TY - JOUR A1 - Theiler, Géraldine A1 - Gradt, Thomas T1 - Environmental effects on the sliding behaviour of PEEK composites JF - Wear N2 - The sliding performance of PEEK materials against steel discs was investigated in air, vacuum and hydrogen environment. KW - Sliding friction KW - PEEK KW - Graphite KW - TiO2 KW - CNTs KW - Vacuum KW - Hydrogen PY - 2016 DO - https://doi.org/10.1016/j.wear.2016.09.019 SN - 0043-1648 SN - 1873-2577 VL - 368 SP - 278 EP - 286 PB - Elsevier B.V. AN - OPUS4-37927 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wolter, Christian A1 - Österle, Werner A1 - Gradt, Thomas T1 - Metal sulphides as friction stabilisers under variable humidity T2 - Reibung, Schmierung und Verschleiß N2 - Neben Kohlenstoff werden Metallsulfide in jeder Standardrezeptur für Bremsbeläge als Reibungsstabilisatoren verwendet. Um deren Wirkung zu untersuchen, wurden verschiedene Pulvermischungen in einer Stift-Scheibe-Anordnung tribologisch beansprucht, um künstliche dritte Körper zu erzeugen und zu testen, deren definierte Zusammensetzungen aus drei wichtigen Bestandteilen einer realen Reibschicht bestehen: Magnetit, Graphit und div. Metallsulfide. N2 - Besides carbon, metal sulphides are used in every standard brake pad formulation as friction stabilisers. In order to investigate their impact, various powder mixtures were tribologically stressed in a pin-on-disc device in order to produce and test artificial third bodies. containing the three main components of a real friction film, namely magnetite, graphite and a metal sulphide of interest. Since the sliding behaviour is influenced by the relative humidity the powder mixtures are tested at low, medium and high moisture levels. The tests revealed that the presence of graphite dominates the friction behaviour as well as the humidity sensitivity. The powders were prepared by either manual mixing or high energy ball-milling. Interestingly, all ball-milled blends provided coefficients of friction within the desired range for braking, which was attributed to the effect of zirconia particles from wear debris of the milling balls. The zirconia particles prevent the formation of solid lubricant films on the surfaces and support a homogeneous mixture of all constituents of the powder. Optimum brake performance is gained by an optimum combination of solid lubricants and abrasives. T2 - 57. Tribologie-Fachtagung CY - Göttingen, Germany DA - 26.09.2016 KW - Friction KW - Metal sulphides KW - Brake pad formulation PY - 2016 SN - 978-3-9817451-1-5 SP - 1.5/1 EP - 1.5/6 AN - OPUS4-37838 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gradt, Thomas T1 - MoS2-Coatings for support elements in the Wendelstein 7-X nuclear fusion experiment N2 - The magnetic plasma confinement system of the nuclear fusion experiment “Wendelstein 7-X”, which recently produced the first plasma, consists of 20 planar and 50 non-planar superconducting coils. To keep them precisely in position, these coils contact each other at special support elements. The supports are operated in high vacuum at a temperature of about 4 K, and when the magnetic field is ramped up, forces up to 1500 kN and sliding motion of some mm occurs. Because mechanical disturbances may cause severe failures, only low friction without any stick-slip behaviour is tolerable. In pre-tests a PVD-MoS2-coating had proven to be the optimum solution. It was tested with downsized samples in reciprocating motion in liquid nitrogen (T = 77 K) and liquid helium (T = 4,2 K). In long-term tests in liquid nitrogen this coating showed stable sliding for up to 14.900 friction cycles without coating failure. However, in liquid helium an unexpected stick-slip effect occurred, whose origin could not be clarified so far. T2 - BAM Kolloquium Abteilung Werkstofftechnik CY - Berlin, Germany DA - 09.06.2016 KW - Kernfusion KW - Magnetischer Einschluss KW - Supraleitende Magnete KW - Tribologie KW - Festschmierstoffe KW - Magnetic confinement KW - Tribology KW - Lubricants KW - Superconducting magnet KW - Nuclear fusion PY - 2016 AN - OPUS4-38140 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gräning, Dirk A1 - Gradt, Thomas T1 - Sliding wear of martensitic steels in hydrogen – X30CrMoN15-1 and 100Cr6 – the role of water traces T2 - 57. Tribologie-Fachtagung (Tagungsbände) N2 - Die Untersuchung befasste sich ursprünglich mit dem Einfluss von gasförmigem Wasserstoff bei Normaldruck auf den Verschleiß von martensitischen Stählen. Dabei wurde als Gegenkörper eine Al2O3-Kugel verwendet, da dieser Werkstoff inert und zugleich hart ist und somit immer einen geringen Abtrag aufweisen sollte. Um 1 ppm Wasserstoff ohne thermomechanische Unterstützung in reines α-Eisen zu drücken, wird nämlich ein Druck von 15·105 MPa(~15 Mbar) benötigt. In der Versuchsreihe wiesen die Al2O3-Kugel in N2- und H2-Atmosphäre einen hohen Verschleiß auf, während bei Luft-Versuchen die Spur klein und der Verschleiß an der Scheibe groß war. Durch Streuungen und daraus folgenden Untersuchungen zeigte sich, dass Wasserstoff keinen merkbaren Einfluss hatte, Wasserspuren im Gas aber dafür umso deutlicher den Verschleiß beeinflussten. N2 - Initially the primary objective of the project has been the investigation of the influence of gaseous hydrogen on the wear of martensitic steels under heavy tribological stress. As a counter body an Al2O3 ball has been used because the material is inert and hard so that a low amount of wear was expected. If only the gas pressure is responsible for the absorption of hydrogen from the gas to pure α-iron it would require 15·105 MPa (~15 Mbar) to press 1 ppm into the material. In the test series the Al2O3 balls showed in N2 and H2 atmosphere a higher wear compared to aerial experiments which showed a smaller wear track and a severer wear for the disc. Because of scattering and thereof following investigations it was shown that hydrogen has no noticeable influence but water traces in the gas are manipulating the outcome of the tests distinctly. T2 - 57. Tribologie-Fachtagung CY - Göttingen, Germany DA - 26.09.2016 KW - Tribology KW - Hydrogen environment KW - Alumina KW - Martensitic steel KW - Adsorbed water film PY - 2016 SN - 978-3-9817451-1-5 VL - 2016 SP - 1.3/1 EP - 1.3/6 AN - OPUS4-40105 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gradt, Thomas A1 - Schneider, Thomas T1 - Tribological performance of MoS2 coatings in various environments JF - Lubricants N2 - Molybdenum disulfide (MoS₂) is a well-known solid lubricant for tribosystems running in vacuum or dry gases. Problems arise due to its sensitivity to humidity, which is a drawback for its application under ambient conditions. However, by using a physical vapor deposition (PVD) process, deposition parameters can be optimized not only to gain a coatings structure with favorable frictional properties but also to minimize the sensitivity to attack by water molecules. Therefore, an improved tribological behavior even under moist conditions can be achieved. MoS₂coatings are also candidates for being applied at cryogenic temperatures. They already have proven their suitability, e.g., for sliding support elements between superconducting magnets of the nuclear fusion-experiment Wendelstein 7-X. However, these coatings were exclusively produced for this particular application and the utilization for more common tribosystems may be precluded due to cost considerations. In view of a wider range of applications, pure and Cr containing PVD-MoS₂ coatings with an optimized structure were tested under varying environments including hydrogen gas and cryogenic temperatures. Results of the most promising variant are presented in this paper. KW - Solid lubrication KW - MoS2 KW - Extreme environments KW - Hydrogen KW - Cryogenic einvironment PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-381460 DO - https://doi.org/10.3390/lubricants4030032 SN - 2075-4442 VL - 32 IS - 4 PB - MPPI AG CY - Basel, Switzerland AN - OPUS4-38146 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -