A study on the effect of micro and nano-debris impact on aerospace thermal barrier coating at high temperature
- Paper number
IAC-06-C2.P.1.09
- Author
Mrs. Barbara Codan, DMNR, Italy
- Coauthor
Prof. Valter Sergo, Italy
- Coauthor
Dr. Stefano Visintin, Italy
- Year
2006
- Abstract
Thermal barrier coatings (TBCs) find large application as protection shield against high temperature for the structural components in gas turbine and aeroengine parts. Typical examples are turbine blades, combustor cans, ducting and nozzle guide vanes. TBCs allowed possible an increase of the operating temperature of the engines, and that means a higher efficiency of the system. A TBC is actually a coatings system, consisting of a thermally-insulating ceramic bonded to an oxidation-resistant metal coating, which is applied to the superalloy substrate. TBCs are characterised by very low thermal conductivity, the coating bearing a large temperature gradient when exposed to heat flow. The most commonly applied TBC material is yttria stabilized zirconia (YSZ), which exhibits high resistance to thermal shock and thermal fatigue up to 1150°C, due to its low thermal conductivity k, and its relatively high thermal expansion coefficient compared to many other ceramics. During its lifetime service, TBC are continuously exposed to erosion, deriving from impacts with dust and micro-debris. This work will present the study of the effects of artificial erosion. The analysis will be performed by impacting TBCs with different kinds of materials and different sizes ranging, from hundreds of microns to hundreds of nanometers. These materials will be accelerated to velocities of 200-400 m/s, while the TBCs will be heated up to 900-1200°C. These experimental conditions simulate the real operating condition of an aircraft turbine blade. The residual stresses will be monitored via Raman spectroscopy. With this technique, it is possible to correlate frequency shifts to mechanical stress via piezospectroscopic coefficients: this information permits to understand the mechanical alterations due to the erosion. An AFM (Atomic Force Microscope) will perform topographic analysis in order to detect cracks and, more generally, any surface modifications. The analysis will be performed first on base zirconia and then on different samples of commercial blades. Depending on our tests results, other materials could be tested such as ceramic matrix nanocomposites, polymer reinforced composite, metal matrix composite and carbon/carbon. The experimental apparatus, developed for this research, is able to accelerate micro and nanoparticles at velocity up to 400 m/s, but future developments could raise higher velocities. This enhancement could improve the apparatus versatility, also for study on micrometeorites or debris impact on the Thermal, Radiation and Impact Protective Shields (TRIPS), also with a thermal control, to reproduce the real operating conditions of the aerospace structures.
- Abstract document
- Manuscript document
IAC-06-C2.P.1.09.pdf (🔒 authorized access only).
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