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Titanium aluminium nitride (TiAlN) or aluminium titanium nitride (AlTiN; for aluminium contents higher than 50%) is a group of
metastable In chemistry and physics, metastability denotes an intermediate Energy level, energetic state within a dynamical system other than the system's ground state, state of least energy. A ball resting in a hollow on a slope is a simple example of me ...
hard coatings consisting of
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
and the metallic elements
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
and
titanium Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
. Four important compositions (metal content 100 wt.%) are deposited in industrial scale by
physical vapor deposition Physical vapor deposition (PVD), sometimes called physical vapor transport (PVT), describes a variety of vacuum deposition methods which can be used to produce thin films and coatings on substrates including metals, ceramics, glass, and polym ...
methods: * Ti50Al50N (industrially introduced by the company CemeCoat (now CemeCon) Aachen, BRD, group T. Leydecker ca. 1989) * Al55Ti45N (industrially introduced by the company Metaplas Ionon (now Oerlikon), Bergisch Gladbach, BRD, group J. Vetter ca. 1999) * Al60Ti40N (industrially introduced by the company Kobe Steel, Kobe, Japan, ca. 1992) * Al66Ti34N (industrially introduced by the company Metaplas (now Oerlikon) group J. Vetter ca. 1996). The fundamental reasons why TiAlN coatings outperform pure
Titanium nitride Titanium nitride (TiN; sometimes known as Tinite) is an extremely hard ceramic material, often used as a physical vapor deposition (PVD) coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface prope ...
(TiN) coatings are considered to be: * Increased oxidation resistance at elevated temperatures due to the formation of a protective aluminium-oxide layer at the surface * Increased hardness in the freshly deposited films due to micro-structure changes and solid solution hardening * Age hardening of the coatings at temperatures typical for cutting tools operation due to spinodal decomposition of TiAlN into TiN and cubic AlN The age hardening phenomena has been shown to originate in a mismatch in the quantum mechanical electronic structure of TiN and AlN. The coatings are mostly deposited by
cathodic arc deposition {{Short description, Type of physical vapor deposition technique Cathodic arc deposition or Arc-PVD is a physical vapor deposition technique in which an electric arc is used to vaporize material from a cathode target. The vaporized material then ...
or
magnetron The cavity magnetron is a high-power vacuum tube used in early radar systems and currently in microwave ovens and linear particle accelerators. It generates microwaves using the interaction of a stream of electrons with a magnetic field while ...
sputtering In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and can ...
. Even though most TiAlN and AlTiN coatings are industrially synthesized using alloy targets with specific percentages of aluminium and titanium it is possible to produce TiAlN coatings with pure Al and Ti targets using a cathodic arc deposition technique. TiAlN and AlTiN coatings from pure Al and pure Ti targets by Cathodic arc deposition have been produced industrially by NanoShield PVD Thailand since 1999. By using separate target technology it is possible to offer more flexibility regarding the structure and composition of the coating. Selected properties of Al66Ti34N are: *
Vickers hardness The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. The Vickers test is often easier to use than other hardness t ...
2600 to 3300 HV. * Phase stability ca. 850 °C, start of decomposition to AlN+TiN. * Intense
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
starts at about 800 °C (ca. 300 °C higher than for TiN). * Lower electrical and
thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...
than
TiN Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
* Typical coating thickness ca. (1 to 7) μm One commercial coating type used to improve the wear resistance of
tungsten carbide Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
tools is the AlTiN-Saturn from Sulzer Metaplas.PVD High-Performance Coating
/ref> The coatings are sometimes doped with at least one of the elements
carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
,
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
,
boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...
,
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
and
yttrium Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a "rare-earth element". Yttrium is almost always found in com ...
in order to improve selected properties for specific applications. These coatings are also used to create multilayer systems. For example, they can be used in combination with TiSiXN like those used in the Mpower coating family of Sulzer Metaplas. The coating types mentioned above are applied to protect tools including special tools for medical applications. They are also used as decorative finishes. One derivative of TiAlN coating technology is the
nanocomposite Nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material. The id ...
TiAlSiN (titanium aluminium silicon nitride) which was developed by SHM in the Czech Republic and now marketed by Platit of Switzerland. The nanocomposite TiAlSiN coating exhibits
superhard A superhard material is a material with a hardness value exceeding 40 gigapascals (GPa) when measured by the Vickers hardness test. They are virtually incompressible solids with high electron density and high bond covalency. As a result of their u ...
hardness and outstanding high temperature workability.


References


External links


Nanocomposite AlTiNCO Coatings Deposited by Reactive Cathodic Arc Evaporation


{{Titanium compounds Nitrides Titanium compounds Aluminium compounds