In this paper, a multicomponent hard coating system of Cr-Ti-Al-N has been studied for its structural, mechanical and tribological properties under different chemical compositions. The coatings were deposited onto AISI M42 steel plates by closed-field unbalanced magnetron sputtering ion plating (CFUBMSIP) technique in a gas mixture of Ar+N-2. Three processing steps in deposition involved were plasma ion cleaning, buffer layer deposition, and multicomponent layer deposition. During the final deposition step, nitrogen concentration was controlled at similar to 50 at.% by using the feedback control of metal plasma optical emission monitor (OEM). The metallic ratio of Cr, Ti, and Al was varied by adjusting the currents of different magnetron targets. The coatings were characterized by means of energy dispersive X-ray (EDX) analysis, X-ray photoclectron spectrometry (XPS), X-ray diffractometry (XRD), Rockwell-C indentation tester, microhardness tester, and pin-on-disc (POD) tribometer, in order to check their chemical composition, as well as to determine the structural, mechanical and tribological properties. The experimental results showed that the optimised quaternary Cr-Ti-Al-N coating performs better than the binary CrN as well as the ternary Cr-Ti-N and Cr-Al-N coatings in terms of hardness and wear resistance. The introduction of both Ti and Al elements into the CrN-based coatings enhances both of their mechanical and tribological performance. (C) 2007 Elsevier B.V. All rights reserved.