ICMCTF2004 Session B8-2: Hard and Multifunctional Nano-structured Coatings

Tuesday, April 20, 2004 1:30 PM in Room Golden West

Tuesday Afternoon

Start	Invited?	Item
1:30 PM	Invited	B8-2-1 Controlling Phase Formation and Separation in Nanocomposite Carbide Coatings for Improved Tribological Performance J.E. Krzanowski (University of New Hampshire) Multiphase nano-composite coatings have the potential to improve the performance of tribological coatings by augmenting their properties and imparting new multi-functional characteristics. The application of these coatings will require careful control and reproducibility of the coating microstructure. In general, the appropriate structure must be obtained during the coating deposition process. A host of interacting factors must be considered, including the energetics of the deposition process, deposition rate, substrate temperature as well as the thermodynamic driving force for phase separation. In this talk, examples will be given from our work on composite films consisting of transition metal carbide/silicon carbide, transition metal carbide/silver, and MoS₂/metal components. These examples will demonstrate the effects of surface and bulk diffusion, and the enthalpy of mixing, on the deposited film structure.
2:10 PM		B8-2-3 Smart Structuring of High-performance Nanocomposite Coatings M. Morstein, O. Coddet, T. Cselle (Platit AG, Switzerland); B. Torp (Platit Scandinavia, Denmark); M. Jilek, P. Holubar (PIVOT, Czech Republic) Ceramic-ceramic nanocomposite PVD coatings successfully challenge Ti,AlN-based thin films in today's high-performance tooling applications. The family of nACo^(R) Al_xTi_1-xN/Si₃N₄ industrial arc coatings features hardness-toughness optimization to maximize their wear-resistance. These materials have repeatedly field-proven their excellent resistance to extreme environments, thanks to a smart nanostructural and chemical stabilization. The Platit LARC^(R) deposition technology, based on lateral rotating arc cathodes, allows the selection of optimum plasma conditions for deposition of such nanocomposites. An update will be given on the recent progress in nanocomposite coatings development. Examples of practical usage will be presented with a particular emphasis on high-performance applications such as hard milling. We will furthermore discuss the relative importance of nano- and microstructural stabilization, and outline the influence of film chemistry on both high-temperature oxidation resistance and frictional behavior of nanocomposite coatings.
2:30 PM	Invited	B8-2-4 Shape Memory Materials for Tribological Applications Y.T. Cheng, W. Ni (General Motors Research and Development Center); D.S. Grummon (Michigan State University) Although the macroscopic shape memory (SM) and superelastic (SE) effects are well known, very few studies have been conducted to investigate the SM and SE effects at the micro- and nano-meter length scales. Recently, we have investigated these effects in NiTi alloys and thin films by instrumented indentation experiments. The SM effect was quantified by the magnitude of the depth recovery of indents upon heating; the SE effect was determined by the ratio of reversible work to total work. We show that SM and SE effects exist under both spherical and pyramidal indenters for a wide range of indentation loads and depths. We have also performed scratch adhesion and wear studies of these materials. These studies provide new insights into the mechanisms of SM and SE effects at multiple length scales and illustrate the possibilities of using shape memory alloys and thin films as self-healing tribological surfaces and durable interfaces.
3:10 PM		B8-2-6 Effect of B Content on Microstructure and Nanohardness of Ti-B-N Thin Films S. Ping, Y.H. Lu, H. Chen (City University of Hong Kong) Effects of boron (B) content on microstructure and nanohardness of Ti-B-N coatings had been studied using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), Pole Figure, FT-IR, and X-ray photoelectron spectroscopy (XPS) techniques. The results indicated that the Ti-B-N thin films exhibited a multiphase microstructure; its phase constitution was dependent upon B content. The thin films containing small amount of B showed columnar microstructure including TiB, BN and TiN bondings as revealed by XPS results. Upon increasing B content, TiB gradually transformed to TiB₂, until a TiN/TiB₂/BN nanocomposite microstructure was formed. Simultaneously, the fraction of crystalline TiN phase decreased, and the fraction of other phases (TiB₂, BN) increased. Accompanied with it was the decrease of the grain size of crystalline TiN phase, and finally an amorphous-like microstructure formed. But some non-reacted TiB₂ phase still existed. Although (111) orientation of crystalline TiN was dominant in all samples studied, the orientation gradually changed from 111 to a mixed texture with increasing B content. The nanohardness increased with increasing B content, and reached its maximum at about 15 mol% B content, corresponding to multiphase microstructure possessing 27 mol% amorphous phase. The stabilizing effect of B and strengthening mechanism of microstructure were also discussed.
3:30 PM		B8-2-7 Effect of the Si Content on the Mechanical Properties of Nanocomposite TiAl-Si-N Coatings Synthesized using a Closed Field Unbalanced Magnetron Sputtering G.S. Kim, S.Y. Lee (HanKuk Aviation University, South Korea); J.H. Hahn (Korea Reserch Institute of Sandards and Science, South Korea) PVD hard coatings such as TiN, CrN, ZrN and TiAN have been successfully applied to molds, punch, cutting tools and other machine parts to improve their lifetime for over two decades. The current interest in the hard coatings has been concentrated on the nanostructured coatings with hardness above 40 GPa, so called superhard coatings. In this work, the superhard nanocomposite coatings of TiAl-Si-N system were synthesized and their mechanical properties enhanced by the variety of Si content in the TiAlN coating were reported. The coatings were deposited on the substrates of Si(100) and plasma nitrided AISI H₁₃ steel using a closed field unbalanced magnetron sputtering with separate TiAl and Si targets and characterized by AES, XRD, TEM, Nanoindentation and wear test in terms of chemical composition, crystal orientation, structure and mechanical properties. The results of nanoindentation test showed that TiAl-Si-N coatings have the superhardness above 45 GPa. Also their resistance was largely increased than that of the TiAlN coating. These enhancements of mechanical properties in the TiAl-Si-N coating system could be attributed to Si doping effect, which has reduced the TiAlN grain size. Detailed analysis results of TiAl-Si-N coating will be presented.
3:50 PM		B8-2-8 Effect of Ti to Al Ratio on the Crystal Structure and Mechanical Properties of TiAlN-CrN Superlattice Coating Prepared by D.C. Magnetron Sputtering J. K. Park, H. J. Park, Y. J. Baik (Korea Institute of Science and Technology, South Korea) Recently, many kinds of nanomultilayer coatings with superlattice have been widely investigated, because of the excellent mechanical properties such as hardness and corrosion resistance. TiAlN was known to have excellent mechanical properties such as high hardness and oxidation resistance, and thus has been adopted as main coating materials for cutting tools. TiAlN based superlattice coating has also been widely studied for the much improvement of machining performance of cutting tools. Although the effect of Ti to Al ratio on the phase, structure, and mechanical properties of in the TiAlN film has been reported, such an effect on the TiAlN based nanomultilayer was not yet clearly shown. In this study, the effect of Ti to Al ratio of the TiAlN film layer on the structure and mechanical properties of TiAlN based superlattice coatings has been investigated. The TiAlN-CrN was chosen as nanomultilayer system and deposited on M2 HSS by D.C. magnetron sputtering. The period of nanomultilayer was controlled by changing rotastion speed of substrate holder. Two TiAl alloy targets of the compoaition 75:25 at.% and 50:50 at.% were used. Reactive gas was N₂and Ar and the N₂/Ar volume ratio was 0.67. The phase, structure, residual stress and mechanical properties such as hardness, adhesive strength of the obtained films were measured. The effect of Ti to Al ratio on the phase, structure, and mechanical properties of in the TiAlN-CrN suprelattice coatings will be discussed.