压水堆主回路高温水中奥氏体不锈钢加工表面的腐蚀与应力腐蚀裂纹萌生:研究进展及展望

Corrosion and Stress Corrosion Crack Initiation in the Machined Surfaces of Austenitic Stainless Steels in Pressurized Water Reactor Primary Water:Research Progress and Perspective

奥氏体不锈钢是制造压水堆主回路部件的重要结构材料。奥氏体不锈钢在压水堆核电站中的服役整体表现优异,但服役过程中仍然发生过应力腐蚀开裂事故。发生冷变形是奥氏体不锈钢部件出现应力腐蚀开裂事故的主要原因,而切削加工及加工表面的后处理是在部件表面引入冷变形的主要工艺过程。本文基于过去20年本领域国内外相关研究结果,综述了切削加工等工艺在奥氏体不锈钢表面引入的塑性变形区的显微组织与残余应力特征,以及表面变形对奥氏体不锈钢在压水堆主回路高温水环境中的腐蚀及应力腐蚀裂纹萌生行为影响的研究进展。基于这些研究,指出了不锈钢应力腐蚀裂纹萌生研究中存在的问题、可能的解决办法,并对其他亟待开展的研究做了展望。

Austenitic stainless steels(ASSs)are important materials which are used widely in the primary circuits of pressurized water reactors(PWRs).The performance of the ASSs in PWR primary water has been outstanding.However,stress corrosion cracking cases have been identified in ASS components in the primary loop of PWR nuclear power plants since the end of 20th century.Most stress corrosion cracking cases occurred in low flow or stagnant zones in the dead-leg regions,where the primary water chemistry was contaminated with anionic impurities.Cold work has been identified to be necessary for stress corrosion cracking for components operating in locations where the water is well circulated.Machining and other surface treatments can always introduce cold work to ASS components.Therefore,considerable research efforts have been invested to understand the nature of the surface deformation layer on ASS introduced during machining processes and by other surface treatments,as well as the corrosion and stress corrosion crack initiation behaviors of the machined surfaces in simulated PWR primary water.This paper reviews the research progress on the surface deformation layer on ASSs introduced by various processes,and the effects of surface deformation on the corrosion and stress corrosion crack initiation behavior of ASSs.The key issues that remain to be solved are summarized,and possible solutions are suggested.