TY - JOUR A1 - Berger, L.-M. A1 - Saaro, S. A1 - Stahr, C. A1 - Thiele, S. A1 - Woydt, Mathias T1 - Entwicklung keramischer Schichten im System Cr2O3-TiO2 / Development of ceramic coatings in the Cr2O3-TiO2 system JF - Thermal spray bulletin N2 - In der vorliegenden Arbeit wurden die Herstellung und die Eigenschaften von APSund HVOF-gespritzten Schichten aus dem gesamten System Cr2O3-TiO2 erstmalig systematisch untersucht. Für die Herstellung experimenteller Beschichtungspulver auf der TiO2-reichen Seite, aber auch für die Interpretation der Phasenzusammensetzungen der Schichten wurde das Cr2O3-TiO2-Phasendiagramm eingehend analysiert. Neben kommerziell verfügbaren Pulvern auf der Cr2O3-reichen Seite wurden im Rahmen der Arbeit fünf durch agglomerieren und sintern hergestellte experimentelle Pulver auf der TiO2-reichen Seite verwendet. In diesen experimentellen Pulvern konnten die angestrebten Phasenzusammensetzungen gezielt eingestellt werden. Mit beiden Spritzverfahren konnten homogene und porenarme Schichten hergestellt werden. Durch die Spritzprozesse kommt es zu erheblichen Veränderungen der Phasenzusammensetzungen. Bei der Schichthärte, dem spezifischen Widerstand der Schichten, als auch bei der Beständigkeit im ungeschmierten Reib-/Gleitverschleiß existiert eine Abhängigkeit der Eigenschaften vom Cr2O3-Gehalt. Die erwarteten niedrigen spezifischen Widerstände auf der TiO2-reichen Seite wurden bestätigt. Als hochtemperaturstabile, elektrisch leitfähige keramische Schichten besitzen sie ein hohes Anwendungspotential. Die Vorteile der Schichten im ungeschmierten Reib-/Gleitverschleiß liegen bei Hochtemperaturanwendungen. KW - Thermal spraying KW - Dry sliding KW - High temperature KW - Cr2O3 KW - TiO2 KW - APS KW - HVOF KW - Cermet KW - (Ti,Mo)(C,N) KW - Dry PY - 2009 SN - 1866-6248 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 2 IS - 1 SP - 64 EP - 77 PB - DVS-Verl. CY - Düsseldorf AN - OPUS4-19392 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Berger, L.-M. A1 - Saaro, S. A1 - Woydt, Mathias T1 - WC-(W,Cr)2C-Ni - die "unbekannte" Hartmetallschicht / WC-(W,Cr)2C-Ni - the 'Unknown' Hardmetal Coating JF - Thermal spray bulletin N2 - Die Zusammensetzung WC-(W,Cr)2C-7%Ni gehört zu den kommerziell verfügbaren Standardzusammensetzungen für Hartmetallspritzpulver und -schichten. Abweichend davon wird sie mit unterschiedlichen Bezeichnungen wie WC-“CrC“-Ni, WC-Cr3C2-Ni oder WC-NiCr gehandelt. In diesem Beitrag werden die spezifischen Mikrostrukturen und Phasenzusammensetzungen der Beschichtungspulver und der HVOF-gespritzten Schichten vorgestellt. Das besondere Anliegen ist es, dass noch unbekannte Potenzial dieser Zusammensetzung, ihre außerordentliche Oxidationsstabilität und das günstige Verhalten im ungeschmierten Reib-/Gleitverschleiß aufzuzeigen. Diese Eigenschaften werden mit denen von WC-10%Co-4%Cr-Schichten verglichen. Da seit dem Zeitpunkt der Entwicklung der Zusammensetzung 50 Jahre verstrichen sind, kann davon ausgegangen werden, dass sie bei weitem nicht optimal auf die uns heute zur Verfügung stehende Anlagentechnik abgestimmt ist. Somit ist der Impuls für weitere Verbesserungen und neue Anwendungen gegeben. The composition WC-(W,Cr)2C-7%Ni is a standard commercially available composition for hardmetal feedstock powders and coatings, but it is sold under a variety of designations including WC-'CrC'-Ni, WC-Cr3C2-Ni and WC-NiCr. In this paper the specific microstructures and phase compositions of the feedstock powder and the HVOF-sprayed coatings are presented with a view to shedding light on the still-unknown application potential of this composition as well as its extraordinary oxidation resistance and advantageous behaviour in dry sliding conditions. These properties are compared with those of WC-10%Co-4%Cr coatings. As 50 years have passed since it was developed, this composition can well be said to be far from optimal for today’s HVOF equipment. There is hence room for improvement as well as for new applications. KW - Thermal spraying KW - Dry sliding KW - High temperature KW - APS KW - HVOF KW - WC KW - Ni KW - (W,Cr)2C KW - Dry friction PY - 2008 SN - 1866-6248 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 1 SP - 37 EP - 40 PB - DVS-Verl. CY - Düsseldorf AN - OPUS4-17465 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Berger, L.