Improvement In Tooth Surface Strength Of Carburized Transmission Gears By Fine Particle Bombarding Carburized Process

Author:  M. Yoshizaki, Hino Motors, Ltd.
Source:  Conf Proc: ICSP-10 Tokyo, Japan 2008
Doc ID:  2008068
Year of Publication:  2008
Abstract:  
Gear surface fatigue endurance tests were carried out using gears treated with the fine particle bombarding process (denoted hereafter as FPB) under three different peening conditions. Shot peened gears by a conventional impeller-type machine were used as comparison. The results showed that FPB increased the tooth surface strength (pitting resistance) by 1.21 to 1.28 times in Hertzian stress compared to the conventional impeller-type shot peening. Next, the influence of FPB on the tooth surface properties such as residual stress, hardness, roughness, surface texture, etc. were examined. After obtaining the results, the following factors of FPB that influenced tooth surface strength increase were discussed: (a) high residual compressive stress produced below the surface, (b) greatly increased hardness below the surface, (c) excellent conformability of the tooth surface, (d) micro hollows on the tooth surface generated after running. The author pointed out that the latter two were unique factors caused by FPB and contributed much to the improvement of tooth surface strength. Key Words Fine Particle Bombarding, Gear, Pitting, Spalling, Residual Stress.