Abstract
This article addresses the problem of gas permeability of thermal sprayed yttria-stabilized zirconia thermal barrier coatings (TBC)s. The objective of this study was to decrease the open porosity of TBCs through deposition of dense alumina ceramic on the surface of the pores. A simple infiltration technique was used, beginning with aluminum isopropoxide as sol precursor, subsequently hydrated to aluminum hydroxide sol, which decomposed at relatively low temperatures to extra-fine, readily sinterable aluminum oxide. In some experiments, the sol-gel (SG) precursor was combined with fine grains of calcined alumina, constituting high solid-yield composite sol-gel (CSG) deposits within the pores of TBCs. Sinterability in the model systems, including aluminum hydroxide sol-calcined alumina and aluminum hydroxide sol-calcined alumina-zirconia, has been studied. A number of TBC specimens were impregnated with suspensions of alumina sols and CSG. It is shown that these ceramics effectively penetrated into the pores and cracks of TBCs and reduced the coating permeability to gases. The overall reduction of porosity was however small (from ∼12 to ∼11%), preserving the strain and thermal shock tolerance of the coatings. Burner rig tests showed an increase in sealed coating lifetime under thermomechanical fatigue conditions.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
T. Troczynski, S. Cockroft, and H. Wong, Thermal Barrier Coatings for Heat Engines, Key Eng. Mater., Vol 122–124, 1996, p 451–462
S.B. Quadri, E.F. Skelton, C. Kim, and M.Z. Harford, Electron-Beam Deposition of Zirconia Films Stabilized in High Temperature Phases by Different Oxides, Surf. Coat. Technol., Vol 49, 1992, p 67–70
I. Zaplatiynsky, Performance of Lazer-Glazed Zirconia Thermal Barrier Coatings in Cyclic Oxidation and Corrosion Burner Rig Tests, Thin Solid Films, Vol 95 (No. 2), 1982, p 275–283
K.M. Jasim, R.D. Rawlings, and D.R.F. West, Pulsed Laser Processing of Thermal Barrier Coatings, J. Mater. Sci., Vol 26, 1991, p 909–916
R. Sivakumar and B.L. Mordike, Laser Melting of Plasma Sprayed Ceramic Coatings, Surf. Eng., Vol 4 (No. 2), 1988, p 127–139
N. Third, T. Troczynski, I. Smurov, M. Ignatiev, and L. Pawlowski, Physico-Chemical Treatment of Zirconia Coatings for Thermal Barriers, Thermal Spraying: Meeting the Challenges of the 21st Century, C. Coddet, ASM International, 1998, p 1337–1342
T. Sitonen, T. Konos, and P.O. Kettunen, Corrosion Properties of Stainless Steel Coatings Made by Different Methods of Thermal Spraying, Thermal Spray Industrial Applications, C.C. Berndt and S. Sampath, ASM International, 1994, p 105–110
T.E. Strangman, Thermal Barrier Coatings for Turbine Airfoils, Metallurgical and Protective Coatings, 1984, p 93–105
I. Berezin and T. Troczynski, Surface Modification of Zirconia Thermal Barrier Coatings, J. Mater. Sci. Lett., Vol 15, 1996 p 214–218
S.J. Glass and D.J. Green, Surface Modification of Ceramics by Infiltration, Adv. Ceram. Mater., Vol 2 (No. 2), 1987, p 129–131
S.J. Glass and D.J. Green, A Novel Technique for the Surface Modification of Y-TZP, Adv. Ceram., Vol 24A, 1988, p 311–318
K. Moriya, H. Tomino, Y. Kandaka, T. Hara, and A. Ohmori, Sealing of Plasma-Sprayed Ceramic Coatings by Sol-Gel Process, Thermal Spray Industrial Applications, C.C. Berndt and S. Sampath, Ed., ASM International, 1994, p 549–553
K. Moriya, W. Zhao, and A. Ohmori, Improvement of Plasma-Sprayed Ceramic Coatings Treated by Sol-Gel Process, Thermal Spray and Current Status, A. Ohmari, Ed., High Temperature Society of Japan, 1995, p 1017–1021
E.W. Washburn, The Dynamics of Capillary Flow, Phys. Rev., Second Series, Vol 27 (No. 3), 1921, p 273–284
E.O. Einset, Capillary Infiltration Rates into Porous Media with Application to Silicomp Processing, J. Am. Ceram. Soc., Vol 79 (No. 2), 1996, p 333–338
W.J. Lackey, D.P. Stinton, G.A. Cerny, and A.C. Schaffhauser, Ceramic Coatings for Advanced Heat Engine—A Review and Projection, Adv. Ceram. Mater., Vol 2 (No. 1), 1987, p 24–30
K.S. Mazdiyasni, Chemical Synthesis of Single and Mixed Phase Oxide Ceramics, Chemical Processing of Ceramics, B.I. Lee and E.J.A. Pope, Ed., American Ceramic Society, p 176–186
G. John, “Post Deposition Treatment of Thermal Sprayed Coatings,” M. Ap. Sc. thesis, UBC 1996
Q. Yang and T. Troczynski, Dispersion of Alumina and Silicon Carbide Powders in Alumina Sol, J. Am. Ceram. Soc., 1999 (in press)
Q. Yang and T. Troczynski, Composite Alumina Sol-Gel Ceramics, presented at the Symposium on Sol-Gel Processing, 100th Annual Meeting of the American Ceramic Society (Cincinnati), May 1998
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Troczynski, T., Yang, Q. & John, G. Post-deposition treatment of zirconia thermal barrier coatings using Sol-Gel alumina. J Therm Spray Tech 8, 229–234 (1999). https://doi.org/10.1361/105996399770350458
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1361/105996399770350458