Hard nanocomposite Ti-Si-N coatings prepared by DC reactive magnetron sputtering

Films resulting from Si additions to TiN matrix were prepared with Si conte nts in the range 0-19 at.%, using a closed field unbalanced DC magnetron sp uttering system. Transmission Electron Microscopy (TEM) analyses revealed t he nanocrystalline nature of these coatings, confirming the results of grai n size evaluation from X-ray diffraction (XRD) patterns. Nanoindentation te sts and scratch tests were carried out for the mechanical characterisation. Regarding the results, the samples show hardness values as high as 45 GPa. Best hardness values were found for Si content in the range 4-10 at.%. Alm ost all samples showed high critical loads for total adhesion failure, gene rally higher than 80 N, although the critical load for the first adhesion f ailure was found to be lower than 20 N for several samples. XRD patterns re vealed the presence of only one phase that can be assigned to a cubic B1 Na Cl structure, typical for TiN, with a lattice parameter of approximately 0. 430 nm. The preferential growth, as a function of Si content, changes from a strong (111) orientation at the lowest Si additions to a weak (200) orien tation at the highest Si content. Density values in the range 3.0-3.7 g/cm( 3) were obtained for most of the samples prepared with deposition rates bet ween 0.5 and 1.1 mum/h, although higher density values were obtained for hi gher Ti deposition rates, with maximum of approximately 4.7 g/cm(3) for the case of samples with low Si content. (C) 2000 Published by Elsevier Scienc e B.V. All rights reserved.