-M. A1 - Saaro, S. A1 - Woydt, Mathias T1 - WC-(W,Cr)2C-Ni - die unbekannte Hartmetallschicht / WC-(W,Cr)2C-Ni - the unknown hardmetal coating JF - Thermal spray bulletin N2 - Die Zusammensetzung WC-(W,Cr)2C-7%Ni gehört zu den kommerziell verfügbaren Standardzusammensetzungen für Hartmetallspritzpulver und -schichten. Abweichend davon wird sie mit unterschiedlichen Bezeichnungen wie WC-'CrC'-Ni, WC-Cr3C2-Ni oder WC-NiCr gehandelt. In diesem Beitrag werden die spezifischen Mikrostrukturen und Phasenzusammensetzungen der Beschichtungspulver und der HVOF-gespritzten Schichten vorgestellt. Das besondere Anliegen ist es, dass noch unbekannte Potenzial dieser Zusammensetzung, ihre außerordentliche Oxidationsstabilität und das günstige Verhalten im ungeschmierten Reib-/Gleitverschleiß aufzuzeigen. Diese Eigenschaften werden mit denen von WC-10%Co-4%Cr-Schichten verglichen. Da seit dem Zeitpunkt der Entwicklung der Zusammensetzung 50 Jahre verstrichen sind, kann davon ausgegangen werden, dass sie bei weitem nicht optimal auf die uns heute zur Verfügung stehende Anlagentechnik abgestimmt ist. Somit ist der Impuls für weitere Verbesserungen und neue Anwendungen gegeben. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- The composition WC-(W,Cr)2C-7%Ni is a standard commercially available composition for hardmetal feedstock powders and coatings, but it is sold under a variety of designations including WC-'CrC'-Ni, WC-Cr3C2-Ni and WC-NiCr. In this paper the specific microstructures and phase compositions of the feedstock powder and the HVOF-sprayed coatings are presented with a view to shedding light on the still-unknown application potential of this composition as well as its extraordinary oxidation resistance and advantageous behaviour in dry sliding conditions. These properties are compared with those of WC-10%Co-4%Cr coatings. As 50 years have passed since it was developed, this composition can well be said to be far from optimal for today’s HVOF equipment. There is hence room for improvement as well as for new applications. KW - Thermal spraying KW - Dry sliding KW - High temperature KW - APS KW - HVOF KW - WC KW - Ni KW - (W,Cr)2C KW - Dry friction PY - 2008 SN - 1866-6248 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 1 IS - 1 SP - 37 EP - 40 PB - DVS-Verl. CY - Düsseldorf AN - OPUS4-31745 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Berger, L.-M. A1 - Stahr, C.C. A1 - Saaro, S. A1 - Thiele, S. A1 - Woydt, Mathias A1 - Kelling, Norbert T1 - Dry sliding up to 7.5m/s and 800°C of thermally sprayed coatings of the TiO2-Cr2O3 system and (Ti,Mo)(C,N)-Ni(Co) JF - Wear KW - Dry sliding KW - High-temperature KW - Magnéli-phase KW - TiO2 KW - Cr2O3 KW - Coating PY - 2009 DO - https://doi.org/10.1016/j.wear.2008.12.105 SN - 0043-1648 VL - 267 IS - 5-8 SP - 954 EP - 964 PB - Elsevier CY - Amsterdam AN - OPUS4-19459 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dmitriev, A. I. A1 - Österle, Werner A1 - Kloß, Heinz A1 - Orts-Gil, Guillermo T1 - A study of third body behaviour under dry sliding conditions. Comparison of nanoscale modelling with experiment JF - Estonian Journal of Engineering N2 - Automotive brake pads consist of many components but it is still not entirely clear which role each of the elements of this complex composition plays to provide the specified regimes of sliding. This is due to the mutual interaction of multiscale mechanisms, realized during the friction. In this work we have attempted to partly answer this question using computer simulations. Since the simulation allows us to consider various combinations of the structure of