Reliability Design for Bending Fatigue Strength of Carburized Gears of Low-Carbon Case Hardenable Steels 20CrMo, 20MnCr5, and SAE 8620

Bending fatigue test was performed on carburized gears made of different low-carbon hardenable steels such as 20CrMo, 20MnCr5, and SAE 8620. Hardness assessment and microstructure examination were conducted to confirm the homogeneity of phase presence and absence of network carbides and decarburization. Stress levels were chosen to find the fatigue limit of the different carburized gear materials. Fatigue life of the component can be predicted at various stress level with available test data by using Weibull distribution, which is suitable for random failure data. By fitting this failure data at various stress level, actual fatigue strength of the component can be calculated at different reliability. Reliable fatigue design for three different materials are predicted and compared, which disclosed SAE 8629 as superior.