Title: Influence of humidity on the tribological behaviour of W-alloyed C-based amorphous coatings

Authors: Carlos Wagner Moura e Silva; José Roberto Tavares Branco; Albano Cavaleiro

Addresses: Centro Federal de Educação Tecnológica de Minas Gerais, 36.700-000, Leopoldina, Minas Gerais, Brazil. ' Fundação Centro Tecnológico de Minas Gerais, 31.170-000, Belo Horizonte, Minas Gerais, Brazil. ' Department of Mechanical Engineering, University of Coimbra, 3.030-788 Coimbra, Portugal

Abstract: The frictional behaviour of diamond-like carbon (DLC) coatings depends on either their chemical composition or the humidity ratio in the testing environment. In this research, C-based amorphous coatings were deposited with W addition of ?10% in reactive and non-reactive atmosphere, in an unbalanced magnetron apparatus. Reactive deposited coatings have approximately 29% H. Both coatings have hardness of 12 GPa and the scratch test critical load values were higher than 60 N. The coatings were tribological tested on a pin-on-disk machine under standard conditions and different relative humidity (RH %) of 30%, 50% and 80%. Both coatings showed the same frictional trend, i.e., friction coefficient increased with RH % value but, globally, H-containing films have lower friction than non-hydrogenated ones ([0.01-0.05] and [0.05-0.20]), respectively. Raman analysis of the worn tracks showed, in both cases, an increase of the G/D ratio of the two main characteristic peaks (G and D) of sputtered C-based coatings.

Keywords: diamond-like carbon coatings; W-DLC: H coatings; tungsten alloyed hydrogenated DLC coatings; low friction; tribological behaviour; tribology; humidity ratio; friction coefficient.

DOI: 10.1504/IJSURFSE.2011.044276

International Journal of Surface Science and Engineering, 2011 Vol.5 No.4, pp.261 - 271

Available online: 14 Dec 2011 *

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