Against the leakage caused by local cracking drum of boiler water wall tubes in a thermal power plant

several test methods such as chemical composition analysis

metallurgical structure analysis

Vickers hardness analysis

scanning electron microscopy and energy spectrum analysis were carried out to find out the reasons. The results show that

under the acid conditions resulted from localized concentration of boiler water

the inner wall of the water wall tube is corroded

causing inner decarburization and micro crack on the inner wall. Such hydrogen damage results in cracking drum of the boiler tube. Moreover

Cl~– has a certain corrosion effect on the waterwall's inner wall

which causes thinning of the tube wall. In addition

local overheating of the water wall tube results in aging of the outer wall

namely spheroidization of the pearlite

but this does not have a serious influence on mechanical properties of the tubes.