在模拟核电厂一回路高温高压水环境中,对国产化锻造主管道用316LN不锈钢开展了疲劳试验,分析了应变速率和溶解氧(DO)含量对不锈钢环境促进疲劳(EAF)寿命的影响。结果表明:在不同DO含量下,试样EAF断口均呈典型的多裂纹源疲劳开裂特征,疲劳辉纹明显;断口上覆盖的腐蚀产物主要为富Fe、Cr、Ni的尖晶石氧化物,随着DO含量的增加,氧化物颗粒数量增加、尺寸变大;在不同DO含量下EAF寿命偏差不超过30%,无明显统计差别;结合不同的统计模型可知,在低应变速率(0.1×10^-4~0.1×10^-3 s^-1)下DO含量对316LN不锈钢EAF寿命的影响才会比较明显;在建立较为精确的统计模型时,需要细分应变速率范围,并考虑DO含量的影响。

The fatigue tests of 316LN stainless steel used for domestic forged main pipes was carried out in simulated high temperature and high pressure water environment of nuclear power plant primary circuit. The effects of strain rate and dissolved oxygen (DO) content on the environmental assisted fatigue (EAF) life of stainless steel were analyzed. The results showed that under different DO contents, the EAF fracture of the samples showed typical multi-crack source fatigue cracking characteristics, and the fatigue striation was obvious. The corrosion products covered on the fracture were mainly spinel oxides riched in Fe, Cr and Ni. With the increase of DO content, the number and size of oxide particles increased. The deviation of EAF life under different DO contents was less than 30%, and there was no significant statistical difference. Combined with different statistical models, it could be seen that the effect of DO content on EAF life of 316LN stainless steel was obvious only at low strain rate (0.1×10^-4-0.1×10^-3 s^-1). When establishing a more accurate statistical model, it was necessary to subdivide the strain rate range and consider the influence of DO content.