TiN夹杂物对690合金管在高温高压水中的腐蚀和应力腐蚀行为的影响

INFLUENCES OF TiN INCLUSION ON CORROSION AND STRESS CORROSION BEHAVIORS OF ALLOY 690 TUBE IN HIGH TEMPERATURE AND HIGH PRESSURE WATER

利用TEM和SEM观察了690合金管中TiN夹杂物的存在形式及其分布状态,通过高温高压电化学实验和应力腐蚀浸泡实验研究了690合金管在高温高压水溶液中的腐蚀和应力腐蚀行为.TiN是690合金管中一种主要的夹杂物,随机分布在奥氏体基体中.模拟压水堆核电站一回路水化学条件的高温高压电化学实验及能谱测试表明,点蚀优先发生在690合金管中含Ti夹杂物处.高温高压含Pb碱溶液中的应力腐蚀浸泡实验显示,690合金管表面的TiN和基体结合处的基体侧是优先发生腐蚀的位置,分布在晶界上的TiN和基体结合处发生腐蚀后容易导致局部应力集中,从而诱发沿晶应力腐蚀开裂.

TEM and SEM were used for studying the existing forms and distribution states of TiN inclusions in alloy 690. The corrosion and stress corrosion behaviors of alloy 690 were investigated through high temperature high pressure electrochemical measurement and immersion tests. TiN particles are the main inclusion in alloy 690 and randomly distribute in austenitic matrix. Corrosion experiments showed that pitting corrosion occurs preferentially at the inclusions containing Ti with high potential in simulated primary water of pressurized water reactor （PWR）. In high temperature high pressure alkali solution containing lead, the region near TiN inclusion and close to the side of matrix is the preferred position for corrosion, and TiN inclusions at grain boundary can subsequently cause local stress concentration on grain boundary, both of which lead to intergranular stress corrosion cracking in alloy 690.