核电站凝汽器用钛焊管蒸汽腐蚀疲劳性能研究

Research on Water Vapor Corrosion Fatigue Properties of Titanium Welding Tube Used for Nuclear Power Station Condenser

测定了国产和进口核电站凝汽器用钛焊管在室温大气和人工海水100℃水蒸汽介质中的疲劳性能,同时采用扫描电子显微镜对疲劳断口进行了观察,探讨了钛焊管的蒸汽腐蚀疲劳机理。研究结果表明:国产钛焊管与进口钛焊管的疲劳寿命较为接近,水蒸汽氛围大幅度降低了钛焊管的疲劳寿命;疲劳试样的裂纹均萌生于钛焊管焊缝区域的外表面,多为多源萌生,裂纹扩展均以条纹机理为主;断口处有少量二次裂纹,未发现沿晶断裂及周期解理断裂特征,静断区断口形貌为韧窝;从蒸汽腐蚀疲劳试样中,未能观察到明显的腐蚀产物;钛焊管的蒸汽疲劳腐蚀是交变应力和电化学腐蚀交互作用的结果。

Corrosion fatigue properties of domestic and imported titanium welding pipes were evaluated in atmosphere at room temperature and artificial seawater vapor at 100℃. The fatigue fractures were observed by scanning electron microscope. The mechanism of water vapor corrosion fatigue was investigated. The results show that the domestic and imported welding tubes show similar fatigue live.The fatigue life is intensively reduced by water vapor. Fatigue crack initiates from the external surface of weld zone, and widely exist as multiple origins. The growth of crack is based on the striation mechanism. A few secondary cracks are found in the fractures surface. However, neither intergranular fracture nor periodic cleavage is found. Dimple is the morphology of static fracture. No obvious corrosion products were observed in water vapor corrosion fatigue specimens. Water vapor corrosion fatigue of titanium welding pipe is the result of interaction between alternating stress and electrochemical corrosion.