Development of ZrO₂ and YSZ coatings deposited by PE-CVD below 800 °C for the protection of Ni alloys

One possibility to increase the safety of structural Ni alloys is the use of yttria stabilized zirconia coatings in order to avoid deleterious thermal effects on their mechanical properties and corrosion resistance above 800 °C. However, the deposition of YSZ with a fully cubic structure below 800 °C cannot be achieved by traditional processing routes. In this work, we show the deposition of ZrO₂ and Y₂O₃-stabilized ZrO₂ coatings by Plasma Enhanced Chemical Vapor Deposition (PE-CVD). To this purpose, the effect of deposition temperature (500–800 °C), plasma power (50–250 W) and precursor concentration (0.5–2 g) on the microstructure, composition and crystalline phase of ZrO₂ and YSZ coatings was studied. Contrary to previous reports, we show that it is feasible to use zirconium (IV) acetylacetonate [Zr (acac)₄] to produce nanostructured zirconia coatings with low carbon content (1.8 at.%) and metastable tetragonal phase. A fully cubic YSZ structure was achieved with the use of Y-acetylacetonate with concentrations above 12 mol% at 700 °C and obtain a columnar microstructure.