硫和溶解氧含量对低合金钢高温高压水腐蚀疲劳性能的影响

Effect of Sulfur and Dissolved Oxygen Content on Corrosion Fatigue Property in High Temperature and High Pressure Water

试验研究了轻水堆核电站压力容器用低合金钢A533B在模拟核电高温高压水环境下的低周疲劳行为,具体为钢中硫含量和高温水中的溶解氧含量对钢疲劳寿命的影响和裂纹的萌生行为。结果表明,当硫含量小于0.015%(质量分数,下同),疲劳寿命随着硫含量的增加呈幂函数下降,当硫含量大于0.015%时,寿命趋于饱和;当硫含量较高时,疲劳裂纹为多裂纹源萌生,并且裂纹主要萌生于表面或者近表面含硫夹杂物;当溶解氧含量在0.05 mg/L至0.5 mg/L之间时,疲劳寿命随溶解氧的增加呈幂函数降低,当溶解氧含量大于0.5 mg/L和小于0.05 mg/L时,疲劳寿命趋于饱和;当溶解氧含量较高时,裂纹主要萌生于样品表面的点蚀坑;低溶解氧时,样品表面的腐蚀产物以Fe3O4为主,高溶解氧时腐蚀产物以Fe2O3为主。

Low cycle fatigue tests of reactor pressure vessel steel A533B were performed in simulated high temperature and high pressure water environment.Effects of sulfur and dissolved oxygen content on fatigue life and crack initiation were discussed.It was found that fatigue life decreased with increasing sulfur content in the steel when sulfur content was less than 0.015（wt） %,and fatigue life was saturated when sulfur content was more than 0.015（wt）%.Under high sulfur content condition,fatigue cracks were multiple initiation,and mainly nucleated at sulfur-bearing inclusions on or near the surface of specimens.Fatigue life decreased with increasing dissolved oxygen content in the water when dissolved oxygen content was between 0.05 mg/L and 0.5 mg/L.Furthermore,fatigue life was saturated when dissolved oxygen content was more than 0.5 mg/L or less than 0.05 mg/L.When dissolved oxygen content was high,cracks were mainly formed at pits on the surface.Fracture surface was mainly covered with Fe3O4 under low dissolved oxygen content condition,but with Fe2O3 under high dissolved oxygen content condition.