TMMOB Metalurji ve Malzeme Mühendisleri Odas ı E ğ itim Merkezi Bildiriler Kitab ı 1207 19. Uluslararas ı Metalurji ve Malzeme Kongresi | IMMC 2018 Tribological Behavior of TiAlNi, AlTiN, AlCrN Coatings Under Dry and Lubricated Conditions Doğuş Özkan¹, Yaman Erarslan², Levent Kara³, M. Alper Yılmaz4, M. Barış Yağcı5, Egemen Sulukan¹ ¹National Defense University, Naval Academy, Department of Mechanical Engineering, Istanbul, Turkey ²Yıldız Technical University, Department of Metallurgical and Materials Engineering, Istanbul, Turkey ³Erzincan University, Department of Mechanical Engineering, Erzincan, Turkey 4National Defense University, Barbaros Naval Science and Engineering Institute, Istanbul, Turkey 5Koc University, Surface Science and Technology Center, Sarıyer, Istanbul Abstract In this study, ~3.5 m thick multilayer TiAlN, AlTiN, and AlCrN coatings were deposited on the H13 steel surface by Cathodic Arc Physical Vapor Deposition (CAPVD) method. The tribological performance of the coatings were evaluated by a tribometer at dry and boundary lubrication conditions. Then, coating surfaces were investigated by optical microscope, optical profilometer and atomic force microscope (AFM) to evaluate the morphological changes, wear volumes and tribofilm thickness. Also, Scanning electron microscopy (SEM/EDX) and X-ray photoelectron spectrometry (XPS) analysis were applied to coating surfaces for the tribochemical evolution of the tribofilm. Results showed that AlCrN coating performed the best tribological behavior at dry and lubricated conditions, when compared to TiAlN and AlTiN coatings. 1. Introduction Wear and friction of sliding surfaces are important phenomena in mechanical systems [1]. Higher friction addresses higher energy loss in mechanical systems. Wear, in addition, is an indicator of system effective life or system components life due to the material damage [2]. To decrease friction and wear in moving parts of an engine, lubricating oils are widely used. These lubricants form a protective tribofilm between sliding surfaces by decomposition of the additives such as zinc dialkyl dithiophosphate (ZDDP) present in their composition [3, 4]. However, tribofilm can fail to protect sliding surfaces at boundary lubrication condition. This failure causes metal-to-metal contact, resulting in higher wear rates for sliding surfaces. The cylinder liner-piston ring tribological system, cam tappets/followers, and bearings can operate at boundary lubrication condition in internal combustion engines due to inadequate lubrication. When moving parts of an engine work at boundary lubrication condition, it is essential to provide wear resistance for sliding surfaces to protect them from any material damage. One way to have wear resistant surface to prevent metal-to-metal contacts at boundary lubrication condition is surface treatment by coatings. Therefore, some moving parts of engines are coated with various surface coatings. For example, top piston rings are generally coated with chromium to get wear resistance surface. Similarly, crank bearings are coated with different composites such as aluminum alloy, and copper-lead-tin alloys. In this tribological behavior of hard TiAlN, AlTiN, and AlCrN coatings were investigated to evaluate the possibility of being a wear resistance coating for cam tappets of an engine at dry and boundary lubrication conditions. As a result, AlCrN among the all three coatings showed the best tribological performance at both conditions. 2. Materials and Methods 2.1. Coating deposition and characterization H13 steel samples were hardened by heat treatment through quenching and tempering at 600 °C. Following this, samples were mechanically polished to average surface roughness of 150 μm, and then ultrasonically cleaned for nitrating operation. 3.5 μm thick multilayer TiAlN, AlTiN and AlCrN coatings were deposited on steel substrates by Cathodic Arc Physical Vapor Deposition (CAPVD) coating method. Al67Ti33 and Al70Cr33 targets were used to deposit TiAlN, AlTiN and AlCrN coatings, respectively. Prior to deposition process, H13 tool steel samples were first heated to 450 C, then ion etched via Cr bombardment. During the coating process, temperature of the substrate was kept at about 450 °C due to the IR and plasma heating. The chamber was evacuated to about 10 -3 Pa vacuum pressure level. Nitrating process was carried under 100V bias voltage and 99.9 % Nitrogen purity at 1 Pa pressure. After the coating application, the cross- section of the samples were polished to evaluate the coating thickness under SEM. Elastic modulus and hardness of the coatings was measured by Nano indentation analysis with Agilent G200 Nano indenter.