Effect of Cryogenic Treatment on Retained Austenite and Fatigue Life of Gcrl5 Wheel-Hub Bearing

摘要

Research and/or Engineering Questions/Objective There are many domestic enterprises that produce auto-hub bearings in China. But the majority of products are only applied in the after-sale market as the unstable quality of the domestic products can't meet the OEM's requirements. In order to improve fatigue life and dimensional stability of GCr15 steels, the cryogenic treatment was introduced to control the percentage of retained austenite of GCr15 bearing steel. Methodology The correlation between cryogenic treatment parameters and microstructure of the hub-bearing was studied. The percentage of retained austenite after different cryogenic treatments was measured by X-ray diffraction experimental. The equation was established to reveal the relationship between the percentage of retained austenite and cryogenic temperature. Finally, the fatigue life was performed by strengthen test according to JB/T 50013-2000 test rules of life and reliability of rolling bearings. Results After cryogenically treated in -40, -80, -120, -160, -196 °C chamber for 2 h, the investigation revealed that the retained austenite of the specimen surface is with proportional to the temperature decrease of deep cryogenic treatment. The specimens possess the maximum hardness and the minimum impact toughness during keeping at -80 °C deep cryogenic treatment temperature. Limitations of this study This study work has verified that the cryogenic treatment can improve the fatigue life and dimensional stability of wheel hub bearing. In order to obtain broader application and promotion, it requires further investigation on the characteristic properties of cryogenic treatment to be applied to other automotive bearings and other kinds of parts. What does the paper offer that is new in the field in comparison to other works of the author Since the mechanism of cryogenic treatment is not yet to be understood very well, So in general cryogenic treatment is still in the dormant level at present. In this study, we focus on investigating the mechanism and optimizing parameters of cryogenic treatment to improve the fatigue life of wheel-hub bearing. Conclusion The test results indicate the cryogenic treatment can improve the fatigue life of DAC 4007040 hub bearing, which runs 39.537 million revolutions, Re = 99.22 % by optimizing cryogenic treatment. In the same load conditions, the fatigue life of DAC 4007040 hub bearing subjected to conventional heat treatment is only 21.79 million revolutions in average, Re = 96.7 %.