ICMCTF2006 Session B8-2: Hard and Multifunctional Nano-Structured Coatings

Thursday, May 4, 2006 1:30 PM in Room Golden West

Thursday Afternoon

Start	Invited?	Item
1:30 PM	Invited	B8-2-1 Multifunctional Biocompatible Nanostructured Coatings for Load-Bearing Implants D.V. Shtansky (Scientific-Educational Center of SHS, Russia); N.A. Gloushankova (Cancer Research Center of RAMS, Russia); I.A. Bashkova (Moscow State Institute of Steel and Alloys, Russia); M.A. Kharitonova, T.G. Moizhess (Cancer Research Center of RAMS, Russia); A.N. Sheveiko, P.V. Kiryukhantsev-Korneev (Moscow State Institute of Steel and Alloys, Russia); I.V. Reshetov (P.A. Hertsen Moscow Research Oncological Institute, Russia); E.A. Levashov (Moscow State Institute of Steel and Alloys (Technological University), Russia) To take advantages of the self-propagating high-temperature synthesis (SHS) technique, magnetron sputtering (MS), and ion implantation assisted magnetron sputtering (IIAMS), a new type of biocompatible nanostructured films were developed and studied. Films of Ti-Ca-C-O-(N), Ti-Ca-P-C-O-(N), Ti-Si-Zr-O-(N), and Ti-Zr-C-O-(N) were deposited by DC MS or IIAMS of SHS composite targets TiC_0.5+CaO, TiC_0.5+(CaO+TiO₂), TiC_0.5+(Ca10(PO₄)₆(OH)₂), Ti₅Si₃+ZrO₂, and TiC_0.5+ZrO₂ in an Ar atmosphere or reactively in a gaseous mixture of Ar+14%N2. The films were characterized in terms of their structure, chemical, mechanical, and tribological properties. The biocompatibility of the films was evaluated by both in vitro and in vivo experiments. In vitro studies involved the investigation of adhesion, spreading and proliferation of Rat-1 fibroblasts, MC3T3-E1 osteoblasts, and IAR-2 epithelial cells, morphometric analysis, actin cytoskeleton and focal contacts staining of the cells cultivated on the films. Alkaline phosphatase activity and von Kossa staining of osteoblastic culture were investigated. In vivo studies were fulfilled by subcutaneous implantation of Teflon plates coated with the tested films in mice and analysis of the population of cells on the surfaces. Implantation studies of Ti rings coated with Ti-Ca-P-C-O-N films using bone defect model in rats were also fulfilled. The results obtained show that Ti-based multicomponent nanostructured films possess a combination of high hardness and adhesion strength, reduced Young's modulus, low wear and friction, high corrosion resistance with bioactivity, biocompatibility and non-toxicity that makes films promising candidates as tribological coatings to be used for various medical applications like orthopedic prostheses, materials for connective surgery and dental implants.
2:10 PM		B8-2-3 Improvement of the Tribological Behaviour of PVD Nanostratified TiN/CrN Coatings, an Explanation C. Mendibide (Laboratoire des technologies Industrielles, Luxembourg); P. Steyer (INSA de Lyon-LPCI, France); J. Fontaine (Ecole Centrale de Lyon, France); Ph. Goudeau (Universitat de Poitiers, France) A hard TiN/CrN multilayered coating, consisting of alternating nanometer scale TiN and CrN layers (bilayer period of 40 nm), was deposited by arc evaporation process on M2 tool steel. Monolayered TiN and CrN are also deposited and used as references. The dry-sliding wear resistance was evaluated with a ball-on-disk tribometer, while surface fatigue resistance was determined by a cyclic multi-impact test. The architecture of layers is measured by XRD and observed by TEM. The residual stress field was characterized using XRD and the sin2 PSI method. All coatings present a columnar microstructure. Whatever the test, TiN presents a better wear resistance than CrN and this characteristic is still strongly increased by using the nanostratified coating. The differences in mechanical properties do not lead to a direct correlation with the tribological results, and therefore cannot explain such differences. Moreover, a microscopic analysis of the samples after both tribological tests reveals two opposite cracking mechanisms. TiN and CrN are subjected to a transversal crack propagation along the columnar grain boundaries until the peeling of the coating, whereas the multilayered coating only undergoes cohesive cracks deviated at each TiN/CrN interface. In our interpretation, the uniform compressive stresses developed in monolayered coatings lead to an orthogonal propagation of cracks until reaching the subjacent substrate. On the contrary, owing to the weak difference in lattice parameters of TiN and CrN, their nanostratification by epitaxy generates a cyclic fluctuated stress field localized in the interface zone. According to this model, validated by microscopic observations as well as by stress measurements, cracks propagate preferentially parallel to the interfaces in the TiN layers, and transversally in the CrN ones. Therefore each interface plays the role of obstacle to the progression of cracks, which significantly increases the lifetime of the coated part.
