Fixing Induction Heat Treatment Flaws of an Automotive Transmission Output Shaft

Abstract

In the automotive manufacturing industries, heat treatment processes such as induction hardening or case hardening are required to meet the daunting demands of the customers in terms of quality and load-bearing capability of individual components. One of the key automobile engine components which almost always goes through some surface hardening is the transmission output shaft. Improper hardening of these components can create serious issues (i.e., catastrophic fracture) during actual service. Current article aims at understanding the mechanics of output shaft torque transfer, its vulnerabilities, the defects encountered during the induction hardening process and their relation to the premature failure of the transmission system output shaft. To this end, a comprehensive failure analysis has been performed on a defective induction-hardened part which showed significantly lower fatigue life including microstructural assessments, hardness testing, torque measurements and finite element analysis to shed light on the nature of failure and fracture of the component. Different possible contributing parameters were studied, and some remedial actions were provided to improve the process and to counter the reasons of the cracking in the process. The findings of this paper are in particular interests of failure analysis researchers, heat treatment experts, metallurgists and automotive engineers in industry and academia.