过热蒸汽管道的失效分析

Failure analysis of superheated steam pipe

通过微观组织分析、力学性能测试及微区成分能谱分析等方法,研究了过热蒸汽管道裂纹产生的原因,进行了热处理工艺重现试验,以及重现后的微观组织观察、晶粒尺寸统计、力学性能分析等研究。试验结果表明:管壁处裂纹的产生是发生了应力腐蚀,且裂纹被逐渐加宽形成分枝;Cr、Mo碳化物沿晶界析出并在晶界处连续分布,破环了晶界的结合;同时使得基体内Cr元素的贫化,晶界与基体腐蚀电位发生变化,加速应力腐蚀的发生。进行了热处理工艺重现试验后,其综合性能性能均优于原送检样。

Crack reasons for a superheated steam pipe were studied by microstructure analysis, mechanical property test and micro- component EDS analysis, the heat treatment process was reproduced, and microstructure and mechanical properties were studied after the reproduced experiment. The results show that the pipeline wall cracks occur because of stress corrosion and the cracks are gradually widened to form branches; Cr and Mo carbides precipitate along grain boundaries and continuously distribute along grain boundaries which destroy the bond of the boundaries ; At the same time, the depletion of Cr element in the matrix and the corrosion potential change between the grain boundary and the matrix accelerate the stress corrosion. Comprehensive properties of the samples after reproduced heat treatment are better than that of the original inspection samples.