ICMCTF2002 Session E5/D4-2: Properties and Applications of Diamond, Diamondlike and Related Coatings

Thursday, April 25, 2002 1:30 PM in Room California

Thursday Afternoon

Start	Invited?	Item
1:30 PM	Invited	E5/D4-2-1 Preparation, Microstructural Characterisation and Tribological Behaviour of CN_x Coatings A. Fernandez (Instituto de Ciencia de Materiales de Sevilla. CSIC, Spain) A review is presented on the main results obtained during the last years on the synthesis and microstructural characterisation of CN_x and Si doped CN_x coatings prepared mainly by the magnetron sputtering technique. An exhaustive characterisation by XPS, EELS, IR, XAS and NMR has allowed us to determine the microstructure of the films obtained under different experimental conditions and with different compositions. Thermal stability studies in vacuum and air atmosphere provided also a limit of practical use capabilities of the films. Finally the relationships between the nature of the films and the friction behaviour are highlighted and discussed.
2:10 PM		E5/D4-2-3 Frictional Behavior Of Diamondlike Carbon Films In Vacuum and Under Varying Water Vapor Pressure J. Andersson (Uppsala University, Sweden); R.A. Erck, A. Erdemir (Argonne National Laboratory) In this study, we investigated the friction behavior of hydrogen-free and highly hydrogenated diamondlike carbon (DLC) films in high vacuum (10-8 Torr). Further, in order to elucidate the effects of various gaseous species on tribological behavior of DLC films, we used introduced different gases into the vacuum chamber. The hydrogen-free DLC was produced in an arc-PVD and the highly hydrogenated DLC was produced using plasma enhanced chemical vapor deposition (PECVD). Tribological evaluation was conducted in a pin-on-disc setup with DLC-coated steel balls and DLC-coated steel discs in matched pairs under a 1 N load and with constant rotational frequency at speeds in the range of 0.025 to 0.075 m/s. In vacuum, the steady-state friction coefficient of the hydrogen-free film was of the order of 0.6 and the wear was severe, whereas for the highly hydrogenated film friction was below 0.01 and in an optical microscope no wear could be detected. Adding water vapor to the system had profound effects on the tribological behavior of both films. Micro-laser-Raman spectroscopy and electron microscopy were used to elucidate the structural chemistry of these films, and to interpret their friction and wear mechanisms, respectively.
2:30 PM		E5/D4-2-4 Superlow Friction of Diamond-like Carbon Films: a Relation to Viscoplastic Properties J. Fontaine, J.L. Loubet (Ecole Centrale de Lyon, France); C. Donnet (University J. Monnet., France); T. Le Mogne (Ecole Centrale de Lyon, France); A. Grill (IBM T.J. Watson Research Center) Composition, structure, properties and tribological behavior of diamond-like carbon films (DLC) strongly depend on the deposition technique and conditions. Plasma-enhanced chemical vapor deposition (PECVD) allows the deposition of amorphous hydrogenated carbon films (a-C:H) exhibiting superlow friction properties in ultra-high vacuum. We have shown previously, for different sets of films deposited in the same process chamber, that a minimum content of hydrogen was necessary to reach friction coefficients of 0.01 and lower against steel pin in ultra-high vacuum. However, the value of this critical hydrogen content varies over a wide range, between 30 at.% and 46 at.%, depending on process chamber. The present paper reports tribological experiments and mechanical properties of several DLC films obtained with different deposition conditions and process chambers. Friction coefficients were measured in an UHV analytical tribometer. The mechanical properties were evaluated from force-displacement curves using a nanoindentation instrument. Through an original control of the load during indentation, we performed measurements at constant strain rates. Besides Young's modulus and hardness, we were thus able to determine the importance of viscoplastic contribution for these films. The aim of this paper is to highlight the correlation between superlow friction and viscoplastic behavior.
2:50 PM		E5/D4-2-5 Effect of Surface Treatment on the Adhesion of DLC Film on 316L Stainless Steel M.M. Morshed, B.P. McNamara, D.C. Cameron, M.S.J. Hashmi (Dublin City University, Ireland) Diamond-like carbon (DLC) film has been deposited on to substrates of 316L stainless steel, a substrate material which is widely used for implant purposes, using a saddle field neutral beam deposition system with an acetylene/argon mixture of varying composition as the process gas. The substrates were etched in situ by neutral argon atom sputtering for different time durations prior to deposition. It has been shown that the adhesion measured by the perpendicular pull-off test is inversely proportional to the level of residual stress in the films as measured by the bending beam method. The degree of correlation between the pull-off and scratch tests for adhesion is discussed. The stress is also shown to be related with the sp³ content of the films. Results are presented of these relationships. The effect of the argon atom etching treatment on the adhesion of the film to the substrate is presented. .
3:10 PM		E5/D4-2-6 Properties of Boron Carbide/DLC Multilayer Films with Infrared Heating M.Y. Chen (Air Force Research Laboratory); J.H. Li, J.W. Seok, R.Y. Lin (University of Cincinnati) Stoichiometric boron carbide in bulk ceramic form has demonstrated extreme hardness and chemical inertness due to its covalent bonding. There is strong interest in boron carbide coatings for protective, wear, or corrosion resistance applications. In this work, a multilayer concept was used to improve the film properties of boron carbide materials and avoid their inherent brittleness. Monolithic and multilayers of boron carbide/DLC films were deposited using dc magnetron sputtering with and without a negative bias. Furthermore, films were subjected to infrared rapid anneal to investigate its effect on film properties. Analytical techniques including x-ray photoelectron spectroscopy and standard x-ray diffraction analysis were used to determine the composition, chemical bonding, and phase structure of the coatings. Mechanical evaluation were performed including nanoindentation, scratch testing, and pin-on-disc tribotesting. The effects of multilayer composition, bilayer thickness, negative substrate bias, and subsequent IR heating on film properties such as hardness, fracture toughness, and film adhesion to steel will be presented.
