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- Lindquist, Mattias, et al.
(författare)
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Tribofilm formation and tribological properties of TiC and nanocomposite TiAlC coatings
- 2009
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 266:3-4, s. 379-387
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Tidskriftsartikel (refereegranskat)abstract
- In a recent work a concept for self lubricating low friction TiC and nanocomposite TiAlC coatings was developed. Here we further investigate the mechanical and tribological properties of these coatings. Under identical deposition conditions, the addition of Al initiates the formation of a nanocomposite consisting of (Ti,Al)C grains in an amorphous carbon matrix. The coefficient of friction is lowered from 0.2 to below 0.1 in a pin-on-disc test against steel with unaffected coating wear rate. The lower friction is attributed to a more extensive formation of amorphous carbon and graphitisation on both the counter surface and in the coating wear track. The addition of Al also reduces coating hardness, Young's modulus and the residual stress, which can be explained by the weak carbide-forming ability of Al and the formation of a nanocomposite microstructure.
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- Lindquist, Mattias, et al.
(författare)
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Tribofilm formation from TiC and nanocomposite TiAlC coatings, studied with Focused Ion Beam and Transmission Electron Microscopy
- 2009
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 266:9-10, s. 988-994
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Tidskriftsartikel (refereegranskat)abstract
- This work demonstrate how two different carbide coatings respond very differently to tribological stress and their very different ability to provide low friction tribofilms in dry sliding against steel. Both coatings, TiC and TiAlC, were deposited by DC-magnetron sputtering, but while the TiC is a thermodynamically stable coating, the TiAlC is made metastable with the addition of Al, and therefore releases carbon upon tribological testing. Thus, the TiAlC coating is shown to be self-lubricating on the atomic scale which makes very low friction achievable. The primary interest in this study is the differences in the tribofilms formed on the steel balls that have been sliding against the two coatings. Cross-section samples for transmission electron microscopy were extracted from the ball tribofilms using a focused ion beam instrument. X-ray photoelectron spectroscopy and Raman analysis were employed to provide information on the chemical and structural characteristics of the tribofilms. It was shown that tribofilms on steel balls largely inherit the structure and composition that evolve in the coating wear tracks, that the tribofilm microstructure greatly affects the friction level. It was also shown that tribofilm delamination, occurring with tribofilm growth, was initiated in weak ribbon like regions inside the tribofilm.
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- Wilhelmsson, Ola, et al.
(författare)
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Deposition and characterization of magnetic Ti–Fe–C nanocomposite thin films
- 2010
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Ingår i: Thin Solid Films. - : Elsevier B.V.. - 0040-6090 .- 1879-2731. ; 518:10, s. 2607-2616
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite (Ti1−xFex)Cy films with different compositions have been deposited by dc magnetron sputtering at 450 °C. The sputtered films could dissolve as much as 20–30 at.% of Fe on the Ti sites which is far above the maximum solid solubility at equilibrium. The solubility was dependent on the carbon content and more carbon-rich films could dissolve more Fe without the formation of Fe-precipitates. The addition of Fe also reduced the grain size of the carbide particles. Upon annealing, α-Fe starts to precipitate and the amount and size of these precipitates can be controlled by the annealing procedure and from the total composition of the as-deposited films. Mechanical and tribological studies show that some compositions of the (Ti1−xFex)Cy films have very good wear-resistant properties. These results together with magnetization measurements suggest that Ti–Fe–C films can be used as a wear-resistant magnetic thin film material.
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- Wilhelmsson, Ola, et al.
(författare)
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Design of Nanocomposite Low-Friction Coatings
- 2007
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 17:10, s. 1611-1616
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Tidskriftsartikel (refereegranskat)abstract
- Friction and wear between moving surfaces is unavoidable and is an important reason for failure of mechanical components. A wear-resistant and low-friction coating can prolong the lifetime of an engineered component. Here we demonstrate a new concept for the design of low-friction nanocomposite carbide coatings with an intrinsic driving force to form amorphous carbon (C-C bonds). Ti-Al-C has been chosen as a model system, but the idea is general and should be applicable to a wide class of materials. The ability to intrinsically form amorphous carbon is achieved by a substitutional solid solution of the weak-carbide-forming metal (Al) into the thermodynamically stable monocarbide (TiC). This creates, in a controllable manner, a driving force for phase separation of carbide particles embedded in a matrix of amorphous carbon. In a tribological contact the amorphous carbon can be further graphitized and thereby lower the friction coefficient. Consequently, the model system has a self-lubricating mechanism but at the same time a tunable share of the two phases, which gives excellent possibilities to design wear resistance and toughness. In this paper we show that the friction coefficient can be lowered by more than 50 % for Al-containing TiC coatings without severe loss in mechanical characteristics.
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