For many years, Thermal Barrier Coatings (TBCs) have been employed to protect the hot section components of gas turbines against high-temperature environments. Nowadays, they are mainly produced using either Electron Beam Physical Vapor Deposition (EB-PVD) or Atmospheric Plasma Spraying (APS). Although EB-PVD is known to coat columnar microstructure, known to be porous and strain tolerant, it is also known as complicated and costly while in APS, coatings show a lower thermal conductivity with a lamellar microstruc-ture, but is less-strain tolerant.

As promising methods that can be employed to fabricate high-performance thermal barrier coatings (TBCs) which could successfully combine cost advantages and a columnar microstructure, Suspension Plasma Spraying (SPS) or Solution Precursor Plasma Spraying (SPPS) has been the focus of attention. SPS coatings due to their special microstructures, such as uniformly distributed micropores, vertical cracks or columnar structures have shown very good thermal cycle properties. However, for now, a columnar structure has not yet been achieved by SPPS for Yttria Stabilized Zirconia (YSZ) TBCs, although the porosity achieved may be higher and subsequently lower the thermal conductivity with this technique.

The primary scope of this work was to comprehensively investigate axial plasma spraying of solution precursor derived TBCs with the ambition to explore if this approach can yield a columnar YSZ microstructure that has not been previously reported using the SPPS route.

In this study, samples have been coated with different parameters, influencing dwell time, power, enthalpy, gas flow and mixture but also stand-off distance. These combinations characterised using the usual techniques for TBCs including microstructure analysis, me-chanical properties, and both erosion and thermal cycling tests.

The outcomes of this study have showed a columnar microstructure with feature matching those of SPS-based TBCs such as porosity, column density but also mechanical properties like hardness and erosion. Finally, the lifetime of these coatings has been evaluated with thermal cycle fatigue and seems to be promising.