Effect Of Shot Peening On The Pitting Fatigue Strength Of Carburized Gears

Author:  Kobayashi, M. and Hasegawa, K.
Source:  Conf Proc: ICSP-4, (p.465-476)
Doc ID:  1990027
Year of Publication:  1990
Abstract:  
There are many reports to indicate that shot peening is a valid means to improve the bending strength of gear teeth, but there are only a limited number of reports on its effect on pitting fatigue strength and its mechanism is yet to be understood clearly. The authors investigated the conditions under which pitting of truck and bus transmission gears occurs and conducted a roller pitting fatigue test and a gear pitting fatigue test using spur gears in order to evaluate the effects of shot peening on the pitting fatigue strength of carburized gears. The findings obtained from the tests are listed below: (1) Pitting of carburized gears originates from the intergranular oxidation area on the surface produced by carburizing. (2) Shot-peened gears excel in both fatigue limit and fatigue life. (3) Electron microscopy of the sliding surfaces indicated that the residual compressive stress, which develops as a result of shot peening, works to suppress opening (cracking) of the intergranular oxidation layer under the Hertz's contact pressure and consequently improves the pitting fatigue strength. Descriptors: Shot peening; Carburized gear; Residual stress; Pitting fatigue