This paper describes a program aimed at betterunderstanding the effect of surface condition on PrimaryWater Stress Corrosion Cracking (PWSCC) initiation ofAlloy 600. Manufacturing techniques used on plantcomponents can induce residual stresses, changes to themicrostructure and plastic deformation at the surface ofcomponents, whilst affecting the surface roughness. Thisstudy examines surface condition factors and their effecton PWSCC initiation susceptibility to inform mitigationapproaches. Advances to the understanding of the SCCinitiation test method, via finite element modelling andunderstanding of in-test strains, will also be presented insupport of this aim.Surface roughness, residual stress and the depth ofdamage and nano-crystalline surface layers induced bymachining were characterized using profilometry, X-RayDiffraction (XRD), micro-hardness and ElectronBackscatter Diffraction (EBSD). Initiation tests usedtensile specimens manufactured from Alloy 600 withvarying cold work levels, orientation with respect to coldwork, surface roughness, depth of nano-crystalline surfacelayers, and surface residual stress (ranging from highlytensile to highly compressive). Tests were conducted at360°C, with active loading to yield in a PWR primaryenvironment. The onset of initiation was detected by in-situDirect Current Potential Drop (DCPD) measurement.Results indicate that residual stress and orientation withrespect to cold work are critical parameters for Alloy 600PWSCC susceptibility, with PWSCC mitigated bycompressive residual stresses.
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