Papers

ICMCTF2007 Session B6-2: Hard and Multifunctional Nano-Structured Coatings

Thursday, April 26, 2007 1:30 PM in Room Pacific

Thursday Afternoon

Start	Invited?	Item
1:30 PM		B6-2-1 Thermal Stability of TiAlN Based Nanoscale Multilayered Coatings J.K. Park, Y.J. Baik (Korea Institute of Science and Technology, Korea) In multicomponent metal nitride coating system, nanoscale multilayer structure has been studied to improve mechanical properties such as hardness and wear resistance. In high temperture application of nanoscale multilayer coating, however, thermal stability is critical because of thermodynamic instability of the sharp interface between nanoscale layers. The sharp interface is changed to diffused interface due to interdiffusion occurred at high temperature, then its mechanical properties can be deteriorated. In this presentation, we show the thermal stability of TiAlN based nanoscale multilayer coating. As a model system, amorphous Si-N and BN phase was selected as counter layer materials to the TiAlN layers, because Si-N and BN was reported to be stable matrix phase or continuous grain boundary layers in TiN based nanocomposite. We have prepared nanocsale multilayer coating by reactive magnetron sputtering. The multilayer coatings were annealed at various temperature from 600°C to 900°C. The thermal stability of nanoscale multilayer structure was analyzed by low angle X-ray reflectivity and TEM as a function of the change in compositional sharpness at interface between nanoscale layers with annealing. The hardness change with the microstructure was also observed. For comparison, crystalline CrN was chosen as counter layer material to the TiAlN layer and its thermal stability was also investigated. Contrary to the TiAlN/CrN nanoscale multilayer coating which showed deteriorated hardness with annealing, the hardness of TiAlN/Si-N (BN) nanoscale multilayer coating was improved with heat-treatment. The change in mechanical properties with annealing in TiAlN based nanoscale multilayer coating will be discuused in terms of interface structure and composition between TiAlN and counter layer materials (CrN, Si-N and BN).
2:10 PM		B6-2-4 Tribological Study of Nanocomposite PVD Coatings J.A. Garcia (Asociacion de la Industria Navarra (AIN), Spain); I. Azkona (METAL ESTALKI, S. L., Spain); M.J. Diaz, R. Martinez, R.J. Rodriguez (Asociacion de la Industria Navarra (AIN), Spain) New trends in metal industry require more advanced processes in terms of machining speed and low lubricant conditions. At this stage, conventional PVD coatings can not offer the required performance and it is needed to use new coatings with better properties in terms of hardness, elastic properties and wear resistance. In this scenario, nanocomposite structures are been proposed as a solution for advanced coatings This paper reports the tribological performance of different nanocomposite films coated by using a rotary arc technology. nc-TiAlN /Si₃ N₄, nc-TiN /Si₃N₄, nc-CrAlN /Si₃N₄, and CrAlN coatings were deposited on WC Co-cemented and high speed steel flat substrates, by employing an industrial PVD coating equipment. Composition, microstructure and thickness were characterised by using GDOES spectrometry and a field emission scanning electron miscroscope. Wear resistance and friction coefficient tests were carried out with a ball-on-disk tribometer and measured with an interferometric profilometer. The adhesion tests were done in a micro-scratch apparatus and the hardness of these coatings was measured with a Fischeroscope. The laboratory results obtained for the different coatings were compared with the performance of these coatings running in some selected industrial applications in conventional WC-Co and high speed steels tools.
2:30 PM		B6-2-5 Effect of Copper Addition on the Temperature Dependent Reciprocating Wear Behaviour of CrN Coatings M. Urgen, V. Ezirmik, K. Kazmanli, E. Senel (Istanbul Technical University, Turkey); A. Erdemir (Argonne National Laboratory) CrN-Cu nano-composite coating was produced by hybrid method using both cathodic arc and magnetron sputtering PVD technique. Reciproacting wear behaviour of the coating was investigated at room temperature, 50, 100 and 150°C. The tribological behavior is compared with undoped versions of CrN. The differences observed in the wear behavior is related to the character of the wear debris formed at the tribo-contact region which are characterized with micro-raman spectroscopy.
2:50 PM		B6-2-6 Anti-Wear and Anti-Bacteria Behaviors of TaN-Cu Nanocomposite Thin Films With and Without Annealing J.H. Hsieh, M.K. Cheng, Y.G. Chang, S.H. Chen (Mingchi University of Technology, Taiwan) TaNa-Cu nanocomposite films were deposited by reactive co-sputtering on Si and tool steel substrates. The films were then annealed using RTA (Rapid Thermal Annealing) at 400°C for 2, 4, 8 minutes respectively to cause the nucleation and growth of Cu particles in the TaN matrix and on the film surface. C-AFM, SSPM and SEM were applied to characterize the Cu nano-particles emerged on the surface of TaN-Cu thin films. Anti-wear and anti-bacterial properties were carried out to study the effect of annealing on these properties. The results reveal that annealing by RTA can cause Cu nano-particles to emerge on the TaN surface. Consequently, hardness and friction coefficients will change. The anti-bacterial behavior will also be affected.
