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| Abstract No.: |
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Scheduled at:
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Tuesday, June 03, 2008, Auditorium 2 11:30 AM
Gasturbines 2
Coatings for mobile and stationary turbines, protection against wear, high temperature corrosion and thermal stresses, clearance control coatings for a better efficiency
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| Title: |
Towards highly sintering resistant nanostructured ZrO2-7wt% Y2O3 coatings for TBC applications by employing differential sintering
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| Authors: |
Rogerio Lima* / National Research Council Canada, Canada
Basil Marple / National Research Council of Canada, Canada
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| Abstract: |
Research has demonstrated that nanostructured ZrO2-7-8wt% Y2O3 (YSZ) coatings exhibit enhanced resistance to thermal cycling when compared to conventional YSZ coatings. Despite these interesting results, there are still concerns in the scientific community about the stability of nanostructured YSZ coatings at high temperatures. In particular, questions have been raised about the possibility of accelerated sintering of these ultra-fine materials and the associated changes in properties that could accompany this sintering. In this work, nanostructured YSZ coatings were engineered to counteract sintering effects. To achieve this, nanostructured YSZ coatings were tailored to exhibit a bimodal microstructure formed by (i) a matrix of dense YSZ zones (produced molten YSZ particles) and (ii) large porous nanostructured YSZ zones (produced from semi-molten nanostructured YSZ particles) that were embedded in the coating microstructure during thermal spraying. These coatings were subjected to heat treatment in air at 1400oC for 1, 5 and 20 h. The superior driving force for sintering exhibited by the porous nanozones (high surface area), when compared to that of the dense zones (matrix), caused the nanozones to shrink at much faster rates than those exhibited by the denser matrix zones (i.e., differential sintering), thereby creating a significant network of voids in the coating microstructure. Due to these effects, after 20 h exposure at 1400oC, the thermal conductivity and elastic modulus values of the conventional coatings were approximately two times higher than those of the nanostructured ones.
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