ABSTRACT

In many applications, the high demands regarding fatigue properties of transmission components can be reached only by the application of a customized case hardening. This case hardening process results in a wear resistant surface-layer in combination with a tough core.

However, as a side-effect the components get distorted during heat treatment. This distortion has a significant cost-impact because distorted components need to be hard-machined after heat treatment. Therefore, the proper control of distortion and the variation of distortion is an important measure to minimize production costs. 

By applying the technology of Low Pressure Carburizing (LPC) and High Pressure Gas Quenching (HPGQ) heat treat distortion can be significantly reduced. Especially for E-drive components significant cost-savings can be achieved compared to other process-combinations such as Atmospheric Carburizing with Oil Quenching.

HPGQ provides a very uniform heat transfer coefficient. The predictability of movement during quenching is more certain and uniform throughout the load. Further improvements can be achieved by optimizing the gas quenching parameters. Proper fixturing is another factor for distortion control. Modern CFC-materials (carbon reinforced carbon) are well suited as fixture-material for gas quenching. When compared to traditional alloy CFC demonstrates no deflection or distortion after many subsequent years of use. This paper provides insight into distortion values of transmission components for various applications after optimizing process parameters and the design of heat treatment fixtures.

Author(s): Volker Heuer, David Bolton, Jochen Friedel, Orlando Garcia

ISBN: 978-1-64353-152-6