Characterization of modified thick thermal barrier coatings |
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Authors: | Ahmaniemi S Tuominen J Vippola M Vuoristo P Mäntylä T Cernuschi F Gualco C Bonadei A Di Maggio R Ahmaniemi S |
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Affiliation: | 1.Tampere University of Technology/Institute of Materials Science, Tampere, Finland ;2.Centro Elettrotecnico Sperimentale Italiano, Segrate, Italy ;3.Ansaldo Ricerche, Genova, Italy ;4.University of Trento/Department of Materials Engineering, Trento, Italy ; |
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Abstract: | In gas turbines and diesel engines, there is a demand for thick thermal barrier coatings (TTBCs) due to the increased process
combustion temperatures. Unfortunately, the increased thickness of plasma-sprayed thermal barrier coatings (TBCs) normally
leads to a reduced coating lifetime. For that reason, the coating structures have to be modified. When modifying the structure
of TTBCs, the focus is normally on elastic modulus reduction of the thick coating to improve the coating strain tolerance.
On the other hand, coating structural modification procedures, such as sealing treatments, can be performed when increased
hot-corrosion resistance or better mechanical properties are needed. In this article, several modified zirconia-based TTBC
structures with specific microstructural properties are discussed. Coating surface sealing procedures such as phosphate sealing,
laser glazing, and sol-gel impregnation were studied as potential methods for increasing the hot-corrosion and erosion resistance
of TTBCs. Some microstructural modifications also were made by introducing segmentation cracks into the coating structures
by laser glazing and by using special spraying parameters. These last two methods were studied to increase the strain tolerance
of TTBCs. The coating microstructures were characterized by optical microscopy, a scanning electron microscopy (SEM), transmission
electron microscopy (TEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). The effect of sealing procedures
on the basic thermal and mechanical properties of the coatings was studied. In addition, some correlations between the coating
properties and microstructures are also presented, and the advantages and drawbacks of each modification procedure are discussed. |
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Keywords: | diesel engine hot corrosion laser glazing sealing thermal barrier coating |
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