the system being simulated ceteris paribus, it becomes possible to understand the role of each constituent sequentially. The main attention is paid to the structure and composition of the thin film that forms on the surface of both bodies as a result of compaction of the wear product, its chemical composition and oxidation. This layer, also named a third body or friction film, differs in composition and microstructure from the two first bodies. We considered a single contact for the steady state sliding when the structure and composition of friction films already are formed. As a modelling tool we used the method of movable cellular automata, which has well proven itself in solving of such tasks. We investigated the influence of modification of the structure and composition of the third body on the features of system behaviour at friction. To assess the adequacy of the numerical model, experimental studies with an artificial third body were also carried out. The Simulation results are in good agreement with experimental data. KW - Third body KW - Dry sliding KW - Mechanically mixed layer KW - Computer simulation PY - 2012 DO - https://doi.org/10.3176/eng.2012.3.12 SN - 1736-6038 SN - 1736-7522 VL - 18 IS - 3 SP - 270 EP - 278 AN - OPUS4-38545 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kaltzakorta, O. A1 - Wäsche, Rolf A1 - Hartelt, Manfred A1 - Aginagalde, A. A1 - Tato, W. T1 - Influence of polymer filler on tribological properties of thermoplastic polyurethane under oscillating sliding conditions against cast iron JF - Tribology letters N2 - The tribological behaviour of unfilled thermoplastic polyurethane (TPU) and a polymer sphere filled (TPUG) thermoplastic polyurethane have been studied under oscillating sliding condition against cast iron as a counterpart. In the case of unfilled TPU, the wear mechanisms are dominated by particle detachment and roll formation. In principle, TPUG also showed a similar wear mechanism as that of unfilled TPU; in addition, particle pull-out and delamination are also observed. Wear volume of TPUG was significantly higher than that for the unfilled TPU and this is attributed to the different material removal processes taking place in the material during sliding. The polymer spheres as a filler material deteriorated the wear resistance of TPU because of improper adhesion and bonding of filler in the TPU matrix and therefore it contributed to more wear. In case of TPU the friction behaviour was strongly dependant on the temperature and surface roughness of the counter body. The results showed that below the glass transition temperature higher friction values are observed with higher counter body surface roughness. However, above the glass transition temperature, higher friction values are observed with a smoother surface roughness of the counter body. In case of TPUG, the friction behaviour was not significantly dependent on surface roughness of the counter body. KW - Dry sliding KW - Polymers KW - Cast iron KW - Temperature PY - 2012 DO - https://doi.org/10.1007/s11249-012-0017-6 SN - 1023-8883 SN - 1573-2711 VL - 48 IS - 2 SP - 209 EP - 216 PB - Springer Science Business Media B.V. CY - Dordrecht AN - OPUS4-27272 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wallstabe, Ronald T1 - Laser-assisted surface modification of alumina and its tribological behavior JF - Journal of materials engineering and performance N2 - High performance friction systems, e.g., dry clutches and brakes, require a good wear resistance and a friction coefficient that is nearly independent from sliding velocity and environmental conditions. Organic-based friction materials have reached their limitations regarding higher power densities. Engineering ceramics such as alumina (Al2O3) or silicon carbide (SiC) offer a great potential since remarkably higher thermal and mechanical loading is possible. However, the tribological performance of these monolithic ceramics is still insufficient. The aim