High-temperature chemical stability of plasma-sprayed Ca_0.5Sr_0.5Zr₄P₆O₂₄ coatings on nicalon/SiC ceramic matrix composite and Ni-based superalloy substrates

The potential application of Ca_0.5Sr_0.5Zr₄P₆O₂₄ (CS50) as a corrosion-resistant coating material for Si-based ceramics and as a thermal barrier coating material for Ni-based superalloys was explored. A ∼200 μm thick CS50 coating was prepared by air plasma spray with commercially available powder. A Nicalon/SiC ceramic matrix composite and a Ni-based superalloy coated with a ∼200 μm thick metallic bond coat layer were used as substrate materials. Both the powder and coating contained ZrP₂O₇ as an impurity phase, and the coating was highly porous as-deposited. The coating deposited on the Nicalon/SiC substrate was chemically stable upon exposure to air and Na₂SO₄/O₂ atmospheres at 1000°C for 100 h. In contrast, the coating sprayed onto the superalloy substrate significantly reacted with the bond coat surface after similar oxidation in air.