THERMOCYCLIC BEHAVIOR OF VARIOUSLY STABILIZED EB-PVD THERMAL BARRIER COATINGS

The demand for increasing gas inlet temperatures in modern gas turbine s up to 1500 degrees C and above is the main reason for the need for m ore reliable thermal barrier coatings. New ceramics should provide hig her phase stability and better resistance against chemical attack by p ollutants in the combustion gas. Electron-beam physical vapor depositi on (EB-PVD) processed, ZrO2-based TBCs were generated on bond-coated s uperalloy directionally solidified (DS) samples. Common yttria-stabili zed zirconias of two different compositions, as well as novel stabiliz ers like CeO2 and La2O3, were investigated. A columnar structure was e stablished during high-rate deposition in all cases. Diameter, degree of ordering of the columns, and phase composition depended on stabiliz er oxide and content. The role of differences of vapor pressures is ad dressed with regard to chemical homogeneity of the coatings. The perfo rmance of the TBCs having various stabilizers was investigated in a cy clic oxidation furnace test and in a burner rig at Mach 0.3. The resul ts were correlated to the type and content of stabilizer with special emphasis on phase analyses. Evaporation of new ceramic compositions ne cessitates special precautions because the vapor pressures of the comp onents may differ too much. A new dual-source evaporation coater allow s the production of these innovative TBCs with close control of chemis try. The potential of the equipment will be discussed.