TY - JOUR A1 - Österle, Werner A1 - Urban, Ingrid A1 - Severin, D. A1 - Trepte, S. T1 - Correlations between surface modification and tribological performance of brake pads N2 - The formation of a third body layer on a conventional friction material during braking tests was studied in some detail using TEM, SEM, and X-ray photoelectron spectroscopy (XPS) techniques. Plate shaped micro-contact areas representing a compositional mix of all components of the tribocouple and exhibiting a nanocry stalline microstructure were identified after a run-in period. PY - 2001 U6 - https://doi.org/10.1179/026708401101517700 SN - 0267-0844 SN - 1743-2944 VL - 17 IS - 2 SP - 123 EP - 125 PB - Institute of Metals CY - London AN - OPUS4-2367 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Urban, Ingrid A1 - Severin, D. A1 - Trepte, S. T1 - Analyse von Reibschichten auf Bremsbelägen N2 - Die volle Leistung einer auf Reibung basierenden Bremse wird erst nach einem Einlaufvorgang erreicht. Dieser ist notwendig, um auf Belag und Scheibe eine sogenannte Reibschicht aufzubauen. Da diese Zwischenschicht das Reibungsverhalten des Systems maßgeblich bestimmt, ist es wichtig, sich Klarheit über ihre chemische Zusammensetzung, Mikrostruktur und die daraus resultierenden Eigenschaften zu verschaffen. Als Basismaterial diente ein phenolharzgebundener Belag Jurid 57-62, der mit verschiedenen Parametern (Flächenpressung und Umdrehungsgeschwindigkeit) gegen eine Stahlscheibe getestet wurde. Es wurden Dauerbremsungen von jeweils einer Stunde bzw. bis zu einem maximalen Belagverschleiß von 1 mm simuliert, wobei die Entwicklung der Reibzahl und die Oberflächentemperatur der Scheibe registriert wurde. Zur Analyse der Reibschichten auf dem Bremsbelag wurden mehrere Methoden parallel angewandt. So wurden Verschleißpartikel, die aus der Reibschicht stammen, gesammelt bzw. abgekratzt und nach Dispergieren auf Kohlefolien direkt im Transmissionselektronenmikros-kop (TEM) untersucht. Ferner wurden von einigen ausgesuchten Belagproben Mikrotom-schnitte sowie dünne Querschnittsfolien für die TEM-Untersuchung präpariert, um den Verbund Reibschicht-Grundmaterial darstellen zu können. Als Ergänzung wurden ferner oberflächenmorphologische und –analytische Verfahren wie REM/EDX und ESCA eingesetzt. Die Ergebnisse deuten darauf hin, dass die Reibschicht nanokristallin ist, und dass fast alle anorganischen Bestandteile des Bremsbelags sowie Eisenoxid von der Bremsscheibe in sehr fein verteilter Form vorliegen. Bei Belägen ohne Metallanteil bildet eine Barium-Eisen-Sulfatphase offenbar die Grundstruktur der Reibschicht, während auf eisenhaltigen Belägen Eisenoxid dominierend ist. Die nanokristalline Mikrostruktur entsteht, ähnlich wie beim mechanischen Legieren, durch einen Mahlvorgang von Verschleißpartikeln zwischen den Reibpartnern. Bei Überlastung des Belags tritt Zersetzung der Polymer-Bindephase ein, was zu einem raschen Anstieg der Verschleißrate führt. KW - Bremsbelag KW - Reibschicht KW - Reibungskoeffizient KW - Oberflächenanalyse KW - Transmissionselektronenmikroskopie PY - 2000 SN - 0933-5137 VL - 31 SP - 708 EP - 711 PB - Whiley VCH CY - Weinheim AN - OPUS4-38542 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Österle, Werner A1 - Urban, Ingrid A1 - Nebauer, E. A1 - Ressel, P. ED - Thomann, H. T1 - Metallurgie von Ohmschen Kontakten auf aktiven Halbleiterschichten T2 - Werkstoffwoche '96 (WW) CY - Stuttgart, Deutschland DA - 1996-05-28 PY - 1997 SN - 3-88355-229-1 VL - 1 SP - 199 EP - 204 PB - DGM Informationsges. CY - Frankfurt AN - OPUS4-2546 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Österle, Werner A1 - Urban, Ingrid A1 - Nebauer, E. T1 - Alloying reactions of Au-Ni-Ge ohmic contacts to n-GaAs PY - 1994 SP - 781 EP - 782 CY - Les Ulis AN - OPUS4-2479 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Österle, Werner A1 - Urban, Ingrid A1 - Kleinlein, H. A1 - Loemba, A. A1 - Trepte, S. T1 - Reibschichtbildung und mögliche Einflüsse auf Reibschwingungen bei einem Bahn-Bremsbelag T2 - Tagung CY - Hannover, Deutschland DA - 2002-11-26 PY - 2002 SN - 3-18-091736-9 SN - 0083-5560 N1 - Serientitel: VDI-Berichte – Series title: VDI-Berichte IS - 1736 SP - 283 EP - 296 PB - VDI-Verl. CY - Düsseldorf AN - OPUS4-2373 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Österle, Werner A1 - Urban, Ingrid A1 - Gesatzke, Wolfgang A1 - Rooch, Heidemarie ED - Bartz, Wilfried J. T1 - Characterization and evaluation of the formation of friction layers during braking with conventional PMC friction material against a cast iron rotor T2 - 14th International Colloquium Tribology, "Tribology and Lubrication Engineering" CY - Stuttgart, Germany DA - 2004-01-13 PY - 2004 SN - 3-924813-54-X VL - 1 SP - 483 EP - 489 PB - Techn. Akad. Esslingen CY - Ostfildern AN - OPUS4-3494 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Urban, Ingrid T1 - Third body formation on brake pads and rotors N2 - The surfaces of a brake pad and rotor were investigated after a run-in period during which a stable coefficient of friction had developed. The Focused Ion Beam Technique (FIB) was used to reveal tribologically induced surface films and for cross-sectional preparation of superficial layers. Additional information was obtained by TEM/EDS of thin lamellae prepared with the FIB and by surface analytical methods (GDOS, XPS and RS). Microscopic contact areas of the pad showed bright contrast in Scanning Ion Microscopy (SIM). This was attributed to severe plastic