Hardness and Oxidation Resistance of Ti0.33Al0.67N/CrN Nano-multilayered Superlattice Coatings

Abstract

Ti0.33Al0.67N/CrN nano-multilayers, which are known to have excellent wear resistance, were prepared using an unbalanced magnetron sputter to have various periods of 2-5 nm. Ti0.33Al0.67N had a hexagonal structure in a single layer, but converted to a cubic structure by forming a multilayer with CrN, which has a cubic structure. Thus, Ti0.33Al0.67N formed a superlattice in the multilayer. The Ti0.33Al0.67/CrN multilayer with a period of 2.5 nm greatly exceeded the hardness of the Ti0.33Al0.67N and the CrN single layer, reaching 39 GPa. According to the low angle X-ray diffraction results, the Ti0.33Al0.67N/CrN multilayer maintained its as-coated structure to a temperature as high as 700 degrees C and exhibited hardness of 30 GPa. The thickness of the oxide layer of the Ti0.33Al0.67N/CrN multilayered coating was less than one-tenth of those of the single layers. Thus, Ti0.33Al0.67N/CrN multilayered coating had hardness and oxidation resistance far superior to those of its constituent single layers.