Tribological properties of a-C:H:Al coatings

Abstract : Hydrogenated amorphous carbon (a-C:H) thin films are among the best coating solutions for the reduction of automotive fuel consumption because of its very good tribological properties. Friction losses are indeed the main source of energetic consumption in an automotive engine. 80 % of friction occurring in the valve train system is only due to the cam-tappet contact, representing 20 % of the total losses in the engine. That is why the reduction of friction coefficient in dry and lubricated conditions is still in demand. Quite high values for hardness are also required to withstand the severity of this contact. Many metallic elements have been introduced in the DLC (Diamond-Like Carbon) matrix to modify their tribological properties. In particular, elements which are not able to form carbide phases like Al enable to benefit from doping without altering the matrix properties. For Al-DLC, a decrease in friction can be achieved in dry conditions with a friction coefficient of 0.02 for a DLC containing less than 17.6 at. % Al, while pure DLC exhibits a friction coefficient of 0.11. But a more severe wear for Al-DLC than pure a-C:H is also observed [1]. The objective of this work is thus to obtain a-C:H:Al with lower friction than standard a-C:H keeping a high level of wear resistance. Al-DLC films are produced by a hybrid PECVD - magnetron sputtering process using different power on the Al target to explore various Al/C ratios. X-ray photoelectron spectroscopy is performed to determine the chemical composition of the films and the structure is observed by Raman spectroscopy. Then hardness and Young’s modulus are measured by nanoindentation. To conclude, tribological tests are performed with an alternative ball-on-disc tribometer to measure wear resistance and friction coefficient in dry and lubricated conditions with various lubricants containing additives designed to react with Al. [1] Dai W. et al., 2011, J. Alloys Compd., 509(13), pp.4626–4631.
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Contributeur : Cédric Jaoul <>
Soumis le : lundi 5 janvier 2015 - 17:02:36
Dernière modification le : mercredi 14 février 2018 - 16:29:44

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  • HAL Id : hal-01100026, version 1

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Laureline Kilmann, Cédric Jaoul, Maggy Colas, Christelle Dublanche-Tixier, Pascal Tristant, et al.. Tribological properties of a-C:H:Al coatings. Plasma Surface Engineering, Sep 2014, Garmisch-Partenkirchen, France. ⟨hal-01100026⟩

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