DLC-coated spur gears – part I: friction reduction
Industrial Lubrication and Tribology
ISSN: 0036-8792
Article publication date: 19 January 2021
Issue publication date: 14 May 2021
Abstract
Purpose
This paper aims to address the influence of diamond-like carbon (DLC) coatings on the frictional power loss of spur gears. It shows potentials for friction and bulk temperature reduction in industrial use. From a scientific point of view, the thermal insulation effect on fluid friction is addressed, which lowers viscosity in the gear contact due to increasing contact temperature.
Design/methodology/approach
Thermal insulation effect is analyzed in detail by means of the heat balance and micro thermal network of thermal elastohydrodynamic lubrication contacts. Preliminary results at a twin-disk test rig are summarized to categorize friction and bulk temperature reduction by DLC coatings. Based on experiments at a gear efficiency test rig, the frictional power losses and bulk temperatures of DLC-coated gears are investigated, whereby load, speed, oil temperature and coatings are varied.
Findings
Experimental investigations at the gear efficiency test rig showed friction and bulk temperature reduction for all operating conditions of DLC-coated gears compared to uncoated gears. This effect was most pronounced for high load and high speed. A reduction of the mean gear coefficient of friction on average 25% and maximum 55% was found. A maximum reduction of bulk temperature of 15% was observed.
Practical implications
DLC-coated gears show a high potential for reducing friction and improving load-carrying capacity. However, the industrial implementation is restrained by the limited durability of coatings on gear flanks. Therefore, a further and overall consideration of key durability factors such as substrate material, pretreatment, coating parameters and gear geometry is necessary.
Originality/value
Thermal insulation effect of DLC coatings was shown by theoretical analyses and experimental investigations at model test rigs. Although trial tests on gears were conducted in literature, this study proves the friction reduction by DLC-coated gears for the first time systematically in terms of various operating conditions and coatings.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0257/
Keywords
Acknowledgements
Erratum: It has come to the attention of the publisher that the article, Schwarz, A., Ebner, M., Lohner, T., Stahl, K., Bobzin, K., Brögelmann, T., Kalscheuer, C. and Thiex, M. (2021), “DLC-coated spur gears – part I: friction reduction” published in Industrial Lubrication and Tribology, omitted information from figure 7. This error was introduced in the production process and has now been corrected in the online version. The publisher sincerely apologises for this error and any inconvenience caused.
The presented results are based on the research project IGF 18490 undertaken by the Research Association for Drive Technology e.V. (FVA); supported through the German Federation of Industrial Research Associations e.V. (AiF) in the framework of the Industrial Collective Research Programme (IGF) by the Federal Ministry for Economic Affairs and Energy (BMWi) based on a decision taken by the German Bundestag. The authors would like to thank for the sponsorship and support received from the FVA, AiF and the members of the project committee.
Citation
Schwarz, A., Ebner, M., Lohner, T., Stahl, K., Bobzin, K., Brögelmann, T., Kalscheuer, C. and Thiex, M. (2021), "DLC-coated spur gears – part I: friction reduction", Industrial Lubrication and Tribology, Vol. 73 No. 3, pp. 457-469. https://doi.org/10.1108/ILT-07-2020-0257
Publisher
:Emerald Publishing Limited
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