ICMCTF2006 Session B8-1: Hard and Multifunctional Nano-Structured Coatings

Thursday, May 4, 2006 8:30 AM in Room Golden West

Thursday Morning

Start	Invited?	Item
8:30 AM	Invited	B8-1-1 Materials Aspects of the Nanoscale Thin Film Design H. Holleck, M.A. Stueber, S. Ulrich, C. Ziebert, H. Leiste (Forschungszentrum Karlsruhe, Germany) Background and requirement for a nanoscale thin film design is a specific material selection combined with well-adjusted deposition conditions. Thermodynamics of the thin film material systems as well as kinetics determined by the deposition parameters allow tailoring the thin film properties and performance. Material combinations from the groups of metallic, covalent und ionic hard materials will be discussed with respect of meeting the requirements to generate a specific thin film nanostructure with a multifunctional property profile. The following thin film concepts will be discussed in detail with respect to constitution and properties: (i) By nanokinetics controlled new metastable multifunctional film materials (examples: TiAlNO, TiAlCO, TiSiNO, TiSiCO) (ii) Different natures of nanostructured multilayer film (examples: nanostabilization of new thin film structures in combinations like TiN/AlN and TiN/SiN_x, interface controlled multilayer films like TiN/ZrN, superlattice films) (iii) Multifunctional nanocomposite films (examples: TiAlN/C, TiC/C).
9:10 AM		B8-1-3 Grain Size Evaluation of Pulsed TiAlN Nanocomposite Coatings for Cutting Tools K. Bobzin, E. Lugscheider, M. Maes, P. Immich (RWTH Aachen University, Germany) Nowadays advanced TiAlN coatings enable high performance and high speed cutting. A side from excellent coating adhesion at the cutting edges and choice of material, a fine grained PVD coating is the enabler for these high performance cutting operations. Isotropy and composition of the coating is of vital importance for the performance of these coatings. On industrial scale equipment, composition (Ti-Al ratio), crystallite size and orientation are altered by changing pulse sequence and duty cycle. The synthesized coatings were then analyzed by common thin film and application oriented techniques. In order to determine the crystallite size Debye-Scherer, Warren-Averbach method and TEM analysis are applied. Finally the performance of these coating was evaluated in cutting tests.
9:30 AM		B8-1-4 Hardening Effects in Annealed EB-PVD Nanocomposite TiAlBN Films C.G. Rebholz (University of Cyprus); P.H. Mayrhofer, J.M. Schneider (RWTH Aachen University, Germany); M.A. Monclus, M.A. Baker (University of Surrey, United Kingdom); A. Leyland, A. Matthews (The University of Sheffield, United Kingdom) TiAlBN films were deposited by electron beam evaporation from a twin crucible source onto Si (100), AISI316 and M2 substrates in order to study the influence of the chemical composition and structure on the thermal stability. X-ray electron spectroscopy (XPS) studies were performed to investigate the phase composition and bonding. The film nanostructure and mechanical properties in both as-deposited and annealed states were determined using X-ray diffraction (XRD) in combination with transmission electron spectroscopy (TEM) and nanoindentation measurements. The formation of nanocrystalline (Ti,Al)N grains separated by an intergranular amorphous BN phase was observed. Films consisting of 90 mol% (Ti,Al)N and 10 mol% BN with an average (Ti,Al)N grain size of 26 nm (and interganular separation of around 3 nm) showed hardness and elastic modulus values of 40 and 360 GPa, respectively. Vacuum annealing experiments revealed an increase in hardness for all films as a result of a changed nanostructure. Independent of the composition, all films showed thermal stablility at temperatures in excess of 900°C. Due to their excellent mechanical and thermal properties TiAlBN films exhibit a huge potential for severe applications.