3:10 PM		B6-2-8 Adjusted Thin Layers for the Electromagnetic Sheet Metal Forming Die W. Tillmann, E. Vogli, S. Mohapatra (University of Dortmund, Germany) Electromagnetic forming (EMF) is a high dynamic process using pulsed magnetic fields to form metals with high electrical conductivity such as aluminium. Due to the high forming velocities within the EMF-process with more than 300 m/s a high contact force between the workpiece and the die occurs during impact. To enhance the resistance of the die against wear and impact as well as to extend the lifetime of die, an innovative concept concerning the die surface modification has been developed. Among the wide variety of surface modification PVD is one of the most promising processes. In order to investigate the influence of the coated layers concerning the wear resistance of the die as well as the aluminium workpiece to be formed, different PVD layer systems have been developed, in which the hardness and toughness of the layers have been designed related to the soft aluminium sheets and high forming velocity. Corresponding metallographic, mechanical and microscopic investigations of the coated layers help to understand the relation between layer microstructure and tribological properties. Accompanying forming processes are employed to establish the correlations between developed layers and real forming conditions.
3:30 PM		B6-2-9 Nanostructured SiC by Chemical Vapor Deposition and Nanoparticle Impaction A. Beaber, L. Qi, J. Hafiz, W.W. Gerberich, S.L. Girshick, P.H. McMurry, J.V.R. Heberlein (University of Minnesota) SiC nanostructured coatings were deposited using a novel synthesis process combining chemical vapor deposition (CVD) with nanoparticle impaction (NPI). Indentation moduli (~370 GPa) and hardnesses (~39 GPa) approached the best commercially grown CVD films. Furthermore, film fracture toughness (~6 MPa*m^1/2) showed significant improvement to reported values in the literature. The nanoparticles were synthesized by injecting chemical reactants into a thermal plasma that undergoes a rapid expansion through a converging nozzle, resulting in gas-phase nucleation. This purposefully runs counter to design criteria for CVD, where the reactant concentration is kept low to avoid gas phase nucleation and a disordering of film growth. By limiting the residence time, the average particle size can be kept under 20 nm. However, these nanoparticle films suffer greatly from porosity. In the present paper, an increase in substrate temperature is used to enhance the amount of growth due to chemical vapor deposition. Particle formation was confirmed with in-situ particle size distribution measurements. The relative amount of chemical vapor to particle contributions to the film growth was investigated through observation of preferred growth orientation and microstructural characteristics. In addition, improvements in hardness and fracture toughness are presented and explained in terms of observed structural changes.
3:50 PM		B6-2-10 Effects of Superperiod, Interdiffusion, Orientation, and Phase/Polymorph Distribution on the Mechanical Properties of Nanostructured TiN/TaN Superlattices N. Patel (Carnegie Mellon University); A. Inspektor (Kennametal Inc.); P. Salvador (Carnegie Mellon University) Nanotechnology and the ability to tailor or design new properties by mixing materials on a nanoscale are changing the way new coatings and tools are developed. In this paper, we will present new results in nitride coatings built from crystallographically dissimilar materials, focusing on the synthesis and properties of nanostructured TaN/TiN superhard coatings. Monolithic TaN and TiN films, and the corresponding epitaxial TaN/TiN superlattices, were deposited on MgO (100) and on Al₂O₃ (0001) substrates by pulsed laser deposition in a N₂ atmosphere. Detailed XRD analyses show that the monolithic TaN films adopted either a cubic or hexagonal structure, depending on the processing conditions and the nature and orientation of the substrates. A comparison of growth, structures, and properties of the monolithic films and of the TaN/TiN superlattices will be discussed, with an emphasis on how the microhardness is affected by the superperiod and the film orientation.
4:10 PM		B6-2-7 Structural and Mechanical Properties of Nanocrystalline TiN Passivation Layer on TiNi Shape Memory Thin Films A. Kumar, R. Chandra, D. Kaur (IIT Roorkee, India) In oder to improve the surface properties and biocompatibility of TiNi based shape memory thin films, hard and adherent TiN protective layer coating by dc magnetron sputtering was examined. Magnetron sputtering with two separate Ti and Ni targets had been used to fabricate these films . Film stoichiometry was precisely controlled with the power to each target. The most important growth parameters influencing the grain size of TiN protective layer were found to be substrate temperature , ion bombardment rate and energy and nature of the sputtering gas (pure nitrogen and Argon- nitrogen gas mixture). The texture of the TiN films was observed to changes from 111 to 200 with change in nature of sputtering gas. Thickness and Size induced effects of TiN layer on surface and phase transformation properties of underneath TiNi layer were investigated. XRD, Insitu hot stage atomic force microscopy, DSC and nanoindentation studies were performed on both uncoated and TiN coated TiNi films and the results were compared. It was found that the presence of hard and adherent TiN layer on TiNi based shape memory thin films improves the hardness and surface properties while retaining shape memory effect.