Several kinds of thermal barrier coatings (TBCs) deposited by electron beam
physical vapor deposition (EB-PVD) were produced as a function of electron beam
power in order to evaluate their strain tolerance. The deposition temperatures were
changed from 1210 K to 1303 K depending on EB power. In order to evaluate strain
tolerances of the EB-PVD/TBCs, a uniaxial compressive spallation test was newly
proposed in this study. In addition, the microstructures of the layers were observed with
SEM and Young’s moduli were measured by a nanoindentation test. The strain tolerance
in as-deposited samples decreased with an increase in deposition temperature. In the
sample deposited at 1210 and 1268 K, high-temperature aging treatment at 1273 K for
10 h remarkably promoted the reduction of the strain tolerance. The growth of thermally
grown oxide (TGO) layer generated at the interface between topcoat and bondcoat
layers was the principal reason for this strain tolerance reduction. We observed
TGO-layer growth even in the as-deposited sample. Although the thickness of the initial
TGO layer in the sample deposited at high temperature was thicker, the growth rate
during aging treatment was smaller than those of the other specimens. This result
suggests that we can improve the oxidation resistance of TBC systems by controlling
the processing parameters in the EB-PVD process.
Heat Transfer in Thermal Barrier Coatings with Gradient Constituents Fabricated by Low Pressure Plasma Spraying
