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

Monday, April 27, 1998 8:30 AM in Room Golden West

Monday Morning

Start	Invited?	Item
8:30 AM		B1-1 Plenary Lecture
8:50 AM	Invited	B1-2 Plenary Lecture
9:30 AM	Invited	B1-4 Plenary Lecture
10:10 AM		B1-6 Plenary Lecture
10:30 AM		B1-7 Reactive Sputter Deposition of TiN/C-N and NbN/C-N Nanostructured Multilayers H. Jensen (University of Aarhus, Denmark); J. Sobota (ASCR, Czech Republic); G. Sorensen (University of Aarhus, Denmark) It is observed that friction in dry sliding is dependent on the deposition conditions for reactively sputtered nano structured multilayer coatings of carbon nitride seeded with TiN. These exhibit lower friction than conventional reactively sputtered coatings of titanium carbon nitrides containing the identical elements, but arranged differently. The present contribution will focus on reactive sputtering of nanostructured multilayers with bilayers in the nm region of carbon nitride with TiN and NbN as seeding layers. All multilayers have been deposited using the side by side configuration from concurrently operating targets of carbon and metal. Deposition were performed on a substrate holder rotating between 2 and 28 revolutions per minute. The flow of the reactive gas and the voltage of the sputtering cathodes were measured and used for process control. Stable deposition conditions for obtaining low friction coatings will be reported. The performance testing of the deposited nanostructured coatings will be discussed also including a dynamic wear testing. The relation between wear and adhesion of nanostructured multilayers will be reported and discussed. Particular attention will be given to the multilayer coating adhesion and the friction for sliding with a reciprocating ball of materials such as WC, Si₃N₄ and steel. The perspectives of nanostructured composite coatings as metallurgical coatings will be discussed.
10:50 AM		B1-8 Growth and Mechanical Properties of CN_x / BN:C Nano-Scaled Layered Coatings by Unbalanced Dual Cathode Reactive Magnetron Sputtering T. Berlind, N. Hellgren, M. Johansson, L.G. Hultman, J.-E. Sundgren (Linköping University, Sweden) Nano-scaled layered CN_x/BN:C coatings were deposited by controllably unbalanced dual cathode reactive magnetron sputtering from C (graphite) and B₄C targets. The depositions were made in an Ar/N₂ discharge at substrate temperatures of 300 C and the substrates were held at floating potential (29-34 V). Coatings with compositional periodicities ranging from 0.5 to 10 nm and with a total film thickness of 0.5-1 μm were deposited on Si (001), cemented carbide and high speed steel substrates. By low-angle X-ray reflectivity, multilayer satellite peaks could be observed up to the third order, which indicated that the interfaces between the CN_x and BN:C layers were well defined. Electron microscopy showed a highly textured turbostratic (hexagonal) structure with curved and intersecting basal planes. The chemical compositions were measured by XPS. The nitrogen concentration in the CN_x layers was found to be approx. 12 at.%, which should be compared to approx. 20 at.% for coatings sputtered in pure N₂ discharge under otherwise similar conditions. The carbon concentration in the BN:C layers were found to be approx. 20 at.%, i.e., slightly higher than what previously have been observed. The B/N ratio was found to be about unity. Nanoindentation studies of as-deposited coatings showed elastic recoveries of 80-90% after a 10 mN load. The results indicated that the multilayer coatings were slightly harder and more elastic compared to the single layer CN_x (Ar/N₂ ) and BN:C coatings, respectively. A weak tendency to an increased hardness with decreased periodicity was observed. The higher elasticity of the CN_x coating sputtered in pure N₂ indicated that the properties of the nano-scaled layered CN_x/BN:C can be further improved. Hardness data and tribological evaluation (abrasive wear test) will also be presented. The results regarding structure and mechanical properties of the coatings will be compared with the systems CN_x, BN:C and the ternary BNC.
11:10 AM	Invited	B1-9 Reactive Sputtering of Nanometer-Scale Multilayer Coatings S.A. Barnett (Northwestern University) This talk will review the structure and mechanical properties of nanometer-scale multilayer coatings (superlattices) deposited using reactive sputtering. One type of superlattice considered consists of layers that are both immiscible and have different structures, e.g. Mo/NbN. The immiscibility is of interest since the superlattice structure can exhibit good high-temperature stability. As-deposited Mo/NbN superlattices show large hardness values (~30 GPa) at periods of 1-5 nm, compared with 3 GPa for Mo and 16 GPa for NbN. Annealing of Mo/NbN at 1000ºC yielded little change in the superlattice layer structure, as observed by x-ray diffraction, and hardness actually increased slightly. Another type of superlattice considered is where one layer is forced into a metastable structure by the surrounding layers. One example is AlN/TiN, where AlN layers are in the rocksalt structure for thicknesses up to 2 nm, but transform to the equilibrium hexagonal structure for larger thicknesses. Hardnesses as high as 40 GPa have been reported for superlattices with cubic AlN layers. Another example is ZrO₂/Y₂O₃, where the ZrO₂ layers are cubic for thicknesses < 25 nm. Hardness enhancement by ~25% has been observed in these oxide superlattices. Hardening mechanisms in the above superlattices will be discussed.
11:50 AM		B1-11 Deposition And Characterization of Multi-layered TiN/TiAlN Coatings By Unbalanced Magnetron Sputtering W. Wu (I-Shou University, Taiwan); J.H. Hsieh (Gintic Institute of Manufacturing Technology); C.H. Yu (I-Shou University, Taiwan); C. Liang (Gintic Institute of Manufacturing Technology, Singapore) TiAlN coatings have been known to be superior to other coatings such as TiN and TiCN in protecting tools which may be damaged by high thermal load (high cutting speed). Unfortunately, these coatings normally suffer greater damage than TiN and TiCN in more mechanically influenced processes such as interrupted cutting or slow speed cutting. The present study aims at developing multi-layered TiN/TiCN coatings which may compromise the properties of TiN and TiAlN. Three approaches including shield control, power supply control, and rotational stage control were used to deposit multi-layered TiN/TiAlN coatings using unbalanced magnetron. These coatings were then characterized using XRD, SEM, GDOS, nano-indention system, and tribometer. For tribological testing, a ball-on-disk setup was used with M50 steel and alumina as balls. The load was set at 2.5N through all the tests. It was found that, in general, these multi-layered TiN/TiAlN coatings had lower wear rate than single-layered TiAlN with the sliding speed ranging from 3m/min. to 18m/min. At a sliding speed greater than 12m/min, these coatings also had lower wear rate than TiN. However, at a sliding speed less than 6m/min, the coatings showed poorer wear resistance than TiN coating. To overcome this problem, a thin layer (0.1 mm) of TiCN was coated on a multi-layered coating in an attempt to reduce friction particularly during run-in stage. The result shows that the wear resistance of the TiCN-(TiN/TiAlN) coating was significantly improved especially at low sliding speed.