2014-Sustainable Industrial Processing Summit
SIPS 2014 Volume 5: Composite, Ceramic, Quasi-crystals, Nanomaterials & Coatings
| Editors: | Kongoli F |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2014 |
| Pages: | 578 pages |
| ISBN: | 978-1-987820-07-2 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Densified oxide based coatings for high temperature applications
Christoph Weih1; Patrick Masset1; Gerhard Wolf1; Karl Thomas Fehr2; Sebastian Schuster1;1FRAUNHOFER UMSICHT, Sulzbach-Rosenberg, Germany (Deutschland); 2DEPT. FEHR GEO- & UMWELTWISSENSCHAFTEN, 80333, Germany (Deutschland);
Type of Paper: Regular
Id Paper: 376
Topic: 17
Abstract:
In modern processes, and at the request of a steady efficiency increase, structural materials and production tools have to face more and more severe combined thermal, chemical, mechanical loads. Therefore, the choice and production of these materials with appropriate properties become a critical criterion along the industrial production process. In addition, the extension of their service life time represents a major economic objective as it enables to decrease the material costs due to replacement, but even more important, it reduces drastically the costs for the regular installation shutdown. And finally, the required quality of the produced components can be maintained and it participates to the global improvement of the industrial productivity and competitiveness. In industrial processes the criterion for choice of materials is a balance of price and properties. The use of coating on inexpensive substrates represents an alternative. For high temperature wear and corrosion resistance the use of oxide coating is suitable. Drawbacks are: sensitivity to thermal shock, poor adhesion onto metal or alloys, high melting point, near net shape form.
In this work, a two-layer system has been coated onto the substrate. The first layer (bond coat) consists of a Ni-based alloy and depends on the substrate. The second layer (top coat) was made of ZrO2/Al2O3 or YSZ (yttrium stabilized zirconia)/Al2O3 mixtures. The ceramic-based coatings were post-treated by means of solvo-thermal process. With the increase of the temperature the residual porosity in the top coat was decreased by a factor of 50% whereas the hardness increases was by approx. 40%. This solvothermal process leads also to a significant increase of the adhesion to the bond coat. Mechanical tests of solvothermally densified coatings show improved hardness and therefore better abrasion properties as well. Corrosion tests of samples in ash-deposit at high temperature and HCl-containing atmosphere show better performance in comparison to untreated samples.