2:30 PM		B8-2-4 Grain Boundary Sliding Mechanisms in ZrN-Ag, ZrN-Au, and ZrN-Pd Nanocomposite Films S.M. Aouadi, P. Basnyat, Y. Zhang, Q. Ge, P. Filip (Southern Illinois University) Nanocomposite films of ZrN-Me (Me = Ag, Au, or Pd) were produced by reactive unbalanced magnetron sputtering and their structural, chemical, and mechanical properties were studied as a function of film composition. The films formed a dense and homogeneous microstructure whereby nanocrystals of Me are distributed evenly throughout the ZrN matrix. Interestingly, the Young's modulus was found to decrease much more dramatically with the increase in metal content for the ZrN-Ag system. A systematic ab initio study was undertaken to understand the mechanism of grain boundary sliding in these nanostructures and to correlate this phenomenon to the measured mechanical properties. Sliding was simulated quasistatically by shifting one grain with respect to the other by a small amount and then relaxing the structure. The maximum energy variation during the sliding was found to be the largest and the smallest for ZrN-Pd and ZrN-Ag, respectively.
2:50 PM		B8-2-5 Thermal Stability, Oxidation and Wear Resistance of Cr-Cu Based PVD Metallic Coatings K. Kanakis, O. Jimenez (The University of Sheffield, United Kingdom); M.A. Baker, M.A. Monclus (University of Surrey, United Kingdom); A. Leyland, A. Matthews (The University of Sheffield, United Kingdom) Cr-Cu based PVD metallic nanocomposite and/or amorphous coatings offer excellent mechanical and tribological properties. Such metallic films are characterised by moderately low elastic modulus and high hardness (for a metallic film), with increased engineering toughness and resilience. In contrast with brittle, high-modulus ceramic coatings, metallic films are more suitable for use on a range of low-alloy steel, stainless steel, copper alloy and/or light alloy substrate materials, whose wear resistance is otherwise poor. In this paper we discuss novel Cr-Cu based coatings, which contain additions of other elements such as Ti, N and B, in terms of thermal stability, oxidation and wear resistance. There is evidence that such coatings can be stable up to 600°C, with no decrease in hardness (which might be expected due to grain growth and/or relaxation of coating compressive stress). In some cases a significant increase in hardness is observed. Protection of low-alloy steels, stainless steels and copper alloys against oxidation resistance can also potentially be provided by such coatings, even with relatively low Cr contents of around 25at.%. Several techniques are employed for coating characterisation, such as X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Hardness, sliding wear and impact resistance have been evaluated for both as-deposited and annealed films by means of nanoindentation, reciprocating sliding and ball-on-plate impact testing, respectively.
3:30 PM		B8-2-7 Multilayered Adaptive Nanocomposite Coatings Exhibiting Low Friction Throughout a Broad Temperature Range C. Muratore, J.J. Hu, A. Korenyi-Both, A.A. Voevodin (Air Force Research Laboratory) Adaptive "chameleon" nanocomposite coatings provide low friction in broad ranges of environmental conditions through the self-induced formation of lubricious surfaces resulting from interactions with the ambient atmosphere. For example, nanocomposite yttria-stabilized zirconia (YSZ) coatings containing Ag, Mo and other nanosize inclusions depend on temperature-activated adaptations to yield low friction (< 0.2) from 25-700 C. Lubrication below 500 C results from diffusion and coalescence of silver at the surface, while MoO₃ and other compounds that shear easily at higher temperatures form by tribo-chemical reactions in the wear track above 500°C. The irreversible changes in composition and structure throughout the thickness of such coatings limits the utility of surface adaptation in applications where thermal cycling is expected. Moreover, some lubrication mechanisms occur over the entire coating surface in addition to the area experiencing wear, resulting in undesirable surface morphology and lubricant waste. To increase the wear lifetime and move toward thermal cycling capabilities of solid adaptive lubricants, different multilayer coating architectures incorporating nanocomposite YSZ-Ag-Mo isolated by TiN diffusion barrier layers were produced. Focused ion beam-generated cross sections of the coatings after heating show that the multilayered architecture guides solid lubricant and limits surface reactions to the worn area, resulting in coating lifetimes over ten times those of monolithic adaptive coatings of the same thickness. Additionally, layers of adaptive coating protected from the ambient atmosphere by the diffusion barrier layers maintain as-deposited homogeneity throughout extended periods of time at high temperature to provide low friction through multiple thermal cycles.
