Titanium nitride coatings: preparations, characteristics and applications

Titanium nitride (TiN) is a material with a very high melting point (2950°C), high hardness (16700 MPa) and good chemical stability (Kirk-Othmer, 1983). These caracteristics, as well as high wear resistance and golden-yellow colour, have led to an increasing interest for application of TiN in the form of thin protective and/or decorative coatings. The methods used to make coatings are physical vapour deposition (PVD) and chemical vapour deposition (CVD). The aim of this article has been to present an up to date review ofthe recent literature covering TiN preparation by both PVD and CVD method, as weIl as their characteristics and applications for various purposes. Without pretense to have covered the complete literature on the subject, it has been intended to compare parameters of the PVD and CVD preparation methods and dependance of the TiN characteristics on them. It has been equally intended to determine the range of applications and relative suitability of the methods reviewed. It has become evident that physical vapour deposition of TiN in the strict sense of the definition almost does not exist. The high melting point of TiN makes conversion of the solid compound into vapour if not impossible, then certainly very difficult and uneconomical. The modified PVD methods therefore developed for the TiN preparation, termed in this article as "reactive PVD"correspond, in fact, to the definition of the CVD. Nevertheless they were classified under PVD because they were born from the PVD methods and use the conventional PVDequipment with the necessary modifications. However, the recently developed "plasma-assisted CVD" was treated separately primarily because it makes use of the conventional PVD equipment, but with the reactive gas mixture as in the conventional CVD