Evaluation of Surface Integrity Aspects Induced by Different Gear Manufacturing Paths for Electric Vehicle Transmission Systems

The mobility electrification process is currently of great interest due to its environmental appeal, but it is accompanied by new technical requirements for vehicle systems, the powertrain being one of those with the most significant trade-offs to be solved. Higher power densities, higher torque efficiency and lower noise and vibration generation are simultaneously required. The literature shows that the manufacturing chain can influence the final state of surface integrity of a part, which affects the operational behavior and service life of a component. Therefore, a customized transmission system design for electric propulsion requires several analyses, from the raw material to the gear manufacturing processes, so that surface integrity plays a significative role in the required performance. From the perspective of their capability to meet the e-mobility requirements in terms of surface integrity is essential to conduct a comparative analysis of gear manufacturing processes. So, the objective of this study is to evaluate the influence of surface integrity induced by gear grinding and shaving processes on the contact fatigue. Gear samples were manufactured by the grinding and shaving finishing processes and compared in terms of the obtained topography, manufacturing deviations, carburized layer and induced residual stresses. Contact fatigue tests performed in a circulating power test rig evidenced that the intergranular oxidation present in the shaved gears is critical in terms of micropitting related-failure in gear teeth when compared to the ground gears. However, lower roughness values obtained in the shaved gears are promising aspects compared to the ground gears.