应力状态下核级奥氏体不锈钢表面加工对腐蚀的影响

Effect of Surface Processing of Nuclear Grade Austenitic Stainless Steel on Corrosion Under Stress

为了研究核级不锈钢在铣削加工中产生的残余应力对核级不锈钢应力腐蚀的影响,使用不同工艺参数对核级奥氏体不锈钢表面进行高速铣削加工,测量加工后的试样的表面残余应力。根据残余应力的方向和大小选取不同的试样。将选择的试样放入高温高压反应釜中模拟一回路水环境进行腐蚀试验,通过测量试样在腐蚀过程中的极化曲线,分析试样随时间变化的腐蚀情况。利用扫描电子显微镜观察腐蚀后的表面和截面的微观形貌,通过XRD分析腐蚀产物。研究结果表明:切削零件表面产生的应力是促进应力腐蚀的因素之一。残余拉应力加速应力腐蚀裂纹的生长,而残余压应力对应力腐蚀裂纹的生长具有一定阻碍作用。腐蚀过程中氯离子生成的氯化物是导致材料表面钝化膜破裂的主要原因。

In order to study the effect of the residual stress generated by the milling of nuclear grade stainless steel on the stress corrosion of nuclear grade stainless steel,different process parameters were used to perform high-speed milling on the surface of nuclear grade austenitic stainless steel,and the surface residual stress of the processed sample was measured.Different samples were choosed according to the direction and magnitude of the residual stress.The selected sample were put into the high temperature and high pressure reactor to simulate the water environment of the primary circuit for corrosion test.By measuring the polarization curve of the sample during the corrosion process,the corrosion situation of the sample over time was analyzed.Scanning electron microscope was used to observe the micro morphology of the corroded surface and cross section,and the corrosion products were analyzed by XRD.The research results show that the stress generated on the surface of cutting parts is one of the factors that promote stress corrosion.Residual tensile stress accelerates the growth of stress corrosion cracks,while residual compressive stress has a certain hindering effect on the growth of stress corrosion cracks.Chloride generated by chloride ions during the corrosion process is the main cause of the rupture of the passive film on the surface of the material.