Tribological Carbon-based Coatings for Wear Protection
Publication from Materials
Proc. Materials Week, 30 September - 2 October, Munich, Paper No. 679, 10/2002
The aim of the present work is the investigation of the structural, mechanical and tribological properties of low-wear Diamond-Like Carbon (DLC) coatings for industrial applications. Amorphous hydrogen-free (a-C) and hydrogenated (a-C:H) DLC coatings were coated onto various steel substrates (AISI 1045H, B7, H13, D2, M2) with hardness levels varying from 28 to 66 HRC by employing the Pulsed Laser Deposition (PLD) method. Therefore graphite targets were ablated with the 1064 nm wavelength of a Nd:YAG laser in argon and C2H2 atmospheres. The high mean laser power of the applied PLD equipment guarantees deposition rates competitve to other physical vapour deposition (PVD) techniques. Because of the specific process conditions and the use of pure titanium adhesive interface layers, coatings with high adhesion to the substrate were produced at room temperature. The investigations of the coatings by means of light and scanning electron microscopy reveal the high surface quality and extremely dense coating structures. XRD measurements indicate the amorphous structure of the coatings. The nature of the chemical bonding was examined by XPS indicating different amounts of sp3 carbon bonds. Pin-on-disc tests against 100Cr6 ball-bearing steel balls as counterparts show excellent wear resistance of a-C and a-C:H DLC coatings on all different steel substrates. The results demonstrate the applicability of PLD DLC coatings for wear protection of high precision components in the field of tools and mechanical components.