A B S T R A C T Aluminum alloys have favorable properties such as low density, high ductility and good machinability; but poor tribological behavior, nevertheless thin hard coatings cannot be directly applied onto their surface. In this research, physical vapor deposited Ti-Cr-N coatings were prepared at temperatures between 200 to 500 ° C in two thicknesses of 2 and 5 micrometers by cathodic arc on 6061 aluminum alloy substrate. Electroless Ni-P plating in two thicknesses of 10 and 20 micrometers and anodized layers in two thicknesses of 20 and 40 micrometers were employed as interlayers. Microstructure and mechanical properties of the coatings including roughness, adhesion, phase composition, hardness and coefficient of friction were studied. Phase compositions were identified by X-ray diffraction method. The frictional behavior of the coatings were studied using ball-on-disc tests under a normal load of 100 g. The results of this study showed that titanium-chromium nitride coatings applied to the substrate reduced friction coefficient from 0.8 to less than 0.3. Adhesion of the coatings to aluminum substrate was qualitatively evaluated by Rockwell C indentation tests. Surface hardness values were as high as 2000 (HV 0.1). Based on the experimental findings of this study, hard nitride coatings by physical vapor deposition method with the presence of an intermediate layer of electroless Ni-P of 20 µm thickness would improve load bearing and, as a result, tribological performance of aluminum alloys. Keywords: Aluminum, interlayer, nickel-phosphorous coating, nitride hard coating, adhesion, Anodizing
