通过宏观检验、化学成分分析、力学性能试验、腐蚀试验、断口分析、能谱分析以及金相检验等手段对某项目6号机组3号高压加热器热交换器换热管发生泄漏的原因进行了分析。结果表明：该热交换器不锈钢管发生泄漏失效主要是因为介质中存在氯和氧元素(启停机凝结水)，在遮热板钻孔内壁和失效管外壁之间产生点蚀和缝隙腐蚀，破坏了换热管表面的钝化膜并形成点蚀坑(孔)，在热应力、冲击应力和振动应力作用下逐渐萌生微裂纹，最终发生应力腐蚀开裂和振动疲劳开裂，并导致泄漏。

By means of macro examination, chemical composition analysis, mechanical property test, corrosion test, fracture analysis, energy spectrum analysis and metallographic examination, the leakage reasons of stainless steel heat exchanger tubes of unit 3 high pressure heater No.6 group were investigated. The results show that the leakage of the stainless steel heat exchanger tubes was mainly caused by pitting corrosion and crevice corrosion of chloride ions and oxygen in the media (condensate water during running and stopping stages) between the inner drilling wall of shields and the outer wall of the failure tubes, which destroyed the tube surface passivation film and formed pits. The micro-cracks gradually propagated under the action of heat stress, shock stress and vibration stress, and finally stress corrosion cracking and vibration fatigue cracking happened, which resulted in the leakage of the tubes.