Elaboration of Porous Ni/8YSZ Cermet Layers by Several SPS and SPPS Routes

In this study, nickel-zirconia cermet layers are produced by solution precursor plasma spraying (SPPS) and compared with suspension plasma sprayed (SPS) coatings of similar content. Although nickel is uniformly distributed in both coatings, its presence in the suspension caused problems with the SPS process. With the SSPS process, precursor solutions are fragmented into droplets in which Ni, Zr, and Y are intimately mixed, resulting in very fine microstructure without the problems encountered with the SPS process. It was also found that plasma gas enthalpy and spray distance have predominant effects on in-flight pyrolysis of the elements, and that plasma gas mixture has an impact on porosity as well as the oxidation state of the nickel.