Nickel-based superalloys have been widely applied in the manufacturing of aero-engine hot-end components serving under extreme conditions. T
Nickel-based superalloys have been widely applied in the manufacturing of aero-engine hot-end components serving under extreme conditions. The development of advanced aero-engine technology puts forward demands for deeper understanding the underlying interactions between processing route, phase configuration and mechanical performance of nickel-based alloys, to seek novel theory and processing approach to maximize its serving capacity. In the present work, the creep characteristics of forged Inconel 718 alloy after different treatments were investigated, through which the relevant impact of grain configuration and intergranular δ phase on the creep mechanics and rupture mode was elucidated. Compared to the sub/super-solution plus aging cycles, the direct-aging treatment enabled the forged Inconel 718 the longest creep rupture life 894 h and the minimum steady-state creep rate 6.85·10−5 %/h at 650 °C/650 MPa with uniform grain configuration. When it evolved into duplexing grain configuration, the creep resistance was seriously degraded to result in the two orders of magnitude larger steady-state creep rate 1.52·10−3 %/h, meanwhile the secondary creep stage was shortened but the tertiary creep stage was prolonged, the creep rupture life was shortened to 494 h consequently. The existence of intergranular δ particles in uniform fine grain configuration was detrimental to creep performance, it shortened the secondary and tertiary creep stage simultaneously. Nevertheless, the intergranular δ particles were demonstrated to improve the creep ductility via transitioning the creep rupture mode from intergranular towards transgranular microvoid coalescence via facilitating the initiation and coalescence of ductile deep dimples.
