Mechanical Properties and Adhesion

Friday, May 4, 2001 8:30 AM in Room San Diego

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8:30 AM F1/E4-3-1 Micro/Nanomechanical and Tribological Studies of Bulk and Thin-Film Materials Used in Magnetic Recording Heads
X Li, B Bhushan (The Ohio State University)
The head body of thin-film magnetic read-write heads used for tape and rigid disk drives is made of magnetic ferrites or nonmagnetic Al@sub 2@O@sub 3@-TiC and the head construction includes coatings of magnetic alloys, insulating oxides and bonding adhesives. Wear of head structure results in recession of head structure with respect to the air bearing surface of the head body, known as pole tip recession. It is essential that the materials used in magnetic recording heads have good micro/nanomechanical and tribological properties. Micro/nanomechanical characterization of Ni-Zn ferrite, Al@sub 2@O@sub 3@-TiC, and thin films of Al@sub 2@O@sub 3@, CoZrTa, and NiFe have been carried out. Hardness, elastic modulus and scratch resistance of these materials were measured by nanoindentation and microscratching using a nanoindenter. Fracture toughness was measured by microindentation using a microindenter. Friction and wear properties were measured using an accelerated ball-on-flat tribometer. These data along with a discussion on failure mechanisms of these materials during scratch and wear are the subject of this paper.
8:50 AM F1/E4-3-2 Characterization of N-doped Cr Coating and Nanoscaled Cr/DLC Multilayers on Intensified Plasma Nitrided 4340 Steel
X. Nie, J.C. Jiang, V. Singh (Louisiana State University); E.I. Meletis (Lousiana State University)
Electroplating of Cr is an issue of increasingly environmental concern. Duplex intensified plasma nitriding/coating treatments have the potential to overcome this problem. The intensified plasma-assisted process (IPAP) can be used for both nitriding and coating deposition in the same system at a relatively low temperature. The substrate material in the present study was 4340 steel. It was first treated by IPAP plasma nitriding and then N-doped Cr coatings were deposited using Cr magnetron sputtering in N@2@ + Ar mixture. Comparative studies were conducted with sputtered Cr and electroplated Cr coatings in terms of hardness, wear and corrosion resistance. In an effort to improve the tribological behavior of Cr coatings, nanoscaled N-doped Cr/DLC mutlilayers were also deposited using magnetron sputtering in combination with low pressure CVD of DLC coating at Ar + CH@4@ + N@2@ atmosphere. The Cr sputter target was shadowed by a shutter, of which the on and off time can be adjusted, producing various Cr/DLC layer thickness ratios. Surface topography was characterized by scanning probe microscopy. High resolution transmission electron microscopy of cross sections was employed to study the ion plated Cr coatings and the nanoscaled structure of the multilayers. Hardness, adhesion and wear properties were assessed by conducting nanoindentation, pull testing and pin-on-disc experiments. The relationship between coating behavior and structure is discussed.
9:10 AM F1/E4-3-3 Evaluation of Thin C- and Diamond Coatings by Impact Testing
O. Knotek, E. Lugscheider (University of Technology (RWTH) Aachen, Germany); T. Leyendecker, G. Erkens (CemeCon GmbH, Germany); K.-D. Bouzakis ( Aristoteles University of Thessaloniki, Greece)
The impact testing of hard coatings combined with other methods can be done by adopting the test procedures to the reaction carbide ball – C-containing coating surface. The fatigue behaviour of the interface coating – carbide substrate will be described sufficiently even at short testing time. The results can be correlated to the suitability of these films during application. The development of special cutting tools coated by diamondlike coatings is supported by this testing method.
9:30 AM F1/E4-3-4 Mechanical Properties of Ti-B-C-N Coatings Deposited by Magnetron Sputtering
D. Zhong, E. Sutter, J.J. Moore, G.G.W Mustoe (Colorado School of Mines); J. Disam, S. Thiel (Schott Glas, Germany); E.A. Levashov (Moscow Steel and Alloys Institute, Russia)
It is well known that, in general, multicomponent coating systems lead to a more favorable performance during application in most cases. Coatings in the Ti-B-C-N quaternary system are hard and abrasion resistant materials that have been also identified as potential erosion resistant materials. In the present work, Ti-B-C and Ti-B-C-N have been deposited from a TiB@sub 2@-TiC composite target by RF magnetron sputtering. In this paper, their mechanical properties, including nano-hardness, Young's modulus, film adhesion and residual stress are presented. The relationships among deposition process, film microstructure and these properties are discussed as well.
9:50 AM F1/E4-3-5 High Rate Deposition of TiAlN Wear and Tear Protective Coatings by Means of Vacuum Arc Evaporation
M. Holzherr, M. Falz, R. Wilberg (VTD Vakuumtechnik Dresden GmbH, Germany)
There has been a tremendous growth in significance of TiAlN coatings for wear and tear protection of tools, over the last few years. Because TiAlN coated tools can be employed at considerably higher temperatures than those with classic TiN coatings, TiAlN is often used for dry work, or for processes involving minimal amounts of lubricant. Using high rate coating by means of ARC evaporating in the small industrial plant DREVA @superARC@ 400, a TiAlN wear and tear protective film of 2µm thickness can be deposited within less than 10 minutes. Thus, the rate of deposition is about one scale higher than that for customary industrial standard coatings. Characterisation of the properties (hardness, adhesion) of coatings produced this way, as a function of the rate of deposition and other process defining parameters, such as bias voltage, gas flow, and target used, has been done and the results will be presented. The research was carried out with powder as well as melting metallurgically alloyed targets of varying Ti/Al compositions. Results of testing the drills will be presented and discussed.
