International Tribology Council The 8 th International Conference BALTTRIB'2015 Aleksandras Stulginskis University 26–27 November 2015 Lithuanian Scientific Society Department „Tribologija" Akademija, Kaunas, Lithuania Proceedings of BALTTRIB’2015 edited by prof. J. Padgurskas eISSN 2424-5089/eISBN 978-609-449-093-4 DOI: 10.15544/balttrib.2015.12 Copyright © 2015 The Authors. Published by Aleksandras Stulginskis University. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. TRIBOLOGICAL PROPERTIES OF SPUTTER DEPOSITED CARBON- COPPER COMPOSITE FILMS A.Leitans † , N.Bulaha, J.Lungevics Institute of mechanical engineering, Riga Technical University, Latvia Abstract: Carbon-copper composite coatings were deposited using high power magnetron sputtering technique. Tribological tests were performed using ball-on-disk type tribometer. Friction coefficient and wear rate were determined at 40 N load. It was found that an increase in the percentage composition of carbon in C-Cu coating, reduces the coefficient of friction value. But at higher concentrations of C coating it becomes more brittle, that reduces wear resistance. Keywords: nanocoatings, magnetron sputtering, carbon-copper composite 1. INTRODUCTION Many enterprises that specialize in mechanical engineering are confronted with short life span of equipment and instruments that leads to high maintenance costs and low productivity. Friction causes the wear of machinery, accelerates decay of moving parts and decreases performance of instruments. Thus, decreasing of coefficient of friction (CoF) is necessary for low-cost, durable and energy- efficient machinery. Physical vapour deposition magnetron sputtering technique [1], which does not affect the properties of the base material and biochemical functionality, is used for depositing tribological coatings for friction reduction and wear resistance. Such coatings have good adhesion and serve as a protective layer. Carbon-copper (a-C/Cu) coatings are in particular interest [2-4]. Such coatings have composite structure in which copper and graphite do not constitute carbide directly - copper nanoparticles are built in graphite matrix. a-C/Cu coatings are characterized with high mechanical and tribological quality index [5], therefore, the present article researches these nanocoatings, aiming at obtaining the coefficient of surfaces with a low friction and, in compliance with it, the wear resistance. 2. EXPERIMENTAL 2.1. Preparing substrates for deposition experiment The substrate material is 31 mm dia. x 5mm carbon steel C45 (DIN, EN) plates were used as substrates. Prior to deposition procedure, an ultrasonic cleaning of all samples using “Lotonaxe” degreasing bath was performed; then the water-alcohol mixture cleaning and drying with hot air was made. Deposition equipment scheme is shown on Fig.1. Base pressure of vacuum chamber is 1*10 -3 Pa. Substrates were fixed on two-fold rotating table and its’ surface was activated in argon atmosphere using ion-beam gun at 500 V bias potential and heated to a temperature of 350 ± 20 °C. a-C/Cu nanocomposite films were deposited by high power DC magnetron sputtering process using high-performance industrial unit VU-SMA 600/4 [6]. Substrate-target distance of 100 mm and argon pressure 0.4 Pa were used during deposition. Cu/C mosaic type target with a 14 - 44 % carbon content supplied 7 - 20 at. % of carbon in the coatings. –100 V bias voltage was provided for deposition experiment. Power density on Cu/C 70 mm dia. targets (see Fig. 2.) reached 50 W/cm2, which ensured a deposition rate up to 0.10 µm/min. † Author for contacts: Mg.Sc.Ing Armands Leitans E-mail: armands.leitans@rtu.lv