The Nordic Symposium on Tribology (NordTrib) is held biennially in one of the Nordic countries: Finland, Sweden, Norway and Denmark. During the years the symposium has grown and it is now much larger ...and more international than it was in 1984. The 17th NordTrib Symposium (Nortrib 2016) was organized in Aulanko, Haxneenlinna, Finland, June 14th-17th, 2016 by the Finnish Society for Tribology and VTT Technical Research Centre of Finland Ltd.
Bsub.4C-particle-reinforced Al (Bsub.4Csub.p/Al) composites are widely used in various areas, e.g., armors, electronic packaging and fuel storage, owing to their several outstanding properties ...including high specific rigidity, excellent wear resistance and light weight. Selective laser melting (SLM) is favored in manufacturing complex components because of its high raw material utilization rate and high efficiency. In this work, a Bsub.4Csub.p/Al composite was successfully synthesized by SLM, and the effects of one of the most important parameters, scanning speed (100-700 mm/s), on the phase composition, density, microhardness and tribological properties of the samples were investigated. The microhardness, relative density and dry-sliding wear resistance of as-prepared Bsub.4Csub.p/Al composites were improved with the decrease in scanning speed, and the sample fabricated at a scanning speed of 100 mm/s exhibited a relative density as high as about 97.1%, and a maximum microhardness of ~180 HVsub.0.1 (approximately six times more than that of the SLM-formed pure Al sample, 31 HVsub.0.1), a minimum wear rate of 4.2 × 10sup.−5 mmsup.3·Nsup.−1·msup.−1 and a corresponding friction coefficient of 0.41. In addition, abrasive wear, adhesive wear and oxidation wear were found to be behind the overall wear behavior of as-prepared Bsub.4Csub.p/Al composites.
Titanium dioxide (TiOsub.2), by its tribological behavior, is known as a solid lubricant. TiOsub.2 as a solid lubricant, together with tungsten disulfide (WSsub.2) and molybdenum disulfide (MoSsub.2) ...decreases friction and excessive wear. By compacting TiOsub.2 powder, pellets are formed. Studies and research on the solid lubricant coatings were conducted with success on a tribometer with the possibility of making two simultaneous contacts, pellet/disk, and slider pad/disk. On the disk of a tribometer, we studied the lubrication characteristics of the TiOsub.2 powder particles as the third body by intentionally transferring. Results show that the TiOsub.2 pellet behaved like an effective oil-free lubricant by self-repairing and self-replenishing. In experiments, a TiOsub.2 pellet is intentionally sheared against the surface of the disk, while the slider pad slips loaded on the lubricated surface until the deposited powder film is exhausted. A theoretical model control volume fractional coverage (CVFC) was used to estimate both the wear rate for the lubricated pellet/disk sliding contact and the friction coefficient at the pad/disk separation surface. According to materials properties, disk velocity, pellet and slider pad load, the pellet wear rate, and slider pad friction coefficient, using the CVFC model, can establish the pellet wear rate, and slider pad friction coefficient. The fractional coverage represents a parameter of the CVFC model that varies with time, and it is useful for estimating the film amount from the third body that covers the disk asperities. Model results well enough describe the tribological behavior of the sliding contacts in experiments, both qualitatively and quantitatively. In addition, the theoretical results obtained by modeling and the experimental those obtained in the process of friction, are compared.
WC -10Co4Cr-5% B.sub.4C, -10% B.sub.4C, and -15% B.sub.4C coatings were fabricated on Cr12MoV steel by laser cladding (LC) to improve its wear resistance. The effect of B.sub.4C mass fraction on the ...phases, morphologies, and chemical elements of obtained coatings were investigated using an X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS), respectively, and the tribological performance was evaluated using a ball-on-disk tester. The results show that the average COFs and wear rates of WC-10Co4Cr-5% B.sub.4C, -10% B.sub.4C, and -15% B.sub.4C coatings are increased with the increase in B.sub.4C mass fraction, and the WC-10Co4Cr-5% B.sub.4C coating has the best wear resistance among the three kinds of coatings, which is attributed to the effects of grain refinement and solid solution strengthening. The excessive B.sub.4C particles cause a large decomposition of WC, and the coating microstructure becomes coarse when the B.sub.4C mass fraction exceeds 5%, which results in the tribological performance decreasing. Moreover, the wear mechanism of WC-10Co4Cr-5% B.sub.4C and -10% B.sub.4C coatings is abrasive wear, while that of WC-10Co4Cr-15% B.sub.4C coating is abrasive wear and adhesive wear.
