Comparative investigation of TiAlC(N), TiCrAlC(N), and CrAlC(N) coatings deposited by sputtering of MAX-phase Ti2-xCrxAlC targets

A comparative investigation of the structure and properties of TiAlC(N), TiCrAlC(N), and CrAlC(N) coatings deposited by sputtering of MAX-phase Ti2-xCrxAlC targets (where x = 0, 0.5,13, and 2) in an Ar atmosphere or in a gaseous mixture of Ar + N-2 is presented. The coatings were characterized in terms of their structure, elemental and phase composition, hardness, elastic modulus, elastic recovery, thermal stability, friction coefficient, wear rate, corrosion, and high-temperature oxidation resistance. The structure of the coatings was studied by means of X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, glow discharge optical emission spectroscopy, electron energy loss spectroscopy, and Raman spectroscopy. To evaluate the thermal stability and oxidation resistance, the coatings were annealed either in vacuum or in air at temperatures 600-1200 degrees C. The results obtained show that the TiAlCN coatings possess high hardness of 32-35 GPa, low friction coefficient against WC-Co well below 0.25, high thermal stability up to 1200 degrees C, and superior performance in dry milling tests against high Cr steel. Meanwhile, the coatings with high Cr content demonstrated improved oxidation resistance up to 1000 degrees C and superior electrochemical behavior, but their mechanical and tribological properties were deteriorated. (C) 2009 Elsevier B.V. All rights reserved.