Hardness Evaluation of Nanolayered PVD Coatings Using Nanoindentation

摘要

The goal of the present work is to study the mechanical and structural properties of ZrO₂ /Al₂O₃ nanolaminated coatings and to relate them with the nanolayered structure. ZrO₂ /Al₂O₃ coatings have been grown with a nanolayered structure with 3/3.5, 6/7 and 12/14 nanometers of each layer (and with the same total thickness of 2.44 μm) using DC reactive magnetron sputtering. As substrates we have used high temperature Ni-based alloys, namely Hastelloy X. These kinds of coatings will be promissory in many technological applications where the corrosion protection combined with the wear resistance and the hard properties are required at high temperatures. Structural properties have been characterized by X-Ray Diffraction (XRD) before and after heat treatment Nanoindentation using a Berkovich indenter in a load range from 5 mN to 120 mN was used in order to calculate the hardness and Young's modulus for the as-sputtered and heat treated coating systems. The results revealed that the hardness is almost the same for the different coatings architecture for the as-sputtered coated condition. However, after heat treatment hardness increases for all coatings and reaches 24 GPa for the ZrO₂ /Al₂O₃ nanolaminated coatings prepared with 12/14 nm thickness of each layer. A detailed description of the results and their discussion will be presented in the paper.