deformation finally leading to a nanocrystalline microstructure. Metallic particles of the pad, the so-called primary contact areas, were mostly covered with a smooth oxide layer of less than 1 µm thickness. Above this layer a thin (100 nm) partly amorphous film was often observed. The film was not only restricted to the metal particles, but also spread over adjacent regions, suggesting that secondary plateaus had formed. Similar layers and films, although with slightly different composition and structure, were also observed at the surface of the rotor. KW - Friction material KW - Friction layer KW - Friction film KW - Third body KW - Brake PY - 2005 U6 - https://doi.org/10.1016/j.triboint.2005.04.021 SN - 0301-679X VL - 39 IS - 5 SP - 401 EP - 408 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-12309 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Urban, Ingrid T1 - Friction layers and friction films on PMC brake pads N2 - A rather new tool, the focused ion beam (FIB) technique, was used to characterise superficial layers at micro-contact areas of a commercial brake pad. The friction material was a polymer matrix composite (PMC) with approximately 50% metal content (semi-metallic) and the counter part was a cast iron rotor. Though the contact areas were not visible as topographic features, they could be identified with the aid of their increased secondary electron emission during FIB-scanning of the surface after tribological activation. Target preparation of micron-sized cross-sections with the FIB enabled the study of superficial layers at predetermined sites at high magnification. Depending on the constituent of the pad, one, two or three layers were identified. The three layer structure comprised: (i) a 100 nm thick friction film containing nanocrystalline metal oxides and an amorphous phase which was enriched with sulphur, (ii) a nanocrystalline friction layer of compacted wear debris accommodating surface roughness and (iii) a severely deformed layer if the supporting constituent was a metal particle. Though the majority of loose wear particles was iron oxide, the friction film which adhered tightly to the pad surface contained a large amount of copper and sulphur, whereas zinc was transferred to the cast iron rotor. KW - Brake KW - Friction film KW - Friction layer KW - Oxidational wear KW - FIB PY - 2004 U6 - https://doi.org/10.1016/j.wear.2003.12.017 SN - 0043-1648 VL - 257 IS - 1-2 SP - 215 EP - 226 PB - Elsevier CY - Amsterdam AN - OPUS4-7645 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Kloß, Heinz A1 - Urban, Ingrid A1 - Dmitriev, A.I. T1 - Towards a better understanding of brake friction materials N2 - This work focuses on surface changes induced by repeated brake applications and tries to provide explanations, how such material modifications might affect friction and wear properties of automotive disc brakes. Surface films were investigated locally by transmission electron microscopy (TEM) after having prepared thin cross-sections with a focused ion beam instrument (FIB). Since the observed friction layers revealed a nanocrystalline structure, modelling with the method of movable cellular automata (MCA) was performed by assuming an array of linked nanometer-sized particles. In spite of complicated material combinations at the pad surface, two very characteristic features were always observed at both the pad and disc surface, namely a steel constituent—either ferritic (pad) or pearlitic (disc), partly covered with patches of nanocrystalline iron oxide, on a zone of severe plastic deformation with fragmented grain structure. When using an automata size of 10 nm, reasonable values for the mean coefficient of friction (COF) were obtained, namely 0.35 and 0.85 for oxide-on-oxide and metal-on-metal contacts, respectively. Immediately after brake application mass-mixing and bond-breaking was observed within a narrow zone at both surfaces. KW - Brake pad KW - Brake disc KW - Composite material KW - Friction layer KW - Third body KW - MCA-modelling PY - 2007 U6 - https://doi.org/10.1016/j.wear.2006.12.020 SN - 0043-1648 VL - 263 IS - 7-12 SP - 1189 EP - 1201 PB - Elsevier CY - Amsterdam AN - OPUS4-15735 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Griepentrog, Michael A1 - Gross, Thomas A1 - Urban, Ingrid T1 - Chemical and microstructural changes induced by friction and wear of brakes N2 - The chemical and microstructural changes occurring during braking simulation tests at the surface of a conventional brake pad material were investigated mainly by scanning and transmission electron microscopy and surface analytical techniques. It can be shown that patches of a third body material develop, comprising a compositional mix of all constituents of the pad and iron oxides from the disk. Milled debris particles still have the crystal structure of barite, the major phase of the pad material, but the grain size is reduced drastically to the nanometer scale. The major wear mechanism is delamination of filler particles from the organic binder, supported by local degradation of the phenolic resin during asperity heating. Quartz crystals are preserved thereby adopting the function of primary contact areas. KW - Brake KW - Third body material KW - Friction layer KW - Electron microscopy PY - 2001 U6 - https://doi.org/10.1016/S0043-1648(01)00785-2 SN - 0043-1648 VL - 251 SP - 1469 EP - 1476 PB - Elsevier CY - Amsterdam AN - OPUS4-2371 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -