Papers

ICMCTF2009 Session B1-1: Sputtering Coatings and Technologies

Wednesday, April 29, 2009 10:20 AM in Room Golden West

Wednesday Morning

Start	Invited?	Item
10:20 AM		B1-1-9 Composition-Property Relations of Reactive Magnetron Sputtered VC_xN_1-x Coatings N. Fateh, C. Mitterer (University of Leoben, Austria) There is a growing technological interest in the use of transition metal nitrides and carbides due to their unique properties such as high hardness and wear resistance. The aim of this work was to investigate the structural and mechanical properties of VC_xN_1-x films with x ranging from 0 to 1 by varying the flow ratio between the reactive gases. The coatings were grown on silicon and high-speed steel substrates using dc magnetron sputtering from V targets in an Ar/N₂/C₂H₂ atmosphere at a substrate temperature of 500°C. According to X-ray diffraction analysis, VN and VC coatings exhibit a polycrystalline fcc structure where the VC film shows a (200) preferred orientation. XRD patterns of VC_xN_1-x coatings indicate broad peaks positioned between VN and VC giving evidence for the formation of a single-phase VC_xN_1-x solid solution with no preferential orientation. Cross-sectional scanning electron microscopy analysis shows a dense columnar structure for all investigated coatings. Nanoindentation yielded a hardness increase with increasing C content reaching a maximum at x ~ 0.4 while for higher carbon content a decrease in hardness was found. Dry sliding ball-on-disc tests against alumina balls in ambient air showed promising friction and wear behaviour, indicating high application potential of coatings within the V-C-N system.
10:40 AM		B1-1-10 Experimental and Computational Study on the Phase Stability of Cubic Al Containing Transition Metal Nitrides F. Rovere, M. to Baben, S. Ershov (RWTH Aachen University, Germany); H.-G. Fuss (CemeCon AG, Germany); P.H. Mayrhofer (Montanuniversität Leoben, Austria); D. Music, J.M. Schneider (RWTH Aachen University, Germany) Al-containing cubic transition metal (TM) nitrides, where Al substitutes for TM (i.e., TM_1-xAl_xN), exhibit remarkable chemical and physical properties. To tailor the performance of such complex multi-component systems for industrial demands the identification of the physical and chemical mechanisms defining the phase stability of cubic TM_1-xAl_xN is crucial. As obtained by x-ray diffraction analysis, the maximum AlN (x) solubility in single phase cubic Ti_1-xAl_xN, V_1-xAl_xN, and Cr_1-xAl_xN magnetron sputtered films is 0.52±0.02, 0.58±0.02, and 0.71±0.02, respectively. During annealing in Ar atmosphere to 1600°C with a heating rate of 20 K/min, precipitation onset of hexagonal AlN is observed at ~900, 1100, and 1200 °C for Ti_0.5Al_0.5N, V_0.5Al_0.5N, and Cr_0.5Al_0.5N, respectively. Consequently, we find that the overall phase stability of the cubic TM_1-xAl_xN increase s to higher Al-contents and higher temperatures with increasing TM valence electron concentration (VEC). However, the resistance against nitrogen-release decreases with increasing TM VEC, as confirmed by thermo gravimetric data indicating increased mass loss due to nitrogen release of ~2, 5, and 13 wt% for Ti_0.5Al_0.5N, V_0.5Al_0.5N, and Cr_0.5Al_0.5N, respectively, after annealing to 1600°C. These experimental findings are supported by complementary first principle investigations of the individual contributions of electronic configuration and lattice mismatch on the phase stabilities of ternary cubic TM_1-xAl_xN compounds with TM = Sc, Ti, V, Cr, Y, Zr, Nb, and Mo.
11:00 AM		B1-1-11 Combinatorial Sputter Deposition for Thin Film Materials Selection and - Design J.M. Schneider (RWTH Aachen University) Combinatorial techniques are well established in pharmaceutical research for rapid screening and assessment of drugs. During the last decade combinatorial techniques were also used in materials science searching for new materials with attractive magnetic, ferroelectric, and catalytic properties. The assessment of structural materials has also been reported. Combinatorial magnetron sputtering was applied to create materials libraries for the rapid investigation of the correlation between chemical composition, structure, and properties of the as deposited thin films. These correlations are the basis for knowledge based materials selection and - design. Examples discussed in this paper include Cr₂AlC, V₂AlC and Ge-Sb-Te based materials. Furthermore the effect of composition on the stability of CrAlN is presented. To investigate the feasibility of a recently suggested synthesis pathway for MAX phases based on intercalation of sub-stoichiometric transition metal carbides by Al, bi-layers consisting of Ti-C layers with a composition gradient and Al layers have been deposited by combinatorial sputtering. The as deposited bi-layers were then annealed and the formation of a phase mixture containing Ti₂AlC was observed. These examples underline the potential of combinatorial thin film synthesis techniques for the rapid assessment of composition-structure-property relationships enabling efficient materials selection and - design.