Technical Committee Lubricants

Investigation of the low speed wear behavior of case carburized gears lubricated with flow greases

In this research project, the influence of different grease parameters on the low speed wear behaviour of case carburised gears is systematically investigated and analysed. The focus lies on the influence of the base oil viscosity and type, the additive type, the type of soap thickener as well as the type and concentration of solid lubricants on the gear wear behaviour at low circumferential speeds. In order to systematically investigate the influence of each of these grease parameters on the wear behaviour, a suitable low speed wear test, based on the existing low speed wear test for gear oils according to DGMK 377-01, was developed. Under the boundary lubrication conditions prevalent in the developed test, the influence of the additive type on the wear behaviour is more significant than the influence of the base oil type and viscosity. Furthermore, the addition of the solid lubricants graphite and MoS2 to a grease leads to higher wear in comparison to the reference grease. Additionally, the influence of the lubricant on the scrape-mark that forms on the dedendum of the pinion as a result of the premature contact of the tooth tip of the wheel on account of the tooth deformation under load, is investigated. Lastly, the lubricant film thickness of selected base oils is measured using a twin disk machine. As a result of the systematic investigations conducted in the course of this research project, the existing knowledge base regarding the influence of different parameters of greases NLGI 00 on the wear behaviour of case carburised gears was expanded.

The IGF project 17067 N of the research association DGMK e.V. was funded by the Federal Ministry for Economic Affairs and Energy via the AiF within the framework of the programme for the promotion of joint industrial research and development (IGF) on the basis of a resolution of the German Bundestag.