Abstract: Through the macroscopic examination,metallographic examination, tensile test, the causes of the T23 tube burst of final superheater of a power plant are analyzed. The analysis results show that the burst of the tube is characterized by long overheating and material compliance with the standard requirements, but the metallurgical structure is seriously aging. The tensile strength of the tube section near the burst is obviously lower than that of the ASME standard. To sum up, the final superheater tube is running over temperature for a long time, resulting in its accelerated creep speed, dilated tube diameter and aging,resulting in creep holes, creep microcracks, and gradual expansion of micro cracks,leading to fracture of the whole tube.

Key words: final superheater tube, metallographic structure, tensile strength, creep microcrack