3:50 PM		B8-2-8 Investigation of Processing Parameters for Pulsed Closed-Field Unbalanced Magnetron Co-Sputtered Titanium Carbide Thin Films J.M. Anton, B. Mishra, J.J Moore (Colorado School of Mines); J.A. Rees (Hiden Analytical Ltd.); W.D. Sproul (Reactive Sputtering Consulting, LLC) Titanium carbide is a well-established wear resistant coating due to its excellent tribological properties including high hardness and elastic modulus, good wear resistance, low coefficient of friction against steel, and high temperature stability. Recent advances in sputtering technology have resulted in improvements in the properties and performance of wear resistant coatings. Closed-field unbalanced magnetron sputtering and pulsed magnetron sputtering have greatly improved the structure and properties of titanium carbide films by increasing ion bombardment at the substrate. The goal of this research was to investigate how processing ties into the structure-property-performance relationship for these types of films. An electrostatic quadrupole plasma analyzer was used to measure the energy of ions at the substrate position. Energy ranges from 0.5 to 280 eV were observed under different pulsing conditions. Excessively high ion energy during deposition was found to erode the tribological performance of films.
4:10 PM		B8-2-9 Deposition and Characterization of Hybrid Filtered Arc-Magnetron Multilayer Nanocomposite Cermet Coatings for Advanced Tribological Applications V.I. Gorokhovsky, C. Bowman (Arcomac Surface Engineering, LLC); P.E. Gannon (Montana State University-Bozeman); D. VanVorous (Arcomac Surface Engineering, LLC); J.J. Hu, C. Muratore, A.A. Voevodin (Air Force Research Laboratory); V. Wedeven (Wedeven and Associates) The demand for low-friction, wear and corrosion resistant components, which operate under severe conditions has directed attention to advanced surface engineering technologies. The Large area Filtered Arc Deposition (LAFAD) process has demonstrated atomically smooth coatings at high deposition rates over large surface areas¹. In addition to the inherent advantages of conventional filtered arc technology (superhardness, improved adhesion, low defect density), the LAFAD technology allows functionally graded, multilayer, and nanocomposite architectures of multi-elemental coatings via electro-magnetic mixing of two plasma flows composed of different metal vapor ion composition. Further advancement is realized through a combinatorial process using a hybrid filtered arc-magnetron to deposit multilayer nanocomposite TiCrN+TiBC cermet coatings. Multiple coating architectures were reviewed and designed to provide optimized protection for corrosion, wear and fatigue resistance of Pyrowear 675 and M50 steels used in aerospace bearing and gear applications. Coating properties were characterized by a variety of methods including SEM/EDS, HRTEM, XRD, AFM, nanoindentation, and residual stress calculation by contact profilometry. Wear and corrosion testing results were obtained for atmospheric corrosion, reciprocating/fretting sliding, high stress boundary lubricated sliding, high temperature rolling contact fatigue, and advanced simulation testing for scuffing performance under oil starved operating conditions. ¹Vladimir I. Gorokhovsky , Rabi Bhattacharya and Deepak G. Bhat, Surface and Coating Technology, 140 (2) 2001, pp. 82-92.
4:30 PM		B8-2-10 Nanocomposite nc-MeC/a-C Thin Films for Electrical Contact Applications E. Lewin, O. Wilhelmsson, U. Jansson (Uppsala University, Sweden) Nanocomposite thin films consisting of nanocrystalline metal carbide (nc-MeC) and an amorphous carbon (a-C) matrix have been deposited using non-reactive magnetron sputtering. We have investigated several systems including Nb-C, Zr-C, V-C and Ti-C, where the Ti-C system has received most of our attention. Total film composition and deposition temperature was varied from 46 to 88 at.%, and from room temperature to 400°C, respectively. The films were analysed with regard to phase composition and microstructure (using XRD, XPS, Raman, TEM and SEM), and the results have been correlated to electrical properties (resistivity and contact resistance). Mechanically the nanocomposite films exhibit hardness, elasticity and friction values that are expected of this type of material. Through design of the microstructure an appropriate combination of electrical and mechanical properties may be attained. Deposited films show promising results for applications as coatings on electrical contacts, combining low friction, mechanical stability and low contact resistance.