Study on gear durability of austempered ductile cast iron with a large amount of retained austenite
2001
Ezoe, S. (Shimonoseki Univ. of Fisheries, Yamaguchi (Japan)) | Hashimoto, M. | Tanno, Y. | Asano, I.
It is well known that austempered ductile cast iron material (ADI) has a strength comparable to steel. However, stronger or tougher ADI material has been requested in order to increase the bending strength of gears. Recently, a special ADI material that included a large amount (55%) of retained austenite was developed. To evaluate the gear durability of the new ADI material, endurance gear tests were then carried out. The results obtained from the endurance tests were also compared with those of two conventional ADI gear materials that had retained austenite amounts of 36% and 10%. Consequently, it was clarified that the new ADI gear had a significant potential for increasing the surface durability as well as the bending strength of gears and the surface durability with an allowable stress over 1557 MPa. The Hertzian stress was comparable to that of case-hardened gear steel. According to the detailed analysis of the changes in local residual stress and in hardness at and under the tooth surface using an X-ray diffraction meter and micro-Vickers hardness meter, it seemed that the increase in the surface durability was due to compressive residual stress and work-hardenability induced by good running-in.
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