Effect of Thread Processing Sequence on Room Temperature Fatigue Performance of A286 Fasteners

The high frequency tensile fatigue test of heat-resistant fasteners of A286 alloy with different thread processing sequences was carried out by means of axial fatigue testing machine， metallographic microscope， microhardness tester and scanning electron microscope， and the metallographic of fatigue fracture and thread was analysed . The results show that machining thread after 720 ℃-12 h aging is beneficial to improve the stability of fatigue performance of fasteners， and has a slight effect on the median fatigue strength， but has no effect on the fatigue fracture mode. A large number of twins are formed on the surface of machined threads before aging， and the reinforced phase precipitates out at the twin boundary with large size particles during aging. Because the hardness of fasteners threaded before aging fluctuates greatly， it may also be the cause of the fluctuation of fatigue performance.