对比研究了供货态和高温服役5万h后HR3C钢的显微组织和力学性能，分析了服役过程中影响力学性能的主要因素。结果表明：与供货态组织相比，服役后HR3C钢的显微组织仍由奥氏体基体+析出相组成，但析出相数量增多、尺寸增大，奥氏体晶界和晶内均主要析出了M₂₃C₆碳化物；服役后HR3C钢的抗拉强度变化不大，塑性下降，在弯曲过程中该钢在产生少量塑性变形后发生脆断；服役后HR3C钢的冲击功降低，冲击断口呈现典型的沿晶断裂特征；M₂₃C₆碳化物的沿晶析出与长大是HR3C钢塑性和韧性下降的根本原因。

Microstructures and mechanical properties of HR3C steel in as-received state and after 50 000 h service at high temperature were studied and compared. Main factors influencing the mechanical properties during service were analyzed. The results show that compared with the microstructure in as-received state, the microstructure of HR3C steel after service still consisted of austenite matrix and precipitates, but the amount and size of the precipitates increased. The precipitates on grain boundary and inside grain of austenite were mainly M₂₃C₆ carbide. After service, the tensile strength of HR3C steel changed little while the plasticity decreased; during bending, the steel had only a small amount of plastic deformation before brittle fracture. After service, the impact energy of HR3C steel was reduced and the impact fracture showed a typical intergranular fracture feature. The intergranular precipitation and growth of M₂₃C₆ carbide was the root cause of the decline of plasticity and toughness of HR3C steel.