(Ti,Al)N-based hard coatings dominate the market in high-performance cutting. The leading equipment manufacturers have maximized the aluminum share in order to improve film hardness, wear and heat resistance. Still, beyond 75 at.-% Al, a further increase is not useful.

The nanocomposite concept provides a way to break through this dilemma: Embedding nano-crystalline Ti_xAl_1-xN grains in an amorphous Si₃N₄ matrix enables a structure of extremely high hardness (~47-50 GPa) maintained to very high temperatures (up to ~1100°C), even at lower Al contents of e.g. 50%.

Highly ionized plasma is the key to successful cathodic arc deposition of nanocomposites. Today's state-of-the-art industrial PVD units, based on static planar cathodes, limit the maximum useable magnetic field intensity because of the danger of catastrophic target erosion. Dynamic lateral rotating arc cathodes (LARC^(R)) break through this dilemma:

Strong magnetic fields are used to provide a highly ionized plasma without the danger of cutting into the electrode. Thanks to the fast, well-controlled motion of the arc track on the specially shaped cylindrical target, uniform evaporation even of low-melting materials is possible. Target poisoning can be controlled to a so far unmatched extent, and, using Al or Al-Si alloys as targets, advanced coatings can be now deposited within a wide compositional range without cathode changing. Turning the magnetic field creates a VIRTUAL SHUTTER^(R) free of any sensitive mechanical elements. Prior to deposition, the targets are cleaned to the backside, thus avoiding substrate contamination and ensuring optimum adhesion.

Results will be presented on the microstructure and nanomechanical properties of the Platit AlTiSiN nanocomposite coatings. Tests of cutting tool performance will illustrate the potential of this new coating generation in conventional as well as extreme environments.

ICMCTF2003 Tuesday Morning

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