Maßgeschneiderte Gleitlagerbeschichtungen für hochbelastete Lagerstellen durch Thermisches Spritzen

• Tailored coatings for highly stressed sliding bearings by thermal spraying

Wietheger, Wolfgang; Bobzin, Kirsten (Thesis advisor); Jacobs, Georg (Thesis advisor)

Düren : Shaker Verlag (2021)
Book, Dissertation / PhD Thesis

In: Schriftenreihe Oberflächentechnik 69
Page(s)/Article-Nr.: VI, 152, J Seiten : Illustrationen, Diagramme

Dissertation, RWTH Aachen University, 2021

Abstract

The main bearings of wind turbine generators (WTG) represent a particularly highly stressed bearing position. Currently, mainly rolling bearings are used in these turbines, but they are reaching their technical limits and thus have an impact on the electricity production costs of renewable energies. A promising alternative is the use of sliding bearings for this application, whose possible segmentation promises simple replacement in the event of damage, in contrast to the rolling bearings currently used. However, the use of conventional sliding bearings is usually limited to the field of hydrodynamics. For the prevailing load spectrum consisting of high dynamic loads and frequent start-up processes, high wear resistance must be ensured, in particular in the mixed friction area. One possibility for the production of customized sliding bearing coatings is the use of thermal spraying (TS). In this way, material combinations can be realized which cannot be produced by the processes used to date, such as roll cladding or centrifugal casting, or which are subject to restrictions in terms of shape and size. In this work, different feedstock materials were selected and applied by means of atmospheric plasma spraying (APS), a TS process variant. For the evaluation and selection of the coating systems, tribological high-load tests were carried out in a lubricated ring-disk tribometer. Overall, in the tribological investigations, a thermally sprayed cobalt-based coating ofCoCrAlYSi with hexagonal boron nitride in particular was able to provide the lowest material removal. This behavior was additionally confirmed by means of different sliding bearing test rigs and the coating system was selected for final evaluation for a demonstrator bearing. For the first time, a thermally sprayed sliding bearing coating was qualified as a substitute for conventionally used rolling bearings under realistic operating conditions for the main bearings of WTGs. The test was carried out using a system test rig at the Center for Wind Power Drives(CWD) at RWTH Aachen University. After more than n > 8,000 start-up cycles, corresponding to an operating time of about 8 years, no pronounced material removal was detectable. In this way, the potential of thermally sprayed sliding bearing coatings for the rotor main bearing of aWTG could be confirmed.