Influence of rheological characteristics and stability of water-based YSZ suspensions on the morphology of plasma sprayed thermal barrier coatings

Suspension plasma spraying (SPS) makes it possible to deposit thermal barrier coatings (TBCs) with fine (sub-micron or nano) microstructures. The use of water-based suspensions provides a cheaper, safer and more environmentally friendly alternative than organic liquids. However, due to the physical properties of water, producing a water-based SPS coating with desirable microstructure has so far been elusive. In this study, the effects of solid load, pH and dispersant on the rheology and stability of YSZ water-based suspensions were investigated. Polyethyleneimine solution (PEI) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) were used as dispersant polymers. The stabilized suspensions were deposited by Axial III plasma spray system. The results showed that stable suspensions, by selecting the proper combination of pH and dispersant, contributed to coatings with favorite microstructural features for TBCs.