New Material Concepts for Thermally Sprayed Hydrodynamic Bearings
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New Material Concepts for Thermally Sprayed Hydrodynamic Bearings ¨ te1 • T. Ko¨nigstein1 • W. Wietheger1 • T. Schro¨der2 K. Bobzin1 • M. O 2 • G. Jacobs D. Bosse2
•
Submitted: 22 June 2018 / in revised form: 21 September 2018 Ó ASM International 2019
Abstract Hydrodynamic bearings have to fulfill different requirements, depending on the operating conditions. Yet, conventional hydrodynamic bearings could not be used in critical operating conditions such as permanent start/stop operations. This is the reason why rolling bearings are currently used for frequent starting operations and low circumferential velocities, as they occur in wind turbines. In order to operate hydrodynamic bearings in a fail-safe manner even under these increased requirements, new bearing materials are needed. Within this study, two new bearing material concepts are developed and deposited by thermal spraying as coatings to interact in this tribological system. On the one hand, matrix materials containing friction-reducing solid lubricants and on the other hand, multilayer systems, which can be used in as-sprayed condition, are investigated. The aim of both concepts is to improve the operation properties under critical conditions. The coating concepts are therefore tested on a modified high-load ring-on-disk tribometer and are compared to a reference plain bearing material produced by conventional casting. In this way, it is shown whether these new
This article is an invited paper selected from presentations at the 2018 International Thermal Spray Conference, held May 7-10, 2018, in Orlando, Florida, USA, and has been expanded from the original presentation. & W. Wietheger [email protected] 1
Surface Engineering Institute (IOT), RWTH Aachen University, Aachen, Germany
2
Center for Wind Power Drives (CWD), RWTH Aachen University, Aachen, Germany
concepts can meet the requirements of slow-moving and highly loaded hydrodynamic bearings. Keywords bearing multilayer solid lubricant tribology wind energy
Introduction Usually, bearing materials are cast and subsequently rollbonded onto a steel substrate. These methods are limited to certain alloys. Complex material combinations are usually not producible. However, this restriction does not apply to thermal spraying (TS), as long as the material combinations can be produced as powders or wires (Ref 1, 2). Therefore, material concepts which cannot be manufactured by conventional melting processes can be produced as a coating by means of TS. Furthermore, the tribological properties in sliding contact can be positively affected by the surface topography of thermally sprayed coatings. TS is particularly suitable for producing functional surfaces which can be adjusted by process parameters. Various surface topographies can be realized and the process-dependent porosity can also add value to the tribological behavior compared with bulk materials. The surface topography, which is important for friction and wear resistance in sliding applications, is significantly affected
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