Friction and wear reducing layers

Nanoscale solid films are important for space technology as friction and wear-reducing layers, e.g. for the development of MEMS components. As determining factors for the tribological characteristics of materials their relative hardness, fatigue resistance as well as the kind and strength of the chemical bondings should be mentioned. Important in this context

Tribology in space dif are intermediate layers (lubricants, coverage layers, oxide and reaction fers strongly from terrestrial conditions layers) between the friction partners, which behave in space (high vacuum) significantly different than under terrestrial conditions.

As solid lubricants and mechanical protection coatings for space components in principle chalcogenides (MoS2, WS2, etc.), chalcogenide composites, carbides (WC, TiC, etc.), nitrides (e. g. TiN, BN) as well as carbon materials should be taken into consideration. The illustration 12 gives an overview of the relation of hardness and friction coefficients in different material classes. Carbon materials such as diamond and Diamor (ta-C) exhibit both a large hardness and small friction coefficient. By means of nanostructuring an improved adhesion of the carbon layers on the substrate can be obtained. For space applications it has to be taken into account however, that the tribological behaviour under space conditions (high vacuum) differs strongly in comparison to terrestrial conditions.

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Diamond <— increasing smoothness ta-c a-c:H

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