of the present study was to assess the potential of a laser-assisted surface modification process in order to improve the tribological performance with regard to the application in dry friction systems. Therefore, commercially available alumina was modified using a newly developed laser-assisted preheating process and subsequent melting of the ceramic’s surface using a CO2-laser and modification by additives such as TiC, TiN, B4C, WC, ZrB2, Cr, Ni, Cu, and Ti. A systematic variation of additives and process parameters led to different multiphase microstructures. Subsequently, these were characterized using scanning electron microscopy and surface analysis methods (wavelength dispersive X-ray spectroscopy, energy dispersive X-ray spectroscopy). Finally, the tribological properties were investigated using a laboratory tribometer. The surface-modified ceramics were tested in unidirectional sliding motion against steel disks. The tribological results of the surface-modified ceramics were compared to those of monolithic Al2O3 and SiC ceramics and showed a reduced dependence of friction coefficient on sliding velocity. Moreover, the multi-phase ceramics possessed a higher wear resistance than the monolithic ones. KW - Alumina KW - Ceramics KW - Ceramic matrix composites KW - Dry sliding KW - Laser-assisted surface modification KW - Steel KW - Tribology KW - Wear resistance PY - 2012 DO - https://doi.org/10.1007/s11665-012-0215-2 SN - 1059-9495 SN - 1544-1024 SP - 1 EP - 13(?) PB - ASM international CY - Materials Park, Ohio AN - OPUS4-25842 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wäsche, Rolf A1 - Hartelt, Manfred A1 - Springborn, U. A1 - Bewilogua, K. A1 - Keunecke, M. T1 - Wear of carbon nitride coatings under oscillating sliding conditions JF - Wear N2 - An extended study on tribological properties of carbon nitride coatings under oscillating sliding conditions has been carried out. The coatings were prepared by reactive magnetron sputtering with graphite target using nitrogen as reactive gas in an argon/nitrogen atmosphere during the deposition process to deposit carbon nitride, CNx. Coating thickness was about 2 µm. A 200–300 nm thick Ti interlayer was used to enhance adhesion. The nitrogen flow during the deposition was varied to control the amount of nitrogen in the coating. Maximum amount of N-content was about 28 at%, achieved at a maximum N2 flow rate. Other deposition parameters were target to substrate distance, substrate temperature during deposition and bias voltage. The results show a large variation of hardness depending mainly on the nitrogen content and bias voltage. Higher bias voltage produced harder coatings as did lower nitrogen content. The tribological properties were tested unlubricated and lubricated by paraffin oil under gross slip fretting conditions at room temperature against alumina as counter material. Most coatings, but not all, showed a more or less pronounced dependence of wear on relative humidity with wear rates from 10-5 to 10-6 mm3/Nm. The best coatings with regard to a low wear rate and the least dependence upon relative humidity were carbon nitride coatings deposited at elevated substrate temperatures up to 350 °C. The wear resistance of these coatings was increased under the most severe conditions by about one order of magnitude. The results are discussed on the basis of a transfer layer formation. The results show clearly that wear is not significantly correlated to the coating hardness which itself is strongly dependant on the nitrogen content. However, under lubricated conditions with paraffin oil, wear rates were generally very low with wear coefficients at about 10-8 mm3/Nm. KW - Carbon nitride KW - Wear KW - Fretting KW - Dry sliding KW - Paraffin oil PY - 2010 DO - https://doi.org/10.1016/j.wear.2010.08.010 SN - 0043-1648 VL - 269 IS - 11-12 SP - 816 EP - 825 PB - Elsevier CY - Amsterdam AN - OPUS4-22208 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -