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Diamond - like carbon coatings for tribological applications

This paper presents studies on the morphology, mechanical and tribological properties of hydrogen-free diamond-like carbon (DLC) coatings deposited via magnetron sputtering under different bias voltages. Atomic force microscope (AFM), transmission electron microscope (TEM), Raman spectroscopy, nano-indentation and ball-ondisc tribotest were employed to characterize the deposited coatings. Diamond-like carbon coatings had very smooth surface with the roughness (Ra) of less than 3.5 nm (for 1.2 mm - thick coatings on Si wafer). Under high bias voltage, superhard coatings with hardness of more than 30 GPa were obtained. | Science & Technology Development, Vol 11, No.10 - 2008 DIAMOND - LIKE CARBON COATINGS FOR TRIBOLOGICAL APPLICATIONS Bui Xuan Lam University of Groningen, the Netherlands (Manuscript Received on November 28th, 2007, Manuscript Revised June 27th, 2008) ABSTRACT: This paper presents studies on the morphology, mechanical and tribological properties of hydrogen-free diamond-like carbon (DLC) coatings deposited via magnetron sputtering under different bias voltages. Atomic force microscope (AFM), transmission electron microscope (TEM), Raman spectroscopy, nano-indentation and ball-ondisc tribotest were employed to characterize the deposited coatings. Diamond-like carbon coatings had very smooth surface with the roughness (Ra) of less than 3.5 nm (for 1.2 µm thick coatings on Si wafer). Under high bias voltage, superhard coatings with hardness of more than 30 GPa were obtained.The self-lubrication mechanism of diamond-like carbon combined with smooth surface resulted in very low coefficients friction of less than 0.15. Magnetron sputtered diamond-like carbon show a big potential for tribological applications, especially, under dry or poorly lubricated conditions. Keywords: magnetron sputtering, diamond-like carbon, bias voltage, hardness, roughness, tribology, graphitization 1. INTRODUCTION Carbon is one of the commonest elements throughout the Universe. The electronic configuration of carbon is written as 1s22s22p2. In the nature carbon is found as diamond, graphite and amorphous carbon. The name diamond-like carbon was first coined by Sol Aisenberg in 1971 to describe the hard carbon films that he prepared by direct deposition from low energy carbon ion beams [1]. Now, diamond-like carbon (DLC) is the name commonly accepted for hard carbon coatings which have similar mechanical, optical, electrical and chemical properties to natural diamond, but which do not have a dominant crystalline lattice structure. They are amorphous and consist of a mixture of sp3 (diamond) .