Titanium aluminium nitride
Encyclopedia
Titanium aluminium nitride (TiAlN) or aluminium titanium nitride (AlTiN for aluminium contents higher 50 at.%) stands for a group of metastable hard coatings consisting of the metallic elements aluminium
, titanium
and nitrogen
. Four important compositions (metal content 100 at.%) are deposited in industrial scale by physical vapor deposition
methods:
The fundamental reasons why TiAlN coatings outperform pure TiN coatings are considered to be:
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
or magnetron sputtering
.
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 depositionhave been used 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:
One commercial coating type used to improved the wear resistance of tungsten carbide tools is the AlTiN-Saturn from Sulzer Metaplas.
The coatings are sometimes doped with at least of one the elements carbon
, silicon
, boron
, oxygen
or yttrium
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
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 hardness and outstanding high temperature workability.
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
and nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
. Four important compositions (metal content 100 at.%) are deposited in industrial scale by physical vapor deposition
Physical vapor deposition
Physical vapor deposition is a variety of vacuum deposition and is a general term used to describe any of a variety of methods to deposit thin films by the condensation of a vaporized form of the desired film material onto various workpiece surfaces...
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 Sulzer Metaplas), 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 Sulzer Metaplas) group J. Vetter ca. 1996).
The fundamental reasons why TiAlN coatings outperform pure 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
Cathodic Arc Deposition
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 condenses on a substrate, forming a thin film...
or magnetron sputtering
Sputtering
Sputtering is a process whereby atoms are ejected from a solid target material due to bombardment of the target by energetic particles. It is commonly used for thin-film deposition, etching and analytical techniques .-Physics of sputtering:...
.
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 depositionhave been used 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 2600 to 3300 HV.
- Phase stability ca. 850 °C, start of decomposition to AlN+TiN.
- Intense oxidation starts at about 800 °C (ca. 300 °C higher than for TiN).
- Lower electrical and thermal conductivity than TiNTinTin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
. - Typical coating thickness ca. (1 to 7) µm.
One commercial coating type used to improved the wear resistance of tungsten carbide tools is the AlTiN-Saturn from Sulzer Metaplas.
The coatings are sometimes doped with at least of one the elements carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
, silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
, oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
or yttrium
Yttrium
Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...
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
A nanocomposite is as a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers , or structures having nano-scale repeat distances between the different phases that make up the material...
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 hardness and outstanding high temperature workability.