ICMCTF1998 Session B1-2: Sputter Techniques & Deposition of Multi- & Nano-scaled Layered Coatings

Monday, April 27, 1998 1:30 PM in Room Golden West

Monday Afternoon

Time Period MoA Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF1998 Schedule

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1:30 PM B1-2-1 Improvements of Unbalanced Magnetron TiAlN Coatings by the Incorporation of Low Concentration Yttrium
W.-D. Münz (Sheffield Hallam University, United Kingdom)

TiAlN coatings have been known since the mid 1980's to exhibit high resistance against oxidation and abrasive wear [1]. However, only recently an industrial breakthroguh has been achieved promoted by the progress in dry, high speed machining using speed machine tools equipped with PVD coated cemented carbide cutting tools including solid carbide end mills and drills. Today TiAlN coatings are routinely produced by magnetron sputtering and cathodic arc evaporation.

A two fold improvement of TiAlN coatings has been developed by the incorporation of typically 2 At % Y into the coating. Ti0.43Al0.52Cr0.03Y0.02N coatings deposited by the combined steered arc/unbalanced magnetron deposition technique are characterised by an extremely fine grained equi-axed micorstructure [2] and both an enhanced compressive stress (7 Gpa) and hardness (HK 2700). The incorporated Y enhances [1] the high temperature oxidation resistance still further and [2] stabilises coating/substrate interface by suppressing the diffusion e.g. of iron and chromium through the film. In fact At % Y containing TiAlN coatings are thermally stable up to approx. 900 °C.

Cemented carbide tools coated with Tio.43Al0.52Cr0.03Y0.02N may be operated in dry cutting of die steels with up to Hrc65, cutting speeds up to 25000 rpm and linear feeds up to 10 m/min.

[1] W.-D./ Münz, J. Vac. Sci. Technol., A4 (1986) 2717

{2] L.A. Donohue, I.J. Smith, W.-D. Münz, I. Petrov. J.E. Greene, to be published in Surf. Coat. Technol.

2:10 PM B1-2-3 Structure, Mechanical and Tribological Properties of Sputtered TiAlBN Coatings Deposited at Different Substrate Temperatures
C. Rebholz, A. Leyland (University of Hull, United Kingdom); A.A. Voevodin (Wright-Patterson Air Force Base); A. Matthews (University of Hull, United Kingdom)

TiAlxByNz coatings (with x = 0.1-0.8, y = 0.2-0.5, z = 0-0.8)have been synthesised by reactive magnetron sputtering in an Ar/N2 plasma at temperatures between 150 and 400 degrees C. Previous studies of Ti-B-N coatings 1, consisting of the TiN, BN and TiB2 phases, showed a progressive increase in hardness from 18 to 40 GPa in the same temperature range. Previously hardness values of up to 20 GPa were reported for TiAlxByNz coatings deposited at 200 degrees C 2. The goal of this investigation was to study in detail the influence of the temperature on the structural, mechanical and tribological properties of these coatings.

The composition of the films was determined by Auger Electron Spectroscopy and Glow Discharge Optical Emission Spectroscopy; chemical state information was gathered by X-ray Photoelectron Spectroscopy. Glancing-angle X-ray Diffraction was used to evaluate the lattice parameter and peak shape parameters, which determine coating micro- and macro-stresses, whilst Scanning macro-stresses, whilst Scanning Electron Microscopy techniques were used to evaluate coating morphology and topography. Knoop microhardness (HK), elastic modulus by Ultrasonic Surface Acoustic Waves, Rockwell ‘C’ indentation and scratch adhesion, dry sliding pin-on-disc and reciprocating wear, ball-on-plate impact and abrasive wear wheel tests were performed to evaluate the mechanical properties of the coatings.

Previous results 2 showed that high hardness values can be obtained from a number of ternary/quaternary compositions, and that coating performance can be optimised in terms of a hardness/toughness compromise if the content and distribution of ‘soft’ phases such as Ti or h-BN can be controlled; these effects are further examined with the modified set of coatings reported here.

1 L.Chalex-Combadiere and J.Machet, Study of the deposition process of TiBN films obtained by d.c. magnetron sputtering, TATF’96 Proceedings, supplement ‘Le Vide science, technique et applications’ no 279 Janvier-Fevrier-Mars 1996, 116-119. 2 C.Rebholz, H.Ziegele, J.M.Schneider, A.Leyland, S.L.Rohde and A.Matthews, Structure, mechanical and tribological properties of sputtered and elecron-beam evaporated PVD hard coatings within the TiB, TiBN and TiAlBN systems, AVS’97 Proceedings, 20-24 October 1997, San Jose, USA.

