Development of EB-PVD gradient thermal barrier coatings and their thermal-fatigue behaviors

A new type thermal barrier coating was produced by the continuous evaporation and deposition of the mixture source of Al+Al₂O₃+ZrO₂ with certain fraction ratio onto Ni-based superalloy by means of EB-PVD. The result obtained by SEM with EDS shows that the microstructure of the coating transfers gradually from metallic bond coat to ceramic top-coat and the composition distribution in the coating also changes continuously. The fundamental structure of the coating is NiCoCrAlY/ Ni₃Al/ Ni₃Al+Al₂O₃/ Al₂O₃/ Al₂O₃+ ZrO₂/ ZrO₂. The gradient thermal barrier coating has a better resistance to high temperature oxidation at 1050 °C than conventional two-layered coating. Subjected to 300 thermal cycling tests performed at 1050 °C for 30 min and forced air cooling to room temperature, the coating did not failed and exhibits good resistance to thermal shock.