Experimental verification of PTC diagrams for TiC and ZrC PVD coatings and determination of free carbon state by AES, XPS and HREELS methods
Abstract
Abstract Several PVD coatings based on Ti and Zr carbides and on HSS steel were investigated. The partial pressure of the active gas (N 2 , C 2 H 2 ) and substrate temperature were varied over a wide range. The PTC diagrams for prediction of coating compositions, dependent on substrate temperature and gas pressure, were calculated using the thermodynamic technique for phase equilibria based on the principle of maximum entropy in an isolated thermodynamic system. The chemical composition, and electronic and atomic structure of coatings were investigated using the AES, XPS and HREELS methods. Comparison of the calculated chemical composition of coatings with one measured by AES shows good agreement. XPS analysis of the C 1s line in carbides of Ti and Zr shows the presence of carbon in non‐stoichiometric carbides and in the free state. The fraction of bound and free carbon was measured by relation of the shifted and normal C 1s peaks. HREELS spectra near the line of elastically scattered electrons show a peak at 165 meV (1332 cm −1 in Raman spectroscopy) corresponding to sp hybridization of carbon. Copyright © 2004 John Wiley & Sons, Ltd.