Microstructural features of wear-resistant titanium nitride coatings deposited by different methods

Titanium nitride, TiN, is used as wear protective and decorative coatings i n various applications. These coatings are deposited by standard industrial methods such as chemical and physical vapor deposition (CVD and PVD, respe ctively), including magnetron sputtering or its modifications [e.g. the pla sma-enhanced magnetron sputtered deposition (PMD) method]. The coatings hav e different microstructures (size and morphology of grains, orientation, di slocation structure, residual stress, etc.) depending on the method used an d the deposition regime. The results of comparative transmission electron m icroscopy (TEM) investigations of the microstructure of thin TiN coatings d eposited by classical CVD and PVD, including PMD, are presented. The micros tructure was studied in sections perpendicular and parallel to the coating surface. The grain size was estimated from dark field images and the residu al stress was determined using the bend extinction contours in the bright f ield images. It was found that the coatings deposited by PVD and CVD method s have different grain microstructures and residual stresses. The CVD coati ngs have an equiaxed microcrystalline structure with very low levels of the local residual stress. The mean grain size is 0.4-0.6 mum. The PVD coating s (Balzers and Metaplas) have a non-equilibrium submicron grain structure w ith a high level of the local residual stress equal to 0.06-0.08E, where E is Young's modulus, and a mean grain size of 0.1-0.2 mum in the section par allel to the coating surface. The PMD coating structure is highly non-equil ibrium nanocrystalline, with a very high level of residual stress equal to 0.13E and a much finer grain size of 0.06 mum. (C) 2000 Elsevier Science B. V. All rights reserved.