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Thermal conductivity and phase evolution of plasma-sprayed multilayer coatings.
- Source :
- Journal of Materials Science; Jul2001, Vol. 36 Issue 14, p3511-3518, 8p
- Publication Year :
- 2001
-
Abstract
- Multilayer coatings were prepared using small-particle plasma spray to investigate the effect of interfaces on thermal conductivity and phase stability. Monolithic and multilayer alumina and yttria partially-stabilized zirconia coatings, with 0, 3, 20, and 40 interfaces in 200–380 μm thick coatings were studied. Thermal conductivity was determined for the temperature range 25 °C to 1200 °C using the laser flash method and differential scanning calorimetry. Thermal conductivity of the multilayer coatings was accurately modeled by a series heat transfer equation, indicating that interfacial resistance plays a negligible role in heat transfer in the direction perpendicular to the coating plane. Powder X-ray diffraction results indicate that identical phase transitions occur in all the coatings. Independent of coating microstructure (i.e. layer thickness), as-sprayed γ-Al<subscript>2</subscript>O<subscript>3</subscript> transforms to α-Al<subscript>2</subscript>O<subscript>3</subscript> after 100 hours at 1200°C; as-sprayed metastable t′–ZrO<subscript>2</subscript> converts to a mixture of t–ZrO<subscript>2</subscript> and c–ZrO<subscript>2</subscript> after 100 hours at 1300 °C. Thus, the results indicate that the interfaces do not aid in stabilizing the as-sprayed phases after prolonged severe heat treatments. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00222461
- Volume :
- 36
- Issue :
- 14
- Database :
- Complementary Index
- Journal :
- Journal of Materials Science
- Publication Type :
- Academic Journal
- Accession number :
- 52538450
- Full Text :
- https://doi.org/10.1023/A:1017932617123