采用慢应变速率试验(SSRT)方法, 研究了电极电位和应变速率对低合金钢-不锈钢异材焊接件16MND5/309L/308L在模拟压水堆一回路高温水环境中应力腐蚀破裂(SCC)的影响。结果表明: 在5×10-7 s-1应变速率条件下, 在-720~+100 mV(相对于标准氢电极SHE, 下同)的低电位区, 所有SSRT试样均在远离界面的308L焊缝金属区发生纯力学韧性断裂, 与在氮气中的试验结果类似; 当外加电位提高到+200 mV后, 试样在16MND5/309L界面发生SCC脆断, 界面附近的16MND5侧发生穿晶SCC, 309L侧发生沿晶SCC。该异材焊接件在该高温水环境中存在一个临界破裂电位, 高于此电位发生SCC, 在5×10-7s-1的应变速率下, 该临界破裂电位处于+100~+200 mV; 降低速应变率至1×10-7s-1, 临界破裂电位仍处于+100~+200 mV; 提高应变速率至1×10-6s-1后, 在+200~+300 mV电位区也没有显示出SCC。

Effects of electrode potential and strain rate on the stress corrosion cracking (SCC) behavior of dissimilar metal weld 16MND5/309L/308L in simulated primary water environment of pressurized water reactor (PWR) were investigated by means of slow strain rate testing (SSRT). Results showed that at strain rate of 5×10-7s-1, the SSRT specimens always failed in the bulk zone of stainless steel 308L weld metal with ductile appearance when tested in the potential range from -720 mV to +100 mV (vs. SHE). When electrode potential was raised to +200 mV, SCC happened in the 16MND5/309L interface area, with transgranular SCC in low alloy steel 16MND5 zone close to the interface, intergranular SCC in the 309L weld metal close to the interface. There was a critical cracking potential above which SCC occurred, within the range from +100 mV to +200 mV for the dissimilar metal weld when tested at the strain rate of 5×10-7s-1 in simulated primary water environment of PWR. When strain rate was decreased to 1×10-7s-1, the critical cracking potential was still within the range from +100 mV to +200 mV although the test time increased significantly. When strain rate was raised to 1×10-6s-1, SCC was not observed even at the potentials +200 mV and +300 mV.