采用慢应变速率试验(SSRT),对304L不锈钢在180~220℃、1.5%~6%(质量分数)NaOH溶液中的应力腐蚀开裂行为进行了研究,结合扫描电镜和光学显微镜分别对断口形貌进行了表征并计算了二次裂纹的深度及扩展速率。结果表明:二次裂纹扩展速率更能体现“碱脆体系”中金属的应力腐蚀敏感性,304L在上述高温NaOH溶液中的应力腐蚀开裂敏感指数差别不大。SSRT后的断口微观形貌显示试样为韧性断裂,但由宏观形貌发现了二次裂纹,二次裂纹深度和扩展速率随温度的升高、NaOH浓度的增加均增大。304L在180℃、1.5% NaOH溶液中可能有一定的应力腐蚀开裂倾向。

The stress cracking corrosion behavior of 304L stainless steel in 180-220 ℃, 1.5%-6% (mass fraction) NaOH solution was studied by slow strain rate test (SSRT). The fracture morphology was characterized by scanning electron microscopy and optical microscopy, and the depth and propagation rate of secondary cracks were calculated. The results showed that the secondary crack growth rate could respectively good reflect the stress corrosion cracking sensitivity of metals in “alkali brittle system”, and the stress corrosion cracking sensitivity index of 304L in above high temperature NaOH solutions had little difference. The micro morphology of the fracture surface after SSRT showed that the sample was ductile fracture, but the macro morphology found secondary cracks. The depth and growth rate of secondary cracks increased with the increase of temperature and NaOH content. 304L might have a certain stress corrosion cracking tendency in 180 ℃, 1.5% NaOH solution.