Failure Analysis of Stainless Steel EH Tubing Used in Power Plant

The EH fuel pipe of stainless steel used in a power plant was cracked. The crack and leakage of stainless steel fuel pipe were detected and analyzed by alloy composition analysis, EDS, microhardness and metallographic structure. Results show that the alloy components conform to the requirements of the standard stainless steel EH fuel pipe's microstructure is normal, but EDS results show that Cl and S ions were detected in the crack aperture. The microhardness test found that the closer the hardness value is to the crack, the lower it is. Combined with the operating environment of EH tubing, the main reason for tubing cracking is that it absorbs moisture in the air and free Cl ions in a humid working environment, forming a corrosive medium. Under the action of working pressure and residual stress, stress corrosion cracking that expands from outside to inside occurs.