The Effect Of Shot Peening On Contact Fatigue Life Of Carburized Steel

Author:  Cheng, J. and Ao, B.
Source:  Conf Proc: ICSP-1, (p.333-340)
Doc ID:  1981070
Year of Publication:  1981
Abstract:  
With carburized and hardened 20CrMnTi steel ring specimens, contact fatigue experiments were performed under sliding-rolling conditions. The contact fatigue lives of shot-peened specimens was compared with those of non-shot-peened specimens. The hardness distributions, residual stress distributions and their changes during the process of contact fatigue were measured. The microstructure and failure characteristics were inspected and analysed. The relations between the factors mentioned above were discussed. It is established that there are three kinds of cracks: surface cracks, shallow subsurface cracks and deep subsurface cracks. With different conditions of growth and joining-up, these cracks would develop into pittings, shallow spallings or deep spallings. Under high contact stresses together with shot-peening, a shallow subsurface crack usually occurs and develops into shallow spallings just below the strengthened layer. A certain relaxation of residual compressive stress will occur rapidly near the shot-peened surface layer. Under ordinary service loadings of gears (the contact stress lower than 225kg/mm2), shallow spallings would hardly occur; the initiation and propagation of surface cracks were depressed by shot-peening and the contact fatigue lives of the shot-peened specimens, therefore, would be improved. Descriptors: Surface crack; Shallow subsurface crack; Deep subsurface crack; Pitting; Shallow spalling; Deep spalling