Z. Li, B. L. Ferguson, Deformation Control Technology, Inc., Cleveland, OH; S. Zhang, GM Powertrain, Ypsilanti, MI

Summary: By increasing the carbon content of a specific steel, the diffusive transformations are retarded, the martensitic transformation starting temperature is decreased, and the strength of the steel is increased. As a combined effect, the carburization process generates compressive residual stress in the surface of the component during quenching. The carbon distribution in the carburized case has a significant effect on the residual stress distribution after quenching. In this paper, the carbon distributions produced by different carburization schedules are modeled. The effect of these different carbon distributions on the residual stress distribution of a transmission shaft is predicted using DANTE, a commercial heat treatment simulation software. The hardness, volume fraction of phases, and shaft distortion are predicted. Experimental measurement of the carbon profiles and the residual stress distributions are used to validate the simulation results. Once validated, the modeling capability will be used to optimize the residual stress profile and the corresponding fatigue life by control of the carburization schedule.