某热电厂高压锅炉在水压试验过程中水冷壁管发生开裂，通过宏观分析、壁厚测量、化学成分分析、硬度测试、金相检验、扫描电镜分析和能谱分析等方法，对水冷壁管的开裂原因进行了分析。结果表明：该水冷壁管是垢下腐蚀氢损伤导致的脆性开裂。水冷壁管发生氢腐蚀，且在腐蚀过程中汽水反应生成的部分原子氢扩散渗入金属内部，与珠光体中的碳化物反应生成甲烷，较大的甲烷分子聚集于晶界而使晶界开裂，在内壁形成沿晶微裂纹，裂纹扩展最终导致水冷壁管发生脆性开裂。

During the hydraulic test of a high pressure boiler in a thermal power plant, the water wall tube was cracked. The cracking causes of water wall tubes were analyzed by means of macroscopic analysis, wall thickness measurement, chemical composition analysis, hardness test, metallographic examination, scanning electron microscope analysis and energy spectrum analysis. The results show that the water wall tubes were brittle cracking caused by hydrogen damage under-deposit corrosion. Hydrogen corrosion occurred in the water wall tube, and in the process of corrosion, some of the hydrogen atoms generated by steam water reaction diffused into the metal, and reacted with the carbides in pearlite to form methane. The larger methane molecules gathered in the grain boundary and caused the grain boundary to crack. Microcracks were formed along the inner wall, and the cracks growth eventually led to brittle cracking of the water wall tube.