3:30 PM		E5/D4-2-7 Tribological Properties of High sp³/ High sp² DLC Multilayers P. Gupta, V. Singh, E.I. Meletis (Louisiana State University) DLC films are characterized as amorphous containing defected sp ³ and sp ² domains, with advantages and disadvantages associated with each one of these domains, in terms of properties. For example, high sp ³-content films possess high hardness but also high residual stresses limiting the film thickness. Multilayered DLC/DLC films consisting of alternate nano-layers with high sp ³ and high sp ² content provide great promise to alleviate drawbacks. The present study is focused on the synthesis, characterization and properties of DLC/DLC multilayered films. Multilayered DLC films were synthesized varying the thickness of the high sp ³ and high sp ² nanolayers and the sp ³ and sp ² content. The films were deposited on Si substrates in a plasma environment composed of CH ⁴ and Ar gas mixture. The effect of layer thickness variation on resulting film properties was investigated. Bonding characteristics in each layer were studied by FTIR. The surface morphology and film structure was characterized by SEM and cross-sectional high-resolution TEM, respectively. Film hardness was characterized by microhardness and nano-indentation measurements. Tribological properties were studied by conducting pin-on disk experiments. The behavior of DLC multilayered films is discussed in view of the present findings.
3:50 PM		E5/D4-2-8 Tribological and Structural Studies of Diamond-like-carbon and Fluorocarbon Thin Films J.G. Goldsmith, E.S. Sutter, J.M. Moore, B.M. Mishra (Colorado School of Mines); M.C. Crowder, R.T. Turner (Maxtor Corporation) Fluoropolymers are known for their chemical resistance and low friction properties. In the hard drive industry very thin layers of diamond-like-carbon (DLC) and fluorocarbon films are used to improve the tribological properties of magnetic disks. Improvement of the tribological properties is required as maximizing the storage capacity demands minimizing of the distance between the read-write head and disk interface. The low-friction DLC or fluorocarbon films are typically less than 20nm thick, and investigating their properties is a challenge. In the present work we have carried out deposition of fluorocarbon films using plasma deposition technique. The chemical composition of the deposited fluorocarbon films has been investigated using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The films structure was studied using atomic force microscopy and cross-sectional transmission electron microscopy. The chemical and structural properties of the fluorocarbon films as well as their wear, coefficient of friction, wettability with water, hardness, fracture toughness, index of refraction, dielectric constant, and resistivity were compared to DLC films with similar thickness. The relationship between deposition conditions, structure, and properties is discussed.
4:10 PM		E5/D4-2-9 Tribological Performance of Nanocomposite Coating Based on Diamond-like Carbon S. Zhang (Nanyang Technological University, Singapore); X.T. Zeng (Gintic Institute of Manufacturing Technology, Singapore); Y.Q. Fu (Nanyang Technological University, Singapore) Superhard nanocrystalline (Ti, Cr)/CNX coatings were prepared through co-sputtering of Ti, Cr and graphite targets. In the nanocomposite coating, DLC acted as hard, tough and lubricating matrix, while nano-particles of TiN, CrN, TiC and CrC particles were deposited as reinforcing crystallites imbedded in the amorphous matrix. The effects of the process parameters on the coating properties were studied. Atomic force microscopy(AFM), X-ray diffraction (XRD), nanoindenter and XPS were used to characterize the films. Tribological behaviors were evaluated using a ball-on-disk tribometer. The films demonstrated properties of low-friction and good wear resistance.
4:30 PM	Invited	E5/D4-2-10 How Diamond-like Carbon Coatings Achieve Low Friction and Low Wear in a Sliding Contact I.L. Singer, T.W. Scharf (US Naval Research Laboratory) Diamond-like carbon (DLC) coatings are hard, smooth and mainly amorphous. They can exhibit very good wear resistance and low friction coefficients (<0.01 to 0.1). But like the proverbial double-edged sword, they can either protect bearing surfaces or destroy them. We have tested commercial DLC coatings in a ball vs. flat geometry with a variety of ball materials and under high stress (0.5 - 1.5 GPa) sliding contact in air or N2 and in lubricants. Three conditions have been seen: 1) the ball wears, creating loose debris and unacceptable wear; 2) a transfer film forms on the ball, protecting the ball and minimizing wear of the coating; 3) virtually no wear or transfer film can be seen with either couple. All three situations have been seen in both dry and lubricated sliding contact. NRL's in situ optical/Raman tribometer has been used to investigate the run-in and steady state sliding behavior for all three conditions. Condition 2) has been studied most extensively, and will be the focus of this presentation. The studies have made clear that, while coating/substrate properties such as adhesion, smoothness and hardness are necessary for good tribological properties, the protective properties of the coatings are governed by more subtle processes taking place at the sliding interface. These processes, including tribochemistry, third body formation, transfer film dynamics and establishment of a single velocity accommodation plane, will be identified, and their role in obtaining low friction coefficients will be established.