Study On Accelerating Spheroidization And Contact Fatigue Property Of Bainitic Bearing Steels Containing Aluminum

A new acceleration spheroidization progressing has been developed for thehigh-carbon high-chromium bearing steels containing aluminum in this research. Underthe process we can save the time and cost in spheroidization. Besides, we also explore themechanism of aluminum during the spheroidizing process and the fatigue property ofbainitic bearing steels.Under the spheroidization experiment of a novel kind of carbide-free bainitic bearingsteel-GCr15SiAlMo, a new cyclic spheroidization annealing process, suitable for bearingsteel, is optimized. The microstructures of the steels spheroidized are observed by thescanning electron microscopy (SEM) and the X-ray diffraction (XRD). The results showthat the GCr15SiAlMo bearing steels with the microstructures of carbide free bainite hassatisfactory properties under the carbide spheroidization. After4cycles, the microstructuremostly contains spheroidized carbides, but there are a lot of lamellar carbides in themicrostructures spheroidized at700℃for10h. Consequently, compared with theconventional spheroidization process, the cyclic spheroidization process is more rapid andfully. Under the spheroidization annealing, the average diameter of the carbides is lessthan0.55μm. The diameter of the carbides less than1μm is more than93%, and someeven reach99%. Meanwhile, these results show that Al can enhance the A1point of thebearing steels and suppress the precipitation of the network carbides. Besides, addingmoderate aluminum will improve the annealing process and restrain the carbide growth inthe steels. Moreover, during the process of slow cooling transformation of hypereutectoidsteel, the interlamellar spacing of pearlite has been reduced by adding aluminum.Compared with the conventional spheroidization process, deformation can obviouslyaccelerate the process of spheroidization of lamellar cementite in the steels and cutspheroidization time. With deformation temperature reducing, the deformation storedenergy increases, which will promote the diffusion of carbon in the steels. However,aluminum is not always helpful for spheroidization of lamellar cementite. When thecontent of Al in the steels exceeds the critical value, spheroidal carbide will coarsen.