阴极保护下X65钢在模拟海水中的氢脆敏感性研究

采用阴极极化条件下的氢渗透实验和慢应变速率拉伸实验研究了X65钢在模拟海水中的氢渗透行为及其对断裂机理的影响。氢渗透实验结果表明,阴极极化过程中试样表面的钙镁沉积层能显著地降低氢扩散系数,采用Fourier方程、Laplace方程以及时间滞后法计算得出的有效氢扩散系数平均值为1.49×10-7cm2·s-1。结合变电位极化氢渗透测试结果、拉伸试样断口分析以及极化曲线测试,对阴极极化条件下X65钢的氢脆敏感性进行评估。结果显示,随着极化电位的降低,X65钢中的吸附氢浓度呈指数规律上升。当极化电位较高时,X65钢的裂纹扩展受阳极溶解和阴极析氢的双重作用控制。当极化电位较低,如-1200 mV时,钢中的吸附氢浓度急剧增加,脆性断裂区域的比例上升,X65钢发生氢致脆化失效。

Susceptibility to Hydrogen Embrittlement of X65 Steel Under Cathodic Protection in Artificial Sea Water

Hydrogen permeation behavior and its effect on cracking mechanism of X65 steel under cathodic polarization were studied in artificial seawater by means of electrochemical hydrogen permeation test and slow strain rate test (SSRT). Results show that the calcium magnesium deposits formed on the steel during cathodic polarization would significantly decrease the hydrogen diffusion coefficient; the effective hydrogen diffusion coefficient (D_eff) was calculated by Fourier method, modified Laplace method and time-lag method respectively, which give an average value 1.49×10^-7 cm²s^-1; the hydrogen concentration (C₀) in the sub-surface of the steel showed an exponential relationship with the polarized potential; the crack propagation was influenced by the synergistic effect of anodic dissolution and hydrogen evolution under the “soft” polarization conditions; however, if the polarized potentials were extremely negative, the concentration of hydrogen would increase sharply, as a result, the X65 steel became sensitive to hydrogen embrittlement.