ICMCTF2008 Session B6-3: Hard and Multifunctional Nano-Structured Coatings

Tuesday, April 29, 2008 8:00 AM in Room Golden West

Tuesday Morning

Start	Invited?	Item
8:00 AM	Invited	B6-3-1 Nanostructured Crystalline/Amorphous Composite Films for Multifunctional Hard-Coatings K.H. Kim (Pusan National University, Korea) The current topics in this paper are related to the multi-component coatings based on the nano-structured crystalline/amorphous composites, which have various hybrid-multifunctions. The syntheses on the basis of materials design and deposition techniques, and characterization of the coatings are introduced. For this study, a hybrid system of arc ion plating (AIP) and magnetron sputtering (MS) techniques were mainly used. Various kinds of ternary, quaternary and quinary nano-structured coatings in the (Ti, Cr, Mo, Al, Si)-(B, C, N) system were successfully synthesized on various substrates. The results obtained showed that nanocomposite coatings composed of nanocrystalline grains of nitride, carbide, or boride surrounded by amorphous matrix (SiNx, SiC, BN, etc) were good candidates for structural hard-coatings having hybrid-multifunction. Codepositions of the amorphous and nanocrystalline phases of various compositions were investigated. The maximum hardness ranging from 30 GPa to about 60 GPa has been observed for most nanocomposite coatings. Adding the elements of Mo, Al, Si, B, C into the previous TiN and CrN coatings can improve the hardness of the coatings either by solution strengthening or by grain size diminution effect, while addition of Cr, Al and Si can improve the thermal stability and oxidation resistance by formation of protective oxide layer on the surface, and addition of C, Si, Mo can decrease the friction coefficient. By adjusting the composition and deposition parameters of the coatings, superior multifunctional coatings can be obtained.
8:40 AM		B6-3-3 Structure and Properties of Ti-B-C-N Nanocomposite Coatings Prepared by Pulsed Closed Field Unbalanced Magnetron Sputtering (P-CFUBMS) J. Lin, B. Mishra, J.J. Moore (Colorado School of Mines); M. Pinkas (Nuclear Research Center, Israel); W.D. Sproul (Reactive Sputtering, Inc.) Ti-B-C-N nanocomposite coatings with various nitrogen contents were synthesized using a pulsed closed field unbalanced magnetron sputtering (P-CFUBMS) system. A TiB₂ -TiC compound target was sputtered using a pulsed power supply in Ar/N₂ plasma. The coatings were characterized using grazing incident X-ray diffraction (GIXRD), x-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), scanning transmission electron microscopy (TEM), nanoindentation, and microtribometry. The results indicate that Ti-B-C-N nanocomposite coatings consist of nanocrystalline (Ti,C)B₂ and (Ti,C)N dispersed in an amorphous matrix of BN. Microstructure and properties (hardness, elastic modulus, wear resistance) of the TiBCN coatings exhibited a dependency on the nitrogen concentration. Significant amorphous phase formation and grain refinement were observed when the nitrogen concentration in the coatings was greater than 13 at.%. It was found that TiBCN coatings with 5-13 at% nitrogen exhibit an optimum combination of high hardness (35-48 GPa), good wear resistance (1.0-1.2x10^-6mm³N^-1m^-1), and good fracture toughness (H/E>0.1). If the nitrogen content in the coatings exceeds 13 at%, the hardness, H/E values, and the wear resistance of the TiBCN coatings decrease rapidly.
