【摘要】 采用显微组织分析和力学性能测试等方法研究了NF709R钢在700℃长时(10 000 h)时效后的显微组织和力学性能的变化。结果表明:在700℃时效过程中,钢中析出相主要有M23C6、MX和Z相;在4~3 400 h过程中,晶内细小的MX相、Z相和晶界处M23C6相的共同作用使钢的高温屈服强度逐渐升高;3 400~6 000 h过程中生成的M23C6碳化物疏松,晶界强度降低,使钢的高温屈服强度降低;6 000~10 000 h过程中,各种析出相变化不大,高温屈服强度缓慢下降;时效态室温塑性和韧性下降是由于M23C6相在晶界上长大、聚集成链状,使晶界变宽所致。更多还原

【Abstract】 Microstructure and mechanical properties changes of NF709R steel after long time aging at 700 ℃ were studied by microstructure analysis and mechanical properties test.The results show that the main precipitation phases in NF709R steel were M23C6,MX and Z at 700 ℃ aging.During 4-3 400 h,the high temperature yield strength of the steel raised gradually because of the fine MX phase in grains,Z phase and M23C6 in grain boundaries;and during 3 400-6 000 h aging,the high temperature yield strength decreased because of the loosening M23C6 which weaken grain boundaries strength;and during 6 000-10 000 h aging,the high temperature yield strength of the steel decreased slowly and all precipitation changed little.The M23C6 phases which grew up on the grain boundaries,gathered into chain and widened the grain boundaries resulted in the room ductility and toughness of NF709R steel as aging decreased.更多还原