2:30 PM B1-2-4 Sputter Deposition of c-MoTiN
D. Duerig, E. Bergmann, M. Voinov (Ecole d'Ingenieurs de Geneve, Switzerland)
Recently the phase diagram of vapor deposited mixtures of titanium nitride and molybdenum nitride has been investigated by C.Wiemer et al.. They used an arrangement of two sputter sources with different targets to produce coatings of various compositions.They found, that the admixture of titanium nitride allows the stabilisation of a cubic phase of molybdenum nitride w ith interesting mechanical properties. We have used an industrial sputter process with alloyed targets that can be used for tool coating. The transition from the hexagonal to the cubic phase at a titanium content of .2 is confirmed. First results on wear properties in model tests and tools are also presented
2:50 PM B1-2-5 Nanoscaled Single and Multilayer Hard Coatings - State of the Art and Prospects
H. Holleck, H. Leiste, S. Ulrich (Forschungszentrum Karlsruhe, Germany)
Nanoscaled coatings can be subdivided into nanostructured multilayer films, nanomodulated superlattice films, nanocrystalline films and nanostabilized single and multilayer films. Aside from materials selection and deposition characteristics, the interface volume, grain size, single layer thickness, surface and interface energy, texture and the epitaxial stress and strain are the principal factors which determine constitution, properties and performance of these coatings. The functional and structural design of multilayer coatings can result in tailored multifunctional coatings as it is shown for nanoscaled TiN/TiAlN, TiN/MoS2 and TiC/C multilayer films. The modulation of composition and structure and the influence on the properties are demonstrated for TiC/TiN and TiC/TiB2 multilayer films in dependence on the modulation period. The influence of epitaxial strain with respect to the thermodynamic and kinetic film modelling is qualitatively discussed. Nanocrystalline coatings ( e.g. TiC/C or TiN/MoS2 films) are well suited to combine film materials with extremly different bonding characteristics to a multifunctional composite coating. New structures for thin film materials can be stabilized by epitaxial growth in nanostabilized multilayer coatings. The stabilization of fcc AlN, fcc SiC, crystalline C3N4 and wurzite type BN are examples for materials which operate sucessfully or are in the state of development.
3:30 PM B1-2-7 Recent Progress in the Superhard Nanocrystalline Composites Towards their Industrialization and Understanding of the Origin of the Superhardness
S. Veprek, P. Nesladek, A. Niederhofer, F. Glatz (Technical University Munich, Germany)
The search for superhard materials (hardness≥50 Gpa ~ 5000 kg/mm2) concentrates on the polycrystalline Diamond, c-BN, C3N4 and multilayers. Recently, we have developed a new concept for the design of superhard nanocrystalline composites and verified it on several nc-MenN/a-Si3N4 systems (Me= Ti, W, V). These materials consist of a nanocrystalline hard transition metal nitride embedded into ≤ 1nm thin matrix of a-Si3N4. Unlike pure nanocrystalline metals and the multilayers which show softening when the crystallite size or lattice period decreases below 5-6 nm, the hardness of the composites strongly increases with decreasing crystallite size in that range. These results show the crucial importance of the nature of the nc-MenN/a-Si3N4 interface, and it opens up challenging questions regarding the origin of the superhardness in these composites which clearly differs from that in conventional materials. In the present paper we shall report on the progress achieved in the development of the plasma CVD technique for coating of non planar substrates including the design of a new reactor and related technical problems. We shall also report on the progress in the understainding of the phenomena associated with the stability of the nanostructure and the origin of the high hardness of these materials. Results available so far show that the nanostructure is stable upon half hour isochronal annealing up to 1100oC. The absence of Ostwald ripening under these conditions indicates a thermodynamics stability of these nanostructures. These problems will be discussed in context of some recent publications from other groups.
4:10 PM B1-2-9 Plasma Diagnostics in a Triode Ion Plating System
S. Wouters, S. Kadlec, C. Quaeyhaegens, L.M. Stals (Limburgs Universitair Centrum, Belgium)

Triode ion plating is a well known physical vapor deposition technique for the production of hard coatings like TiN, Ti(C,N), (Ti,Al)N, CrN, etc. ... In triode ion plating the four most important process parameters are: (1) low voltage arc current, (2) high voltage electron gun current, (3) total pressure and (4) substrate voltage. To investigate the influence of these process parameters on the plasma parameters and the energy spectra of ions and neutrals, a flat Langmuir probe was positioned in the main argon plasma body. Furthermore, an energy- and mass-analyzer was oriented to the crucible during the evaporation of titanium without reactive gases.

The substrate bias had no significant influence on the plasma parameters and the energy spectra. The HV electron gun, used to melt the titanium, changed the plasma parameters only at high current values, but the energy spectra of the Ti ions changed drastically. The LV arc current and the total pressure were the main process parameters that did effect both the probe characteristics and the energy spectra of ions and neutrals.

4:30 PM B1-2-10 Influence of Ion Bombardment of Structure and Properties of Unbalanced Magnetron Grown CrNx Coatings
D.B. Lewis (Sheffield Hallam University, United Kingdom); T. Hurkmans (Hauzer Techno Coating Europe, The Netherlands); J.S. Brooks, W.-D. Münz (Sheffield Hallam University, United Kingdom)

Under well controlled reactive unbalanced magnetron sputtering conditions CrNx coatings can be reproducbly deposited as Cr, Cr+N Cr2N and CrN phases and mixtures of Cr+N and Cr2N as a function of the nitrogen content [1]. The structures and properties can be further influenced by variation of bias voltage and bias current density. At floating potential (UB = -25 v) the lattice parameter coincides with that of the bulk value for CrN and the compressive stress approaches almost zero Gpa. Increasing the negative bias voltage to -200 V a steep increase of the lattice parameter together with an increase in the stress to only 1 Gpa um-1 at UB = -200 V was obsrved. In parallel a change in texture was observed. At bias voltages the {200} becomes the major texture. Increasing the bias current density leads also to an increase in the lattice parameter and internal stress from approximately zero Gpa to 1.13 Gpa um-1 at a bias current density of 6 mA cm-2. Increasing ion bombardment densifies the coating as can be observed from the increase of HV 2120 at 1 mA cm-3 to HV 2440 at 6 mA cm-3 at a bias voltage UB = -100 V. The ion energy (bias voltage) obviously influenced the hardness more than the ion flux (bias current density).

At UB = 0 a hardness value of HV 1290 was observed in contrast to HV 2200 at UB = -200 V. SNMS depth profile analysis revealed an extremely uniform homogenous nitrogen composition over the total coating thickness. Whereas the variation of the bias current density hardly influenced the amount of nitrogen incorporated, a slight minimum in the nitrogen concentration was observed at Ub = -50V to UB = -100 V.

Time Period MoA Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF1998 Schedule