采用光学显微镜、扫描电镜、能谱仪、X射线衍射仪和冲击试验机等, 研究了HR3C钢在600 ℃时效不同时间后的显微组织和室温冲击韧性。结果表明: 时效后HR3C钢的显微组织为奥氏体和析出相, 析出相主要为Nb(C,N)和M23C6; 随着时效时间的延长, 析出相数量不断增多, 其中M23C6沿晶界析出, 并不断聚集、长大成条块状, 最终相互连接; 时效初期, HR3C钢的冲击吸收能量明显下降, 断口形貌以韧窝为主, 时效200 h后冲击吸收能量的下降趋势减缓, 断口中沿晶裂纹数量增多, 时效500 h后的断口主要为沿晶断裂。

Microstructure and room temperature impact toughness of HR3C steel aged at 600 ℃ for different times were investigated by means of optical microscopy, scanning electron microscopy, energy dispersive spectrometer testing, X-ray diffractometer testing and impact testing. The results show that the microstructure of aged HR3C steel consisted of austenite and precipitated phases mainly including Nb(C,N) and M23C6. With the increase of aging time, the amounts of precipitated phases increased continuously, and M23C6 precipitated phase precipitated along grain boundaries, gathered and grew up into the bulk, finally connected to each other. At the beginning of aging, impact absorbed energy of the steel decreased obviously and the dimples was priority on fracture. After aging for 200 h, the decrease of impact absorbed energy became slow and the numbers of intergranular cracks on fracture increased. The intergranular fracture was main after aging for 500 h.