Primary water stress corrosion cracking (PWSCC) in the weld metal of alloy600 is an issue of concern in a pressurized water reactor (PWR). As a countermeasure against PWSCC, water jet peening (WJP), which can change tensile residual stress into compressive residual stress, has been applied to welded joints. Microstructure in the target area of WJP has an influence of not only WJP but welding and machining. Especially machining introduces severe plastic deformations to the materials. So microstructure in the target area might lack thermal stability due to severe plastic deformation. Additionally the region that compressive residual stress by WJP is nearly up to 1mm from the surface of the target material. As PWRs are operated at about 596K for long term, the compressive residual stress by WJP may be relieved due to creep. In order to keep operating PWRs safety, the stability of the compressive residual stress by WJP at elevated temperature has been clarified. In this work, the results were obtained written below. As a result of thermal aging test, a relaxation of compressive residual stress at specimen surface layer occurred due to recovery of the plastic deformations by machining. This stress relaxation behavior followed Johnson-Mehl equation. However residual stress relaxation due to creep was very few. Therefore it has suggested that the compressive residual stress introduced in Alloy600 by WJP is confirmed to remain stable during long term operation under elevated temperature.

This content is only available via PDF.
You do not currently have access to this content.