在服役约7.8万h的600 MW超临界锅炉末级再热器不同位置截取T23、T91和TP347H钢管试样，分别进行显微组织和常温、高温拉伸性能分析，对比研究了显微组织和拉伸性能的劣化程度。结果表明：T23、TP347H和T91钢管试样的组织均呈现明显的老化特征，晶界处分别析出M₆C碳化物、M₂₃C₆碳化物和Laves相，显微组织老化级别分别为4级、3.5级和4级；T23钢管试样的常温和高温拉伸性能均呈现严重的劣化倾向，均不满足标准要求，T91钢管试样的抗拉强度明显下降，TP347H钢管试样的拉伸性能则满足标准要求；在高温状态下，TP347H钢管试样呈现良好的强度和结构安全性，但延展性明显降低。

T23, T91 and TP347H steel tube samples were taken at different positions of the final boiler reheater of a 600 MW supercritical boiler in service of about 7.8×10⁴ h. Microstructures and tensile properties at room temperature and elevated temperature of these samples were analyzed, and the deterioration degrees of the microstructure and tensile properties were studied and compared. The results show that the microstructures of T23, TP347H, T91 steel tube samples presented obvious degradation characteristics with M₆C carbide,M₂₃C₆ carbide and Laves phase precipitated on grain boundaries, and the microstructure degradation grades were grade 4, grade 3.5 and grade 4, respectively. The tensile properties of T23 steel tube samples at room temperature and elevated temperature showed serious deterioration tendency, and did not meet the standard requirements. The tensile strength of T91 steel tube samples decreased significantly. The tensile properties of TP347H steel tube samples met the standard requirements. Under elevated temperature conditions, TP347H steel tube samples had good strength and structural safety, but ductility was significantly reduced.