Evaluation of high-throughput columnar YSZ thermal barrier coatings deposited via axial plasma spraying of aqueous solution precursors

Yttria stabilized zirconia (YSZ) coatings with a columnar microstructure are desirable in gas turbine engine applications as they impart enhanced thermal cyclic fatigue (TCF) life to thermal barrier coatings (TBCs) to extend their durability under extreme conditions. Traditionally deposited via electron beam physical vapor deposition (EB-PVD), such columnar coatings have also been successfully deposited by suspension plasma spraying (SPS). However, the flammability of ethanol-based suspensions typically used to obtain columnar coatings by SPS has limited broader adoption of the latter. This study comprehensively investigates the recently reported use of aqueous solution precursors to deposit columnar TBCs by axial plasma spraying. One of the objectives is to establish a robust parametric window that enables the deposition of columnar TBCs via axial solution precursor plasma spraying (SPPS). The resulting coatings have been characterized via microstructural, phase (XRD, EBSD) and microhardness analysis. Furthermore, the erosion resistance and TCF life of these coatings have also been evaluated, accompanied by post-failure analysis to investigate the failure mechanisms. A comparison with the reported performance of SPS-deposited TBCs suggests that axial plasma spraying of powder-free aqueous solution precursors presents a potentially promising alternative to obtain columnar coatings with attractive throughputs for industrial applications.