Influence of tribological conditions on application relevant component properties of cold forged gears

In recent years there have been increasing attempts to enable the production of net-shape gears by forming methods. Cold forging enables improved material and energy efficiency compared to conventional gear manufacturing processes. In the extrusion process, a high surface quality, an increased hardness of the tooth profile as well as a load adapted fibre orientation is achieved. The procedure thus offers the potential to manufacture net-shape gears in a process suitable for series production. Due to the high tribological loads resulting from pronounced deformation and surface enlargement, the tribological conditions substantially influence the process result and the application relevant component properties. The tribological conditions are mainly affected by the applied lubrication system. The aim of this contribution is to investigate the influence of tribological conditions on the resulting component properties of cold forged steel gears. For this purpose different lubrication systems with and without a phosphate conversion layer are applied and the resulting component properties are determined. Phosphate-free lubrication systems offer substantial potential, especially from an ecological point of view. However, the high tribological loads during gear manufacturing pose a challenge. Based on the determined change of the tribological conditions and the resulting component properties, functional correlations are identified. The results show that friction has a distinct influence on the die filling and the application-relevant component properties.