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Frontiers of Mechanical Engineering >> 2019, Volume 14, Issue 3 doi: 10.1007/s11465-018-0489-7

Creep-fatigue crack growth behavior in GH4169 superalloy

. School of Energy and Power Engineering, Beihang University, Beijing 100191, China.. Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191, China.. Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191, China

Accepted: 2018-01-05 Available online:2018-01-05

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This study aims to examine the crack growth behavior of turbine disc GH4169 superalloy under creep-fatigue loading. Crack growth experiments were performed on compact tension specimens using trapezoidal waveform with dwell time at the maximum load at 650 °C. The crack growth rate of GH4169 superalloy significantly increased with dwell time. The grain boundaries oxidize during the dwell process, thereby inducing an intergranular creep-fatigue fracture mode. In addition, testing data under the same dwell time showed scattering at the crack growth rate. Consequently, a modified model based on the Saxena equation was proposed by introducing a distribution factor for the crack growth rate. Microstructural observation confirmed that the small grain size and high volume fraction of the d phase led to a fast creep-fatigue crack growth rate at 650 °C, thus indicating that two factors, namely, fine grain and presence of the d phase at the grain boundary, increased the amount of weakened interface at high temperature, in which intergranular cracks may form and propagate.

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