Effect of rare earth on inclusions and fatigue properties of GCr15 bearing steel
WANG Li1, HAN Jie1, LIU Chengbao1, WANG Yi1, XU Rongchang1, YANG Chaoyun2
1. Research Institute of SD Steel, Shandong Iron and Steel Co., Ltd., Jinan 271104, Shandong, China; 2. Shenyang National Laboratory for Materials Sciences, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, Liaoning, China
Abstract：To investigate the effect of rare earth (La/Ce) on inclusions and fatigue properties of GCr15 bearing steel, the inclusions in bearing steels with different rare earth contents were analyzed and characterized by means of focused ion beam(FIB), energy dispersive X-ray spectroscopy(EDS), scanning electron microscope(SEM), non-destructive extraction and nano-indentation tests. The change of fatigue property for GCr15 bearing steel before and after adding rare earth (La/Ce) was analyzed by ultra high cycle fatigue test. The results show that rare earth elements react preferentially with O and S elements in steel to form rare earth oxysulfide inclusions, which can exist alone or coexist with other inclusions and distribute in steel as fine particles with their size less than 10 μm. Other hard inclusions, such as magnesia-alumina spinel, can also be coated by rare earth oxysulfide, which changes the irregular morphology of the inclusions. In addition, the equivalent elastic modulus and hardness between rare earth inclusion and matrix are closer, so their deformation difference is reduced under loading and the compatibility is enhanced. The anti-fatigue property of bearing steel is improved by modifying inclusion with rare earth addition. Under the condition of 50% failure probability for 107 cycles, the fatigue limit of GCr15-RE bearing steel with rare earth addition is 125 MPa higher than that of GCr15 bearing steel without rare earth addition, and the fatigue reliability is higher. These conclusions provide a theoretical basis for the modification of inclusions in bearing steel by rare earth and the performance optimization of GCr15 bearing steel.
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2023, Vol. 33 
