MECHANICAL BEHAVIOR APPRAISAL OF THERMAL BARRIERS THROUGH ACOUSTIC EMISSION TECHNIQUES

Abstract

To develop more efficient turbines, it is necessary to increase the inlet temperature and / or decrease the temperature losses for these reasons it is necessary to develop materials resistant to higher temperatures and with lower heat transfer coefficients. A technological solution to this problem is the implementation and subsequent improvements of thermal barriers coating (TBC). In general, these TBCs are composed of a ceramic coating and an intermetallic layer that serves as a bond coat between the ceramic and the substrate to be protected. The Y2O3 stabilized ZrO2 (Y-TZP), is one of the ceramics used as TBC. However, the thermomechanical fatigue to which these barriers are subjected causes them to deteriorate, forming cracks and / or delaminations. One way to counteract this effect is the addition of an agent that allows self-healing, that is, as a crack in the barrier occurs, at the same time, the recovery of this defect is generated as a result of temperature, diffusion and / or self-healing reaction. The aim of this work is the study by acoustic emission AE of the mechanical behavior of the TBCs with the addition of SiC in the suspension of Y-TZP / Al2O3. In the same way, a microstructural analysis and a finite elements model was carried out in order to compare results. The coatings were made by Suspension Plasma Spray (SPS) on metal plates of 70x10x2 mm, an intermetallic was deposited as a bond coating and finally a coating of Y-TZP / Al2O3 with and without 15% wt SiC. The AE becomes a fundamental tool in the study of the mechanical behavior of thermal barriers. The use of wavelet transforms streamlines the study and analysis of recorded sound spectra. The cracks generation arises at very low stress levels.