Combined zirconia toughened alumina (ZTA) stacks obtained by electron beam physical vapour deposition

Ion assisted electron beam physical vapour deposition (EB-PVD) technique was used for three zirconia toughened alumina (ZTA) batches containing 15, 25, 35, mole% ZrO2 and c-zirconia ceramic multilayer deposition on 617-Ni based alloy substrate. The ceramic batches were prepared via sol-gel technique. The thickness of the coated layers was found to be 0.66 μm for ZTA layers and 0.65 μm for c-zirconia layer. Evaluation of the microstructure of the samples coated with c-zirconia on the top of different ZTA coats reveals three different regions. First region indicates c-ZrO2 coat, second region exhibits ZTA layers, while third is the metallic substrate. The top coat microstructure can be divided into two zones. The inner zone (ZTA zone), which is the early part of multiple nucleation and subsequent growth of the columnar microstructure. The outer zone (c-ZrO2) which is crystallographically perfect columnar YSZ coatings produced by EB-PVD.