高温时效对G115钢蠕变-疲劳裂纹扩展行为的影响

Effect of elevated-temperature aging on creep-fatigue crack growth behavior of G115 steel

在保载时间600 s,初始应力强度因子范围为23 MPa·m^(0.5)条件下,研究了G115钢在650℃时效1000、2000和3000 h后的蠕变-疲劳裂纹扩展行为。结果表明,随着时效时间的增加,时效后G115钢蠕变-疲劳裂纹扩展速率da/dN显著增加,导致裂纹扩展寿命降低。然而,时效时间的变化对裂纹扩展机制无显著影响,均为伴随大量蠕变损伤的穿晶主导混合断裂模式。沿边界Laves相的快速形核和长大、固溶作用的降低是导致时效后G115钢蠕变-疲劳裂纹扩展寿命降低的主要原因。

Creep-fatigue crack growth behavior of G115 steel aged at 650 ℃ for 1000,2000 and 3000 h was investigated under the condition of holding time 600 s and initial stress intensity factor 23 MPa·m~(0.5).The results reveal that the creep-fatigue crack growth rate da/dN increases with the aging time,causing the decrease of the crack propagation life.However,the change of aging time has no significant effect on crack propagation mechanism,which is a transgranular dominant mixed fracture mode with a large number of creep damage.The rapid nucleation and growth of Laves phase along the boundaries and the reduction of solid solution effect are the main reasons for the reduction of creep-fatigue crack growth life of G115 steel after aging.