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Direct laser interference patterning of tetrahedral amorphous carbon films for tribological applications

 
: Roch, T.; Weihnacht, V.; Scheibe, H.-J.; Roch, A.; Lasagni, A.F.

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Diamond and Related Materials 33 (2013), pp.20-26
ISSN: 0925-9635
English
Journal Article
Fraunhofer IWS ()
diamond-like carbon; laser material; laser modification; radiation induced effects; tribology

Abstract
In this work, the influence of surface topography and micro structural changes on the tribological properties of tetrahedral amorphous carbon coatings (ta-C) structured using a holographic technique the direct laser interference pattering (DLIP) is investigated. By utilizing a nanosecond pulsed UV-laser (wavelength 355 nm), both ablation and graphitization thresholds were determined as a function of the pulse number. Incubation effects for the ablation threshold (~ 205 mJ cm- 2) were found to be negligible. However, for the graphitization of the film thresholds varying from 47 to 74 mJ cm - 2 were observed depending on the number of laser pulses utilized (from 1 to 30) and thus obtaining an incubation factor of 1.13. Using two- and three-beam interference setups, dot- and line-like periodi c arrays were fabricated. The tribological performance of these patterns was investigated under reciprocating sliding with a ball on disk method under non-lubricated conditions showing that coefficient of friction can be reduced from ~ 0.089 (un-patterned) to ~ 0.055 patterned ta-C (~ 30% reduction). The results can be explained based on the reduction of surface contact area combined with high hardness as well as the good intrinsic tribological properties of the ta-C films.

: http://publica.fraunhofer.de/documents/N-227994.html