The reason for the failure of titanium alloy seamless pipes!
In order to consider energy conservation and other factors, titanium alloy seamless pipes are used to cool the process media such as desalinated water and saturated steam of equipment related to the nuclear island system in coastal areas where both in-service and under construction nuclear power stations in China are built.
Titanium alloy seamless pipes have two morphologies: loose and hard lumps in the powder of unknown deposits, mainly composed of silicon, oxygen, iron, etc. This is a mixture of sediment and rust, and no titanium and titanium compounds have been detected, indicating that the unknown deposits are sediment and rust, and the titanium pipe has not been corroded. Further observation of the microstructure of the titanium tube fracture revealed a group of pits and fish scale like steps on the inner wall surface, with a smooth surface.
This is a typical trace caused by erosion and wear, which is the characteristic morphology analysis left by the erosion and wear effect of sediment containing seawater and its vortex erosion and wear effect. It is detected that the attachment on the surface of the inner wall of the fracture is sediment particles, further proving that the fracture is caused by sediment erosion and wear.
In summary, individual titanium pipes of titanium alloy seamless pipes were subjected to the combined action of sediment erosion and seawater whirlpool erosion, resulting in localized wear and tear of foreign objects on the inner wall, resulting in cracking. No titanium elements or their compounds were detected on the sediment left on the surface of the failed titanium alloy pipe fracture, so it can be ruled out that the titanium pipe is corroded by seawater. The surface of the inner wall of the failed titanium tube fracture contains smooth pits and irregular fish scale like patterns, which are typical local erosion and wear marks. Therefore, it can be considered that the fracture is caused by the combined action of sediment erosion and seawater vortex erosion and wear.
