超(超)临界火电机组用关键钢管TP304L腐蚀现象分析

Corrosion analysis of TP304L pipe used for ultra-supercritical boiler

利用JSM-7001F扫描电子显微镜、Inca Energy350 X射线能谱仪等测试设备,对不合格的超(超)临界火电机组用TP304L钢管进行分析。结果表明,不合格的TP304L钢管内表面发生一定深度的腐蚀和沿晶腐蚀开裂。显微组织分析发现,管内表面晶界析出较多碳化物,而外表面很少,管心部组织也有少量碳化物。研究分析认为,出现沿晶腐蚀开裂和析出碳化物是由于在拉拔过程中发生高温快速渗碳的结果。

The unqualified TP304L pipes applied to ultra-supercritical thermal power units were analyzed by the JSM-7001F scanning electron microscope, Inca Energy350X energy spectrometer, etc. It is found a certain depth of corrosion occurred on the inside surface of the unqualified TP31）4L pipes in form of intergranular corrosion cracking. Microstructure analysis shows that there are more carbides precipitated at the grain boundaries on the inner surface of the pipes, and fewer on the outer surface or in the center of the pipes. It is considered that the intergranular corrosion cracking and carbide precipitation are due to high temperature and rapid carburizing during production.