Color, structure, and properties of TiN coatings prepared by plasma enhanced chemical vapor deposition

TiN coatings were deposited onto M2 high speed steels by the plasma enhanced chemical vapor deposition process using a gas mixture of TiCl 4 , NH 3 , H 2 and Ar at various NH 3 / TiCl 4 flow rate ratios [Q( NH 3 )/Q( TiCl 4 )]. Coatings of gold color with high hardness, high elastic modulus, and low resistivity could be formed at low flow rate ratios. At higher ratios, on the other hand, brown colored coatings with considerably decreased microhardness and elastic modulus were formed. By structural and compositional analyses, as well as by observing the surface morphology of the coatings, factors which are known to affect the color of TiN coatings have been examined. Brown coatings showed a porous microstructure and possessed a great amount of oxygen compared to gold ones. However, the main factor for the color change seems to be the surface roughness of the coatings rather than the presence of oxygen or the N/Ti ratio.