Bearing flaking often initiates from the surface of the raceway under poor lubrication conditions. The life of a bearing with this type of surface originated flaking is usually much shorter than the calculated life. As global environmental issues continue to grow, the requirement to reduce the size and weight of machines to improve fuel consumption for given applications increases. Such a requirement makes the conditions for the rolling bearings used in these machines more severe, which increases the likelihood and accelerates surface originated flaking. Therefore, it is very important to develop bearings with increased resistance to surface originated flaking. The mechanism of surface originated flaking, however, is not fully understood. From previous studies of co-authors, it was obvious that fatigue crack initiation and propagation were strongly related to the direction of the tangential force acting on a raceway surface. It was also evident that the bearing life decreased as the tangential force increased due to an increase in the surface roughness of the rolling elements. These results indicated that bearing life can be extended by improving the resistance of the rolling elements to surface degradation. Based on the finding described above, a new material for rolling elements with a high surface hardness produced by nitride precipitates was developed. It was demonstrated that 6206 bearings with these rolling elements had a superior life when tested in lubricant contaminated with debris. Downsizing of a rolling element bearing can be achieved by using this newly developed material for rolling elements.
Author Information
Komata, Hiroki
NSK LTD., Basic Technology Research Center, Fujisawa-shi, JP
Iwanaga, Yasuhiro
NSK LTD., Basic Technology Research Center, Fujisawa-shi, JP
Ueda, Tohru
NSK LTD., Basic Technology Research Center, Fujisawa-shi, JP
Ueda, Koji
NSK LTD., Basic Technology Research Center, Fujisawa-shi, JP
Mitamura, Nobuaki
NSK LTD., Basic Technology Research Center, Fujisawa-shi, JP
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