Fatigue properties of B1914 superalloy at high temperatures

摘要

B1914 is a nickel-based superalloy with an increased amount of B (boron) and C (carbon) to reach an adequate amount of borides and carbides in the cast structure ensuring improved creep properties. However, the influence of the structure on the material high-cycle fatigue properties is not sufficiently described. The present study brings the experimental results on the high-cycle fatigue properties of a cast polycrystalline nickel-based boron-rich B1914 superalloy, obtained at temperatures of 800, 900 and 950°C. The cast superalloy was processed by hot isostatic pressing (HIP) to diminish the casting defects. The fatigue tests were performed in symmetrical loading in laboratory air. The fracture surfaces of the specimens were studied by scanning electron microscopy in order to describe the influence of temperature on the fatigue crack initiation and propagation. Change of the primary fatigue crack propagation mechanism from the crystallographic to the non-crystallographic mechanism was observed with increasing temperature. Decrease of a material lifetime and decrease of the fatigue endurance limit due to the increasing testing temperature was observed.