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Bending Fatigue Behavior of Carburized Gear Steels: Four-Point Bend Test Development and Evaluation
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Abstract
The ability to evaluate the bending fatigue behavior of carburized low alloy steels in a laboratory and relate these measurements to performance of high contact ratio helical gears is important to the design and development of transmissions. Typical methods of evaluating bending fatigue performance of carburized gear steels do not directly represent helical planetary gears because they lack the geometric and loading conditions of planetary pinions. The purpose of this study is twofold; 1) development of a lab fatigue test to represent the fatigue performance of planetary pinion gears tested in a dynamometer and 2) evaluation of the influence of alloy content on bending fatigue performance of two steel alloys. The steels under evaluation were modified 8620M and 4615M alloys machined into bend bars with a notch representing a gear root and carburized to a case depth of approximately 0.35 mm (using the same carburizing cycle as the planetary pinion gears). The samples were fatigued, under a fully reversed load condition (R=-1), in 4-point bending. Optical and electron microscopic evaluation of the case revealed the presence of internal oxides and NMTP (non-martensitic transformation products) at the surface of the modified 8620 alloy, the result of oxidation of Mn, Cr and Si. The modified 4615 alloy only showed Si and Mn oxidation without NMTP. 4615 modified alloy performance was more than 20% better in fatigue than 8620 modified. These differences in fatigue results are caused by the oxidation and resultant NMTP. These same materials were also evaluated as part of a dynamometer test program which resulted in similar relative fatigue behavior as found in lab experiments.
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Citation
Dowling, W., Donlon, W., Copple, W., Chernenkoff, R. et al., "Bending Fatigue Behavior of Carburized Gear Steels: Four-Point Bend Test Development and Evaluation," SAE Technical Paper 960977, 1996, https://doi.org/10.4271/960977.Also In
Transmission and Driveline Systems Symposium: Efficiency, Components, and Materials
Number: SP-1154; Published: 1996-02-01
Number: SP-1154; Published: 1996-02-01
References
- Cohen R.E. Haagensen P.J. Matlock D.K. Krauss G. SAE Paper 910140 1991
- Phelan P.E. Sell D.J. Dowling W.E. SAE Paper 960978 1996
- Chatterjee-Fischer, R. Met. Trans A 9A 1553 1560 1978
- Parrish, H.G. Heat Treatment of Metals 1 6 12 1976
- Namiki, K. Isokawa, K. Trans. ISIJ,26, 642 1986
- Namiki, K. Sugiura, S. Umegaki, S. Okada, Y. Tani, I. SAE Paper 890531 1989
- Koyasu, Y. Ochi, T. Takada, H. Isikawa, H. Kanisawa, H. Yanase, M. Naito, K. Nippon Steel Technical Report No. 53 April 1992
- Naito, T. Ueda, H. Kikuchi, M. Met. Trans A 15A 1431 1436 1984
- Inoue, K. Kato, M. Lyu, S. Onishi, M. Shimoda, K. “1994 Int Gear Conf.” 183 Fawcett J.N. Mech. Eng. Pub. Ltd London 1994