The influence of the yttrium content on the structure and properties of Ti1-x-y-zAlxCryYzNPVD hard coatings

Ti1-x-y-zAlxCryYzN and Ti1-x-yAlxCryN coatings have been grown in a multiple target PVD coating unit using the combined steered are evaporation/unbalanced magnetron deposition technique. Ti1-x-y-zAlxCryYzN him properties and yttrium distributions have been found to change significantly when three targets with equal yttrium content (Ti0.495Al0.495Y0.01) or one yttrium-containing target (Ti0.48Al0.48Y0.04) with two neighbouring pure Ti0.5Al0.5 targets to produce a non-homogeneous distribution were used. The structural characteristics and residual stresses present in the coatings were determined by X-ray diffraction using both Bragg-Brentano and glancing angle parallel beam (sin(2)psi, method) geometries. In all cases the state of stress was found to be compressive, with values at 1 degrees incidence angles of -6.5 GPa using a single 4 at.% yttrium containing target and -3.2 GPa using three TiAlY targets each containing 1 at.% Y. The residual stress value at 1 degrees angle of incidence for the Ti1-x-yAlxCryN film was similar to that of the homogeneously grown yttrium containing film, i.e. -3.8 GPa. The surface chemistry of the as-deposited and thermally treated films has been further analysed using high-resolution monochromatic X-ray photoelectron spectroscopy (XPS), Large area (700 mu m x 300 mu m) and small spot (55 mu m) XPS analysis was used to examine the role of low concentrations of the elements Y and Cr during the oxidation process. XPS imaging using O 1s, Ti 2p, Cr 2p and Fe 2p photoelectron peaks has been used to study the distribution of oxides formed on the surface after heat treatment. High resolution analysis of the Y 3d core level identified two chemical species for the as-deposited TiAlCrYN films at positions Y 3d 156.0 and 158.1 eV respectively, whilst only single species were identified in the oxidised film at Y 3d 158 eV. (C) 1999 Elsevier Science S.A. All rights reserved.