Titanium Aluminium Nitride

- Jul 13, 2018-

Titanium aluminium nitride (TiAlN) or aluminium titanium nitride (AlTiN; for aluminium contents higher than 50%) stands for a group of metastable hard coatings consisting of the metallic elements aluminium and titanium, and nitrogen. Four important compositions (metal content 100 at.%) are deposited in industrial scale by physical vapor deposition 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 Titanium nitride (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