Papers

ICMCTF2003 Session E5/G4-1: Smart Coatings for Green Manufacturing Tools and Surface Engineered Components

Monday, April 28, 2003 10:30 AM in Room California

Monday Morning

Start	Invited?	Item
10:30 AM		E5/G4-1-1 Self-Lubrication of Nitride Ceramic Coating by the Chlorine Ion Implantation T. Aizawa, T. Akhadejdamrong, A. Mitsuo (University of Tokyo, Japan) Titanium nitride has been widely used as a typical protective coating of cutting/drilling tools or forming dies. Although it have various features preferable for ceramic coating, two fatal demerits are pointed out, as compared to the carbide coating or diamond-like carbon (DLC). The first demit lies in the weakness against oxidation at the elevated temperature. Various modifications have been proposed to improve the oxidation toughness: e.g., (Ti, Al)N coating is a typical method for promising improvement of original TiN coating. Low wear toughness with high friction coefficient becomes the second demerit inherent to TiN: e.g., its friction coefficient (µm) ranges 1.0 to 1.4 while m is around 0.1 to 0.2 for DLC. In the present paper, the latter weak-point can be overcome by the chlorine implantation into TiN coating. Owing to the chlorine implantation to TiN with the dose of 1. 0 x 10¹⁷ ions/cm₂, its wearing mode against the stainless steel ball of AISI-304, changed from adhesive mode to abrasive mode, resulting in the reduction of wear volume and friction coefficient from 10^-5 and 1.0 - 1.4 to 10^-7 and 0.1 - 0.2, respectively. This drastic improvement of wear toughness comes from the self-lubrication mechanism, where the in-situ formed Magneli phase oxide of TiO_2-x on the wear track, works as a lubricious solid layer to significantly reduce the wear volume and friction coefficient. This self-lubrication mechanism is precisely described with aid of micro-focused XPS and HVTEM.
11:10 AM		E5/G4-1-3 Adhesion and Wear of Diamonds in Dry Contact K. Miyoshi (NASA Glenn Research Center) When a diamond is brought into contact with a metal, ceramic, or itself, strong bond forces can develop between the materials. The bonding forces will depend upon the state of the surfaces, cleanliness, and physical properties of the two materials, both surface and bulk. Also, the environment to which a diamond is exposed can markedly affect the bonding forces. Adhesion between a diamond and itself, or another material are discussed from a theoretical consideration of the nature of the surfaces and experimentally by relating bond forces to the interface resulting from dry, solid-state contact. Fracture and wear behavior of diamonds in dry contact are discussed as they relate to adhesion and friction. The dry lubricating abilities and wear-resistance of diamonds, such as natural, high-pressure synthetic, chemical-vapor-deposited (CVD), and diamondlike carbon (DLC), were examined by characterizing the adhesion, coefficients of friction, dimensional wear coefficients, and other surface characteristics. Various analytical techniques - including Raman spectroscopy, elastic recoil spectroscopy, Rutherford backscattering, transmission and scanning electron microscopy, x-ray photoelectron and Auger electron spectroscopy, x-ray diffraction, surface profilometry, and atomic force microscopy - were utilized to characterize the diamonds.
11:30 AM		E5/G4-1-4 A Study of the Transfer Behavior of Al 319 Alloy to Different Coatings During the Early Stages of Dry Sliding E. Konca, A.T. Alpas (University of Windsor, Canada) One of the main problems in dry machining of Al-Si alloys is the adhesion of aluminum to the tool surface limiting the number of holes that can be drilled. Coating of the drilling tools seems to be a possible solution to retard this sticking phenomenon. A coating will extend tool life if it decreases the adhesion tendency of aluminum and quickly dissipates the heat generated in the contact area. A pin on disc machine has been used to study the adhesion tendency of Al 319 alloy to different coatings. TiB₂ , TiN, TiCN, TiAlN, CrN, coated and uncoated M2 steel discs were tested against T5 heat treated Al 319 pins. Sliding distances were kept short to study the initial transfer behavior. The effects of sliding speed, sliding distance, temperature and working atmosphere were studied. Morphologies of sliding tracks were examined under Scanning Electron Microscope (SEM). With the aid of image analysis software these SEM images were used to rank the coatings according to the amount of aluminum they picked up and the debris generated during the tests. Results showed that transfer behavior depends on the properties of coating composition, test atmosphere and loading conditions. For most of the test conditions TiB₂ and TiCN picked much less aluminum compared to other coatings. TiB₂ coatings with relatively high surface roughness exhibited an interesting behavior: The amount of aluminum adhered increased until a certain sliding distance (about 70 revolutions), followed by a decrease approaching the value for the relatively smooth TiB₂ coating. In this paper the experimental results and the details of material transfer mechanisms will be discussed.
11:50 AM		E5/G4-1-5 Tribological Characteristics of MoS₂/WS₂ Solid Lubricating Multilayer Films S. Miyake, J. Noshiro, S. Watanabe (Nippon Institute of Technology, Japan) In order to obtain a low friction coefficient under dry sliding conditions, self-lubricating films and surface treatment have been widely developed. Especially, sputter-deposited MoS2 film has been often used as a dry lubricant in various industrial fields, such as space applications. Most investigations have been focused on the reduction of the friction coefficient. However, mechanical components require not only stable lubricating films for friction reduction, but also excellent wear resistance for prolonged endurance life. Therefore, in this work, anti-wear property of MoS₂/WS₂ nanometer-scale multilayer has been investigated, because a nanometer-scale multilayer film, so-called superlattice structured film, is expected to show a good mechanical properties, such as high hardness and high stiffness, resulting in showing a low friction and then long endurance lives. MoS₂/WS₂ nanometer-scale multilayer films, with individual layer thicknesses of 5, 10 and 20 nm, have been prepared by multi-target RF sputtering. Single-layer MoS₂ and WS₂ films were also prepared for comparison. Total thickness of each film was fixed at 500 nm. Ball-on-disk wear test and nono-indentation test were performed on the films grown onto Si substrates. MoS₂/WS₂ multilayer film (layer thickness: 10 nm) showed significantly improved tribological performance in air compared to the single-layer MoS₂ or WS₂ films, with an improvement in wear life of about 7 times, as keeping a low friction coefficient of about 0.05. This multilayer film shows potential for improved endurance with respect to current MoS₂-based low friction films and may be suitable for use in more severe friction conditions.