10:10 AM F1/E4-3-6 Scratch Behavior and In-Situ Acoustic Emission Analysis of Electroless Ni-P Modified Chromium Nitride Coating
F.B. Wu, J.G. Duh (National Tsing Hua University, Taiwan)
The reactively sputtered chromium nitride (CrN) deposit on mild steel (MS) was initially modified with the electroless nickel (EN) interlayer. The composition of both the CrN and EN coatings were evaluated and homogeneity in microstructure was revealed. An alternative approach in determining the crystallinity of as-deposited EN plating on the basis of the X-Ray diffraction pattern was proposed and discussed. The scratch test was further conducted to evaluate the critical load, adhesive and cohesive properties of the coating assemblies. Intensive studies were focused on failure modes of the single and multi-layer coatings judged from scratch channels as well as the acoustic activity. Relationships between progressive, constant loading, and the in-situ acoustic emission signal during scratching were presented. In addition, effects of heat treatment and interlayer thickness on the scratch behavior of the single and multi-layer coating assemblies were also analyzed.
10:30 AM F1/E4-3-7 Investigation of the Fatigue Failure Progress of PVD Elastoplastic Coatings with Various Roughness During the Impact Testing
K.-D. Bouzakis, K. David, A. Siganos ( Aristoteles University of Thessaloniki, Greece); T. Leyendecker, G. Erkens (CemeCon GmbH, Germany)
The progressive implementation of thin hard coatings in various industrial applications, which involve severe dynamic stress states such as cutting and forming tools, bearings etc. requires the precise knowledge of the coating fatigue stress limits. Both these critical stresses and the coating failure mechanisms may be taken into account to ensure operating conditions within secure region considering the coating continuous endurance. The coating impact test was introduced in the past years as a convenient experimental method that has been proved able to determine quantitatively the fatigue behavior of coating-substrate compounds. In the present paper using a developed impact testing machine, supported by appropriate control, monitoring and evaluation facilities, the fatigue performance of thin hard coatings having various surface integrities is investigated. The examined coatings are monolayer PVD coatings, as well as coatings consisting of two distinct layers. The experimental procedure proved that there is an enormous shortening of the coating endurance when roughness deteriorates. This phenomenon was observed in all examined coatings. The failure mechanisms that characterise the coating fatigue performance were analysed by means of FEM simulation techniques taking into account the surface integrity and the coating elastoplastic behavior. Emphasis is paid on the analysis of the smooth PVD monolayer coating performance, for which Smith and Woehler fatigue diagrams have been established. The effect of the coating roughness on the coating fatigue strength is also quantitatively determined.
10:50 AM F1/E4-3-8 Study of Chemical Reactions and Thin Film Properties of RF Plasma Deposited C@sub 6@H@sub 6@ Films
M.A. Algatti, E.F. Lucena, C.P. Rita, N.C. Cruz, E.C. Rangel, R.P. Mota, R.Y. Honda, M.E. Kayama (Unesp - Universidade Estadual Paulista, Brazil)
This papers deals with the study of the chemical reactions in gas phase on RF excited plasmas in benzene atmospheres and mechanical properties characterization of resulted films. The study was carried out using actinometric optical emission espectroscopy and mass spectrometry. The optical spectra were obtained with a 2m focal distance plane-grating monocromator whose output was coupled to a photomultiplier operating in the wavelength range from 250 to 800nm. The mass spectra were obtained by a mass spectrometer Hiden Analytical model EQP300 with a resolution of 1amu, operating in the mass range from 1 to 300amu. The RF excited plasmas were generated within a stainless steel cylindrical reactor in a plane parallel plate configuration. The RF power supply operating in 13.56MHz was capacitively coupled to the chamber through an appropriate matching network. The study allowed one to follow the trends of the CH specie for different values of pressure and power. The results obtained showed that the presence of CH specie, for discharges generated at 50 mTorr with the RF power ranging from 10 to 40W, could be explained by the following chemical reaction: CH@sub 3@@super *@ + e@super -@---> CH + 2H + e@super -@, e.g., the CH resulting from the breaking of the C-H bound with the liberation of 2 H atoms. This assumption is quite reasonable if one consider that the electronic recombination occurs in a time scale shorter than the lifetime for most of the excited states of the CH@sub 3@ radical. The results also showed that for discharges generated at 40 W with the pressure ranging from 35 to 90mTorr the trends of CH could be explained through the chemical reaction CH@sub 3@@super *@ + e@super -@---> CH + H@sub 2@ + e@super -@. Further exposure of the benzene films to ion bombardment using plasma immersion implantation techniques with argon and nitrogen revealed an increase of 20% to 30% of film hardness which was measured through nanoindentation techniques.