Abstract
Commercially available mullite (3Al2O3·2SiO2) powders containing oxides of calcium and iron as impurities, have been made suitable for plasma spraying by using an organic binder. Stainless steel substrates covered with Ni-22Cr-10Al-1.0Y bond coat were spray coated with mullite. The 425 µm thick coatings were subjected to thermal shock cycling under burner rig conditions between 1000 and 1200 °C and less than 200 °C with holding times of 1, 5, and 30 min. While the coatings withstood as high as 1000 shock cycles without failure between 1000 and 200 °C, spallation occurred early at 120 cycles when shocked from 1200 °C. The coatings appeared to go through a process of self erosion at high temperatures resulting in loss of material. Also observed were changes attributable to melting of the silicate grains, which smooth down the surface. Oxidation of the bond coat did not appear to influence the failure. These observations were supported by detailed scanning electron microscopy and quantitative chemical composition analysis, differential thermal analysis, and surface roughness measurements.
Similar content being viewed by others
References
N. Carlson and B.L. Stoner, “Thermal Barrier Coating on High Temperature Industrial Gas Turbine Engines,” NASA CR-135147, Feb 1977
R.A. Miller and C.C. Berndt, Performance of Thermal Barrier Coatings in High Heat Flux Environments, Thin Solid Films, Vol 119, 1984, p 195–202
J.T. DeMasi-Marcin and D.K. Gupta, Protective Coatings in the Gas Turbine Engine, Surf. Coat. Technol., Vol 68/69, 1994, p 1–9
A. Maricocchi, A. Bartz, and D. Wortman, PVD Experience on GE Aircraft Engine, J. Therm. Spray Technol., Vol 6 (No. 2), 1997, p 193–198
A. Bennett, Properties of Thermal Barrier Coatings, Mater. Sci. Technol., Vol 2, March 1986, p 257–261
P. Vincenzini, Zirconia Thermal Barrier Coatings for Engine Applications, Ind. Ceram., Vol 10 (No. 3), 1990, p 113–126
P. Ramaswamy, S. Seetharamu, K.B.R. Varma, and K.J. Rao, Al2O3-ZrO2 Composite Coatings For Thermal Barrier Applications, Compos. Sci. Technol., Vol 57, 1997, p 81–89
K.N. Lee, R.A. Miller, and N.S. Jacobson, New Generation of Plasma Sprayed Mullite Coatings on Silicon Carbide, J. Am. Ceram. Soc., Vol 78 (No. 3), 1995, p 705–710
D.P. Butt, J.J. Mecholsky, Jr., M. Van Roode, and J.R. Price, Effects of Plasma Sprayed Distribution of Silicon Carbide Materials, J. Am. Ceram. Soc., Vol 73 (No. 9), 1996, p 2690–2696
K.N. Lee and R.A. Miller, Oxidation Behavior of Mullite-Coated SiC and SiC/SiC Composites under Thermal Cycling between Room Temperature and 1200 °C–1400 °C, J. Am. Ceram. Soc., Vol 79 (No. 3), 1996, p 620–626
K. Kokini, Y.R. Takeuchi, and B.D. Choules, Surface Thermal Cracking of Thermal Barrier Coatings Owing to Stress Relaxation: Zirconia vs. Mullite, Surf. Coat. Technol., Vol 82, 1996, p 77–82
P. Ramaswamy, S. Seetharamu, K.B.R. Varma, and K.J. Rao, A Simple Method for the Preparation of Plasma Sprayable Powders Based on ZrO2, J. Mater. Sci., Vol 31, 1996, p 6325–6332
T. Yonushonis, “Ceramic Thermal Barrier Coating for Rapid Thermal Cycling Applications,” U.S. Patent No. 5,320,909, 14 June 1994
P. Ramaswamy, S. Seetharamu, K.B.R. Varma, and K.J. Rao, Evaluation of CaO-CeO2-partially Stabilized Zirconia Thermal Barrier Coatings, accepted for print in Ceram. Int.
H. Schneider, K. Okada, and J. Pask, Mullite and Mullite Ceramics, Chapter 3, John Wiley & Sons, p 83–104
C.N.R. Rao and K.J. Rao, Phase Transitions in Solids, Chapter 1, McGraw-Hill International, 1979
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Ramaswamy, P., Seetharamu, S., Rao, K.J. et al. Thermal shock characteristics of plasma sprayed mullite coatings. J Therm Spray Tech 7, 497–504 (1998). https://doi.org/10.1361/105996398770350710
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1361/105996398770350710