two Alloy 600 materials, with differentintrinsic susceptibility to Stress Corrosion Cracking (SCC), are studied. Crack growth ratesare monitored in-situ by the direct current potential drop method and are validated by postmortemobservations. Fracture surfaces are characterized by macroscopic and microscopicobservations. Comparison of the crack growth rate and of the fracture features demonstratedthat they depend on the characteristics of the mechanical loading (constant, triangular or sawtooth)and on the material intrinsic sensibility to SCC.