9:00 AM		B6-3-4 Nanoparticles Disperse- Strengthened Coatings Produced by Chemical Reaction Assisted Pulse Electrospark Deposition (CRAPED) E.A. Levashov, V.V. Kurbatkina (State Technological University/Moscow Institute of Steel and Alloys, Russia); L.C. Lev (General Motors R&D and Planning); E.I. Zamulaeva, A.E. Kudryashov, P.V. Vakaev (State Technological University/Moscow Institute of Steel and Alloys, Russia); Yu.S. Pogozhev (Technological University/Moscow Institute of Steel and Alloys, Russia) Three groups of electrode materials for CRAPED were considered: dispersive-hardening ceramic materials with effect of simultaneous strengthening of carbide grains and metallic binder result in precipitations which appeared due to concentration separation of supersaturated solid solutions; nanoparticles disperse-strengthened composite materials based on titanium carbide and diboride with modified structure produced using focused alloying by refractory compounds nanoparticles which are modificators affected to the process of structure formation thought the liquid phase and lock the recrystallization; nanocomposite cemented carbide. Mechanisms of concentration separation of supersaturated solid solutions are discussed. The follow requirements to electrodes are proposed: high volume of grain boundaries; average grain size of refractory compound phases could be around 0.1 µm and less; precipitated or/and involved nanosized particles are distributed homogenously on the grain boundaries around refractory phases; refractory compound phases of electrode material could be wetted by the melt of substrate metal. Coatings deposited using those three groups of electrodes materials has a raised hardness, elastic recovery, adhesion strength to substrate, heat resistance, and reduced friction coefficient. Simulations of the polarity mass-transfer coefficient in spark of discharge for micro- and nanostructured electrode materials was carried out using Palatnik’s criteria. Coatings thickness more than 50 µm at high density and lower roughness were achieved due to high erosion energy of anode at high frequency and respectively lower pulse discharge energy. Coatings phase and structure formation on Ti-, Ni-, Fe- substrates are discussed. Examples of successful industrial application of CRAPED technologies are demonstrated.
9:20 AM		B6-3-5 Microstructure and Oxidation Resistance of Ti-B-C, Ti-B-C-N, and Ti-B-C-N-Si Films Deposited by Unbalanced Magnetron Sputtering I.-W. Park, J.J. Moore, B. Mishra (Colorado School of Mines); A.A. Voevodin (Air Force Research Laboratory); K.H. Kim (Pusan National University, Korea); E.A. Levashov (State Technological University/Moscow Institute of Steel and Alloys, Russia) Multifunctional nanocomposite, based on nanocrystalline (nc-) and amorphous (a-) phases, films attract considerable interest to extend the lifetime of cutting tools, press-forming tools and various other mechanical components. Films for most tribological applications require combinations of properties such as a relatively high hardness, high fracture toughness, wear- and oxidation-resistance, and a low friction coefficient. The present work investigates the co-deposition of Ti-B-C, Ti-B-C-N, and Ti-B-C-N-Si nanocomposite films from a composite target of TiB2-TiC and a pure boron doped Si target using DC unbalanced magnetron sputtering in Ar/N2 gas mixtures. The microstructures, mechanical, wear and oxidation properties for the films were investigated in various N and Si contents. The microstructures of the synthesized films were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscope (XPS), high-resolution transmission electron microscope (HRTEM), respectively. Nano-indentation was conducted to assess the hardness and Young’s modulus of the films. Wear- and oxidation-resistance of these films were evaluated using a CETR micro-tribometer and TG-DSC, respectively. In the present work, the comprehensive microstructures and various properties of the films were investigated and correlated with deposition parameters.
9:40 AM		B6-3-6 Microstructure and Mechanical Properties of Cr-B-N and Cr-B-Al-N Coatings Deposited by Unbalanced Magnetron Sputtering W.C. Moerbe (Colorado School of Mines) A range of Cr-B-N and Cr-B-Al-N coatings were deposited using unbalanced magnetron sputtering from CrB2 and Al targets in a reactive argon-nitrogen atmosphere. The structure and properties of the films were investigated using analytical techniques that included XRD, FE-SEM, XPS, nano-indentation, micro-tribometry, potentiodynamic testing, and DTA. The nitrogen content in the Cr-B-N films has a prominent effect upon the mechanical properties. Hardness and Young’s modulus decrease as a function of increasing nitrogen content and increasing amorphous phase content in the films. The friction coefficients of the Cr-B-N coatings were in the range of 0.35 to 0.45 and the wear factors were in the 10-6 to 10-7 mm3 N-1 M-1 range. The addition of Al to the Cr-B-N films has produced coatings with friction coefficients in the 0.35 range. The increase of nitrogen content in the Cr-B-Al-N films has led to an improvement in wear properties and friction coefficient.
