Increasing the load carrying capacity of highly loaded gears by nitriding

¹ Gear Research Centre (FZG), Technical University of Munich, 85748 Garching b. München, Germany
² Leibniz Institute for Materials Engineering – IWT, 28359 Bremen, Germany
³ Professor Hoffmann Werkstofftechnik, 28757 Bremen, Germany

^* Corresponding author. E-Mail: fzg@fzg.mw.tum.de

Abstract

Nitriding is a common heat treatment process for highly loaded gears. A very hard compound layer with a thickness of a few microns is produced at the surface of the gear. In the underlying material areas, a diffusion layer with nitride precipitations is formed. This publication summarizes the state of knowledge of nitrided gears and gives an overview of the current state of research in the field of nitrided gears. It can be concluded that a high load carrying capacity of nitrided gears is dependent on an adequate NHD and a stable compound layer. However, due to the increased surface roughness after nitriding, the risk of micropitting increases, too. Therefore, it may be favourable to grind the gears after nitriding. Ground gears also can provide a high load carrying capacity, but it must be taken into account that the wear performance will decrease significantly, since it is mainly influenced by the compound layer. In addition, nitrided gears usually show a high sensitivity against local load peaks. Beyond creating a stable compound the layer, the realization of a sufficient nitriding hardness depth with larger gear sizes is a focus in the current field of research.