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1 University of Minho - Physics Department, Campus de Azurem, 4800 Guimaraes,
Portugal
2 Institute for Superhard Materials, Department No.11,
2 Avtozavodskaya St., Kiev, 04074 Ukraine
*Corresponding author:
fax: +351-253510401, tel.: +351-253510465/400,
email: vasco@fisica.uminho.pt
| ZrO2-Al2O3 thin nanostructured coatings and stabilised ZrO2-Y2O3 coatings have been deposited by magnetron sputtering in rotating mode with two metallic targets in order to stabilise at room temperature the high temperature phases of zirconia. The structural studies were carried out using X-Ray Diffraction (XRD) analysis and for coatings with a content of 2wt% of Al2O3 the tetragonal phase of Zirconia can’t be stabilised. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to characterise the coatings morphology and microstructure. The mechanical behaviour of ZrO2-Al2O3 thin films under point loading conditions was studied by nanoindentation using Berkovich indenter with 130 nm tip radius. Low load tests were used to study the effect of the deposition parameters on the hardness and elastic modulus of coatings. The hardness of the films reaches 15.3 GPa for a ZrO2-Al2O3 nanostructured coating sputtered with -70V applied bias. High peak load tests were used to estimate the film adhesion to steel substrates and for 120mN peak load the film showed goog adhesion properties. The residual stresses were also determined using the Stoney equation and the highest compressive residual stress found was about -3 GPa corresponding to the sample with highest hardness. |
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