Burner Rig for Small Particle Erosion Testing of Thermal Barrier Coatings

Abstract

Abstract The development of a high-temperature laboratory test to evaluate the erosion resistance of new turbine-blade thermal barrier coatings (TBC) for aircraft gas turbine engines is described. The focus is on improvements to a previously reported design, specifically: (1) larger duct and nozzle diameters leading to a larger and more uniform wear pattern; (2) incorporation of a new auger-style feeder for precise feeding of fine particles at low flow rates; (3) an aperture after the duct to limit the erosive damage at the edges of button specimens; (4) bag filters for particle feed rate measurements. The results of both extensive computational fluid dynamics (CFD) modeling and experiments concentrating on laboratory specimens fabricated from turbine-blade superalloys were used to demonstrate the validity of the test results to meaningfully evaluate the performance of new coating compositions in representative erosive environments, and to help understand damage mechanisms under such conditions. Two specimen geometries were tested in the improved rig using Mach 0.5 jets: “teardrop” burner bar and button specimens. Both types of specimens had electron beam–physical vapor deposition (EB-PVD) prepared ceramic layers of either ZrO2-Y2O3 (7YSZ) or ZrO2-Y2O3-Gd2O3-Yb2O3 (ZYGdYb) applied over PtAl bond coats using various processing parameters or interface treatments. Specimen temperatures for this study were either 980 °C (1800 °F) or 1090 °C (2000 °F).