GGB Study Delves into Micro-Tribological Processes

Structural and Chemical Alterations in Transfer Films

Dry running plain composite bearings have been of great interest for numerous applications because they feature remarkable sliding performance over a wide-ranging p,v-spectrum. The sliding performance of dry running shaft bearing contacts is affected by numerous factors. One essential factor is assuredly the formation and development of high quality transfer films on the shaft surface (attacking counter surface).

The present article explores the transfer film formation and accompanied processes in a common composite bearing shaft contact. Therefore wear and friction experiments were conducted using a Pin on Disk test device. The test conditions were: 11.3 MPa combined with a continuous sliding speed of 0.035 m/s. The experiments revealed fluctuating and re-measurable run-in friction and wear performance until the system enters its steady state stage. This fluctuation in performance was supposed to be caused by multiple processes taking place at the interface of both contacting surfaces throughout the sliding process.

Careful micro structural (SEM and FIB sections) and chemical analysis (EDX and XPS) were performed on the stressed surfaces to discover the nature of those processes. General surface observations of the attacking counter face and the worn pin surfaces discovered first insights regarding structural changes within the transfer film and bearing material. The micro structural analysis of the transfer films formed throughout the sliding process revealed structural alterations within the transfer film architecture with progress in covered sliding distance. Chemical analysis of the diverse transfer film stages provided useful information that chemical processes are also of crucial importance.

Taking all aspects into account the present paper confirmed the initial introduced hypotheses that observed friction and wear responses of the shaft bearing contact can be linked to structural changes within the transfer film and bearing material along with variations of the transfer film chemistry.

Dr. Marco Enger*                     marco.enger@ggbearings.com
Dipl.-Ing. Jürgen Eder               juergen.eder@ggbearings.com
Dipl.-Ing. Jürgen Erlewein         juergen.erlewein@ggbearings.com
Timo Ziegler, B.Sc.                    timo.ziegler@ggbearings.com

* corresponding author

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