Through visual inspection， macro/microscopic fracture morphology examination，microstructural characterization，and hardness testing of fractured bolts from a high-pressure oil filter subjected to 61 200 cycles of high-temperature pressure shock，this study investigated the abnormal fracture mechanism of GH4169 bolts connecting the outlet check valve and upper housing.The results indicate that the bolt fracture is fatigue-induced.Continuous chain-like Laves phases precipitated along grain boundaries significantly reduces material plasticity and abnormally increases notch sensitivity，ultimately triggering fatigue crack initiation.Additionally，stress concentration causes by small root radii at thread grooves and potential uneven assembly loads exacerbate fatigue crack propagation.This engineering failure case directly demonstrates the detrimental effects of grain boundary chain-like Laves phases on fatigue failure processes，providing critical insights to enhance researchers'' and engineers'' awareness of Laves phase-related hazards.