TRANSMISSION ELECTRON MICROSCOPY INVESTIGATIONS OF A YTTRIA-STABLILIZED ZIRCONIA ON PLATINUM ALUMINIDE BOND COAT

摘要

Cross-sectional transmission electron microscopy (TEM), including energy dispersive X-ray spectroscopy (EDS) and hollow-cone diffraction was used to characterize yttria-stabilized zirconia on platinum aluminide bond coats in the as-processed condition as well as a after oxidation for 1 and 10 hours in dry air. Columnar alpha-Al_2O_3 grains (approx 100nm) formed at the interface between the BC and YSZ in the as-processed material. These alumina grains developed into a columnar structure near the BC and equiaxial grains near the YSZ after high temperature oxidation. In the as-processed material, a thin (approx 50nm) region of interpenetrating alumina and ziroconia grains were observed between the alpha-Al_2O_3 and YSZ that developed into an interdiffusion zone of >1.2 mu m thickness after 10 hours of high temperature oxidation in dry air. No intermixing between the BC and the alumina was noted; however, Ni in YSZ was noted in the high temperature oxidized samples. Hollow cone diffraction showed that the alpha-Al_2O_3 grains and the small-grained (approx 10nm) YSZ near the alpha-Al_2O_3 were randomly oriented in the as-processed and the oxidized materials.