9:50 AM		B8-1-6 CrAlYN/CrN Superlattice Coatings Deposited by the Combined High Power Impulse Magnetron Sputtering / Unbalanced Magnetron Sputtering Technique P.Eh. Hovsepian, C. Reinhard, A.P. Ehiasarian (Sheffield Hallam University, United Kingdom) The CrAlYN/CrN represents a new generation of Ti-free PVD coatings tailored to serve high temperature applications such as dry high speed machining and protection of special grades aerospace and automotive alloys against environmental attack. The novel High Power Impulse Magnetron Sputtering (HIPIMS) technique was used for substrate pre-treatment (etching) followed by coating deposition utilising Unbalanced Magnetron Sputtering (UBM). HIPIMS was operated at peak power densities of 2 kWcm^-2 and high degree of ionisation of Cr was observed by OES. The employment of HIPIMS resulted in smooth (Ra = 0.03 µm), and well adherent films with typical scratch adhesion critical load values on HSS of L_C = 61 N. Low angle XRD analysis showed that the coating has a nanoscale multilayer (superlattice) structure with typical bi-layer thickness of 4.3 nm. XTEM observations confirmed this result and further revealed the dense, growth defect free structure of the coating due to the HIPIMS etching. CrAlYN/CrN combines high hardness of HK_25g = 3500 with low coefficient of friction of 0.55 when sliding against Al₂O₃ counterpart and exceptionally low sliding wear coefficient of 2.87x10¹⁷ m³N^-1m^-2, which is comparable to that of TiAlN/VN and Me-Carbon films. In dry high speed milling (V_cutting = 385 m.min^-1) of hardened A2 tool steel (HRC = 58), 8 mm cemented carbide ball nosed end mills coated with CrAlYN/CrN outperformed TiAlCrYN, which is one of the market leading coating dedicated to this application. When the test is carried out at high end cutting speeds of 500 m.min^-1 this difference in the performance becomes even more pronounced, (factor of 3 longer life time), demonstrating the excellent quality of CrAlYN/CrN films.
10:10 AM		B8-1-7 Comparison of Cr_1-xAl_xSi_yN and Ti_1-xAl_xSi_yN Coatings Prepared by Arc Evaporation P. Karvankova, A. Karimi (EPFL, Switzerland); O. Coddet, T. Cselle, M. Morstein (PLATIT, Switzerland) Hardness, biaxial stress and morphology of coatings deposited on cemented carbide using the lateral rotating arc cathode (LARC^®) process were investigated. The response of these properties, as well as coating texture, lattice parameter, crystallite size and XRD phase composition, to a variation of both Si content and composition x, was measured. It was confirmed that the solubility of the cubic AlN phase in CrN is larger than in TiN. Increasing aluminium content in Ti_1-xAl_xN and Cr_1-xAl_xN coatings caused an increase of the hardness due to solid solution hardening and development of intrinsic stresses. A decrease of hardness and stress for larger x (x > 0.5 for Ti_1-xAl_xN, x > 0.65 for Cr_1-xAl_xN) was observed due to segregation of hexagonal AlN phase. The crystallite size decreases with increasing aluminium content and is smaller for Ti_1-xAl_xN coatings. The stress-free lattice parameter decreases with increasing Al incorporation into the cubic TiN or CrN phase, yet grows with the addition of Si. Increasing the Si content yields smaller crystallites and changes the coating structure from columnar to equiaxed. The biaxial compressive stress becomes lower for Cr_1-xAl_xSi_yN and higher for Ti_1-xAl_xSi_yN, while the hardness is only weakly affected for x < 0.5. The influence of coating nanostructure and mechanical properties on the cutting performance will be discussed.
10:30 AM		B8-1-8 Microstructures, Mechanical Properties, and Tribological Properties of Ti-Si-B-C-N Nanocomposite Films by DC Unbalanced Magnetron Sputtering I.W. Park, A.O. Kunrath, D. Zhong, J.J Moore (Colorado School of Mines); A.A. Voevodin (Air Force Research Laboratory); K.H. Kim (Pusan National University, Korea) Nanocomposite coatings have been extensively studied due to their potential for achieving very high hardness, oxidation resistance and lubrication characteristics, in an effort to improve wear behavior of tools and components in several applications. Coatings containing nanoscale features may be produced by alternatively depositing nanolayers of different materials in a laminated structure or by co-depositing immiscible phases. Nanocomposite films produced by co-deposition may comprise only nanocrystalline phases (nc-nc) or nanocrystalline and amorphous phases (nc-a). The successful production of hard isotropically nanostructured films containing crystalline and amorphous phases depends on the appropriate size and distribution of these nanoscale phases. The present work investigates the co-deposition of Ti-Si-B-C-N nanocomposite films from a composite target of TiB₂-TiC and a pure boron doped Si target using DC unbalanced magnetron sputtering in an Ar/N₂ gas mixture. The microstructure and mechanical properties for the films were investigated in various Si target powers and were evaluated by X-ray diffractometer (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscope (XPS), high-resolution transmission electron microscope (HRTEM), respectively. Nanoindentaion was conducted to assess the hardness and Youngâ?Ts modulus of the Ti-Si-B-C-N films. Wear resistance and coefficient of friction of these films were evaluated using a CETR micro-tribometer and a Teer Coatings scratch/adhesion tester. This paper will present the effects of Si content on the microstructure, hardness, and tribological properties of a DC unbalanced magnetron sputtered Ti-Si-B-C-N films.
