核电用690合金传热管抗苛性应力腐蚀性能评价

Evaluation of Caustic Stress Corrosion Resistance of Steam Generator Tubing Alloy 690 for Nuclear Power Plant

摘要:

采用C形试样浸泡的试验方法，评价了两种加载状态下三种690合金传热管在325℃的50%NaOH介质中长期抗苛性应力腐蚀开裂能力，用XRD方法测量加载后应力值，对表面氧化膜进行了细致的分析，结果表明：采用螺钉缓慢加载的C形试样最大载荷值存在一定量的释放，国产管比进口管的释放量大；在325℃的50%NaOH介质中，国产管与进口管均具有良好的抗SCC性能，国产A管与进口C管的表面氧化膜特征更接近；在高温浓碱介质中，690合金传热管良好的抗苛性应力腐蚀能力与表面生成的双层结构的氧化膜及沿晶界析出连续状碳化物结构特征相关。

Abstract:

With the long term immersion test of C-ring specimens loaded by two levels of load value, the caustic stress corrosion cracking resistance of three kinds of steam generator tubing alloy 690 in 50% NaOH at 325 ℃was evaluated. The stress value after loading was measured by XRD method and the oxide film after immersion was carefully analyzed. The results show that: (1) The maximum stress value of C-ring specimens is released to a certain extent after loading slowly by screw, and the release amount of load value of the domestic tubes is larger than that of the imported tubes; (2) The domestic tubes and the imported tubes all have good caustic-SCC resistance in 50% NaOH medium at 325℃, and the oxide film characteristic of the domestic tubing A are closer to that of the imported tubing C; (3) The good resistance of caustic stress corrosion of tubing alloy 690 in high concentrated alkaline medium at high temperature is related to the double-layer structured oxide film and the continuous carbide structure along grain boundary.