10:00 AM		B6-3-8 TiN/AlN Nanomultilayer Coatings With Differrent Thickness Ratio M. Setoyama (Sumitomo Electric Industries, Ltd., Japan) TiN/AlN superlattice has a significant property that its film hardness increases depending on its bilayer period. At the bilayer period of 2.5nm the maximum hardness was obtained and AlN layer formed in a metastable cubic structure phase that is stable under high pressure environment. Because TiN/AlN superlattice has high hardness and high oxidation resistance, it is successfully used as a protective coating for cutting tools. TiN/AlN nanomultilayer films with different bilayer periods and thickness ratios of TiN to AlN each layer was prepared onto cemented carbide substrates by using cathodic arc evaporation. Both Ti and Al metal targets were evaporated simultaneously in nitrogen atmosphere. The thickness ratio of TiN to AlN was changed by each arc discharge currents, and bilayer period was controlled by varying the rotation speed of substrate holder on the rotation table. Film hardness was evaluated with micro Knoop hardness measurement. Film hardness depended on not only bilayer period but also thickness ratio. In the case of the thickness ratio TiN/AlN = 50/50 and 35/65, above 3nm, as the bilayer period decreased, its hardness decreased. At the bilayer period about 2.5nm, the film hardness drastically increased, and then it decreased again under 2.5nm. However, in the case of the ratio TiN/AlN=25/75 and 20/80, AlN layer was thicker, film hardness simply decreased as the bilayer period decreased. Hardness enhanced effect was not appeared.
10:20 AM		B6-3-9 Effect of Carbon on TiAlCN Coating by Reactive Magnetron Sputtering X. Zhang (Southeast University/Colorado School of Mines, China); J. Jiang, Y. Zeng (Southeast University, China); J. Lin, J.J. Moore (Colorado School of Mines) TiAlCN coatings with various carbon contents have been prepared by direct current reactive magnetron sputtering using Ti-Al-C mosaic type targets. Coating’s composition and structure were analyzed by energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The micro hardness and adhesion and tribological performance were measured by micro Vickers tester, scratching tester and ball-on-disc tester respectively. Depending on the carbon concentration, significant changes in the coatings’ microstructure were observed. The hardness of TiAlCN coating increases and then decreases as carbon content increases. Coating prepared by target with 50%vol graphite reaches the max hardness. As carbon content increases, the critical load of TiAlCN coating decreases gradually. Nevertheless, the coating with max hardness has the best scratch resistance under 70 N load. Coating with a maximum hardness and a lowest frictional coefficient was obtained by optimizing the carbon content. The relationships of structure-property-performance by carbon modification were discussed.
10:40 AM		B6-3-10 Magnetron Sputtered Nanocrystalline, Metastable (V,Al)(C,N) Hard Coatings S. Ulrich, M. Stüber, C. Ziebert, H. Holleck (Forschungszentrum Karlsruhe, IMF I, Germany) Nanocrystalline, metastable (V,Al)(C,N) hard coatings with f.c.c structure were deposited by non-reactive r.f.-magnetron sputtering of a ceramic composite target (VC : AlN = 60 mol% : 40 mol%) in a pure argon discharge at 1.1 Pa. The chemical composition of as-deposited coatings was determined by electron microprobe analysis. The nanoscale microstructure of the films was characterized by X-ray and electron diffraction and scanning electron microscopy. The influence of ion bombardment, especially the variation of the argon ion energy (20 eV - 170 eV) during film deposition, as a mean to adjust the adatom surface mobility and surface diffusion, on film properties such as hardness (23.3 GPa - 29.6 GPa), reduced Young’s Modulus (450 GPa - 500 GPa), and adhesion (30 N - 45 N critical load of failure in the scratch test) is discussed in detail. Finally, the conditions for the formation of metastable (V,Al)(C,N) thin film microstructure are described in terms of surface processes during film growth and thermodynamic considerations.