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Mechanical behavior in creep of thermal barriers obtained by laser deposition of zirconia ceramic stabilized with yttria and niobium in the Ti-6Al-4V alloy


The Ti-6Al-4V alloy has been used in the aerospace industry in applications that require mechanical resistance at high temperatures, low specific gravity and resistance to corrosion. However, a limiting factor of titanium alloys is oxidation due to the high affinity of titanium with oxygen. The TBC coating aims to promote protection against oxidation, corrosion and, mainly, thermal protection of metal alloys. TBC is composed of a metallic substrate, a metallic layer, a thermally grown oxide layer (TGO) and a ceramic layer. This project aims to study creep in the titanium alloy (grade 5) with TBC coating, after defining the deposition parameters of the CO2 laser coatings of the metallic layer, NiCrAlY, on Ti-6Al-4V alloy and later, of the ceramic zirconia layer with 16.0% equimolar yttria and niobium obtained by grinding in a planetary ball mill. The TGO layer will be obtained by vacuum heat treatment at 1100 ° C. The laser parameters to be defined will be the power, scanning speed and the interaction time with the sample and the thickness of the pre-deposited layers in the form of powder, and the evaluation of the sample will be by microscopy for the study of the morphology and test of nano hardness to evaluate its mechanical property. After defining deposition parameters for the CO2 laser, depositions of the TBC on titanium alloy specimens for creep tests will be performed. The laser is an agile, dynamic and assertive process, so that the definition of parameters for the deposition of the materials described above is innovative and can contribute to increasing competitiveness in the aeronautical sector by improving the TBC coating on turbine blades and, consequently, increase your efficiency. The creep test will take place in the form of constant tension at 125 MPa at temperatures of 500 ° C and 700 ° C and at temperature of 600 ° C with stresses of 125, 250 and 319 MPa. For the evaluation of the integrity of the specimens, X-ray diffraction analysis will be performed to obtain the phases obtained, scanning electron microscopy to study the morphology of the deposited layers and to obtain creep parameters to define the behavior of the alloy at high temperatures, under the protection of the thermal barrier. (AU)

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