Abstract
In gas turbines and diesel engines there is a demand for Thick Thermal Barrier Coatings (TTBCs), because of the increased process combustion temperatures. Unfortunately the increased thickness of plasma sprayed TBCs normally leads to a reduced coating lifetime. So for that reason the coating structures have to be modified. When modifying the structure of TTBCs, the focus is normally set on elastic modulus reduction of the thick coating, in order 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 paper we introduced several modified zirconia based TTBC structures and their specific microstructural properties. Coating surface sealing procedures such as phosphate sealing, laser-glazing and sol-gel impregnation were studied as potential methods in increasing the hot corrosion and erosion resistance of TTBCs. Some microstructural modifications were also made by introducing segmentation cracks into the coating structures by laserglazing and by using special spraying parameters. These last two methods were studied in order to increase the strain tolerance of TTBCs. The coating microstructures were characterized by optical microscopy, SEM, TEM, EDS analysis and X-ray diffraction. The effect of sealing procedures was studied on basic thermal and mechanical properties of the coatings. In the paper it was also presented some correlations between the coating properties and microstructures, and discussed about the advantages and drawbacks of each modification procedure.