10:50 AM		B8-1-9 Growth and Characterization of Epitaxially Stabilized SiN_x in TiN/SiN_x Multilayer Films H. Söderberg (Luleå University of Technology, Sweden); L. Hultman, J. Birch, A. Flink (Linköping University, Sweden); M. Odén (Luleå University of Technology, Sweden) Coatings deposited from the Ti-Si-N system have gained more attention during the recent years. Most studies have been focusing on nanocomposite coatings whereas studies on multilayer coatings are rarer. However, the 2-dimensional geometry within a multilayer film should produce an easier interfacial analysis compared to the 3-dimensional geometry within a nanocomposite. Thus, in this work multilayered films of TiN and SiN_x have been deposited by reactive magnetron sputtering. As substrates both single crystal Si-wafers and single crystal MgO have been used. The microstructure and mechanical properties were evaluated through x-ray diffraction, cross sectional transmission electron microscopy, and nanoindentation. A first study with Si substrates suggested an epitaxial stabilization of cubic SiN_x or SiN rich phase on polycrystalline TiN for thin interlayers, below 8Å, whereas amorphous SiN_x will form with increasing layer thickness, 8Å and above. The second study with MgO substrates was carried out in order to examine the possibility of depositing single crystal TiN/SiN multilayers with increasing SiN_x layer thickness. A buffer layer of TiN was first deposited to provide a good quality crystal for the multilayer to grow on. The subsequent depositions of the multilayers were done within a range of different deposition conditions in order to find the best conditions for epitaxial growth, e.g. different layer thicknesses, substrate temperatures, and bias voltages during SiN_x deposition. High resolution x-ray diffraction (HRXRD) revealed a well defined crystal structure. The diffraction pattern showed superlattice peaks, but also fringes in between the superlattice peaks suggesting high quality superlattices. The results show an epitaxial stabilization of SiN_x within the multilayers. This stabilization is discussed in terms of surface and total energies and that the stabilization is due to a decrease of the system energy. In addition, the affect of epitaxial growth on hardness is also addressed.
11:10 AM		B8-1-10 Pulsed Sputter Deposition of Binary and Ternary Oxides in the Systems Si-O, Cr-O and Al-O R. Cremer, J. Mueller, H.-G. Fuss (CemeCon AG, Germany) In this study the high ionization pulsing technique is used to deposit non-conductive thin films of alumina, chromia, silica and mixed oxides thereof on temperature sensitive substrates. Furthermore the effects of deposition parameters and conditions on the coating morphology, evolution of microstructure and mechanical properties will be described. A focus will be put on the investigation of miscibility gaps as well as interstitial solutions by means of x-ray diffraction analysis. It will be shown that sophisticated PVD pulsing techniques allow for deposition of high quality alumina and mixed oxide films in general, which offer high adhesion, best surface finish and superior mechanical properties for highest demanding metal cutting applications, e.g. stainless steel.
11:30 AM		B8-1-11 Tribological Performance of Nano-Structured Ti-Si-N Films Syntheized by Cathodic Arc Evaporation S.-M. Yang (National Chung Hsing University); Y.-Y. Chang (Mingdao University, Taiwan); W.-T. Wu (Industrial Technology Research Institute, Taiwan); D.-Y. Wang (Mingdao University, Taiwan) Nanocomposite Ti_xSi_1-xN coatings have recently attracted much interest because of their high hardness, wear resistance, and good thermal and chemical stability. In this study, Ti_xSi_1-xN coatings were synthesized by a plasma enhanced cathodic arc evaporation process with Ti80Si20 alloy targets. Reactive gas (N2) activated by the TiSi alloy plasma in the evaporation process was used to form the nanocomposite Ti_xSi_1-xN coatings. Deposition was carried out under various conditions to investigate the effects of different operational parameters on film structure and mechanical properties. The crystallographic texture of the deposited film was characterized using glancing incidence X-ray diffraction (GIXRD), while the structure was studied using field emission scanning electron microscopy (FESEM) and cross-sectional transmission electron microscopy (TEM). It showed the nano-grain structure transformation by the addition of Si to TiN films. Scratch tests and Rockwell indentation were performed to determine the interfacial adhesion between substrate and Ti-Si-N films. Mechanical properties, such as hardness and elastic modulus, were measured by nano-indentation test. Sliding friction and wear investigations were performed by using a ball-on-disc test. It has been found that the structural and mechanical properties of the films were correlated with the addition of silicon and nitrogen partial pressure.