The materials tribology community has identified that the transfer film attached to the surface of the counterpart metal during the friction process is not only closely related to the filler ...modification material but also a key factor affecting the tribological properties of polymer composites; however, there is a lack of feasible methods to quantify the characteristics of the transfer film. In this study, Nano-ZrOsub.2 and polyetheretherketone (PEEK) were filled into a PTFE matrix in order to enhance the wear resistance of polytetrafluoroethylene (PTFE). The tribological properties of the modified PTFE composites were tested using a linear reciprocating friction and wear tester, and the entire friction experiment was designed in seven separate stages. Morphological features were extracted and analyzed from photographs of the transfer film acquired by optical microscopy at each friction stage using an image processing program. The thickness and roughness of the transfer film sections were measured using a non-contact profilometer. Abrasive debris were collected, and their morphological features were observed with an electron microscope. The results showed that the synergistic addition of soft PEEK and hard Nano-ZrOsub.2 particles effectively inhibited interlayer slippage between PTFE molecular chains, dramatically reducing the size and yield of abrasive debris, and facilitated the improvement of the thickness and firmness of the transfer film, which significantly enhanced the wear resistance of the PTFE composites (the lowest volumetric wear rate for Nano-ZrOsub.2/PEEK/PTFE was only 1.76 × 10sup.−4 mmsup.3/Nm). Quantitative analyses of the morphological characteristics of the transfer films revealed that the coverage and roundness of the transfer films gradually increase with the friction stroke, while the aspect ratio and texture entropy subsequently decrease gradually. The coverage, area, mean, third-order moments, and consistency of the transfer film strongly correlated with the volumetric wear rate (correlation coefficient |r| > 0.9).
Two-dimensional covalent organic frameworks (2D COFs) are an emerging class of crystalline porous materials formed through covalent bonds between organic building blocks. COFs uniquely combine a ...large surface area, an excellent stability, numerous abundant active sites, and tunable functionalities, thus making them highly attractive for numerous applications. Especially, their abundant active sites and weak interlayer interaction make these materials promising candidates for tribological research. Recently, notable attention has been paid to COFs as lubricant additives due to their excellent tribological performance. Our review aims at critically summarizing the state-of-art developments of 2D COFs in tribology. We discuss their structural and functional design principles, as well as synthetic strategies with a special focus on tribology. The generation of COF thin films is also assessed in detail, which can alleviate their most challenging drawbacks for this application. Subsequently, we analyze the existing state-of-the-art regarding the usage of COFs as lubricant additives, self-lubrication composite coatings, and solid lubricants at the nanoscale. Finally, critical challenges and future trends of 2D COFs in tribology are outlined to initiate and boost new research activities in this exciting field.
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•Evolution of 2D COF synthesis and their resulting properties is summarized.•Strategies for COF thin film preparation are critically discussed.•State-of-the-art tribological performance of COFs are holistically reviewed.•Challenges and prospects of COFs are outlined to promote their development in tribology.
Upgrading and developing metallic materials are bases for improving the performance of aircraft. As one of the new structural metallic materials used in aerospace, lightweight and high-strength ...γ-TiAl alloys have been successfully used as high-risk structural parts in aircraft engines. Nonetheless, intrinsic embrittlement is the main factor limiting applications of γ-TiAl alloys. To further enlarge the application fields of γ-TiAl alloys, it is urgent to improve mechanical properties, like strength and ductility. This paper first introduces phase constituents and precipitates of γ-TiAl alloys, summarizes microstructure control measures of γ-TiAl alloys, and presents texture evolutions of γ-TiAl alloys. Then, based on four strength mechanisms, this review paper summarizes factors influencing mechanical properties of γ-TiAl alloys during compression, tension, creep and fatigue as well as tribology tests. It also includes the fracture mechanisms of γ-TiAl alloys. Finally, this paper proposes some future development directions for studying γ-TiAl alloys, like screening chemical compositions via machine learning technology, and developing microstructure evaluation software.
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Using simulation of contact interaction of rough surfaces, it is possible to determine the dependence of the convergence value on the load applied to the conjugate surfaces, which will allow more ...accurately solve tribological problems, as well as problems of ensuring a given degree of tightness, etc.
NiP coatings produced by electrodeposition have important mechanical, tribological and electrochemical properties. They can also exhibit catalytic activity and beneficial magnetic behaviour. With ...subsequent thermal treatment, the hardness of such NiP coatings can approach or exceed that of hard Cr coatings. Electrochemical codeposition of homogeneously dispersed second phase particles within the NiP matrix can enhance deposit properties and meet the challenging demands on modern engineering coatings. A general overview of research work on the electrodeposition of NiP composite coatings containing included ceramic or solid lubricant particles is provided. Advances in research into NiP composite layers reinforced by SiC, B4C, WC, Al2O3, SiO2, TiO2, CeO2, MWCNT, MoS2, WS2, TiN, hexagonal BN, PTFE and their combinations are considered. Major models proposed for the codeposition of particles, the influence of bath hydrodynamics and control of operational parameters are illustrated by examples. Important trends are highlighted and opportunities for future R & D are summarised.
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•The electrodeposition of Ni-P coatings containing included particles is reviewed.•Substrate, reactions, bath composition/additives and flow are important.•Developments include pulse plating and nanostructured particle deposits.•Expanding application areas include tribology and corrosion protection.•Aspects deserving further R & D are identified.
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