Fabrication of Thermal Barrier Coatings (TBCs) with higher lifetime and relatively cheaper processes is of particular interest for gas turbine applications. Suspension Plasma Spray (SPS) is capable of producing coatings with porous columnar structure, and it is also a much cheaper process compared to the conventionally used Electron Beam Physical Vapour Dep-osition (EB-PVD). Although TBCs fabricated using SPS have lower thermal conductivity as compared to other commonly used processes, they are still not commercialized due to their poor lifetime expectancy.

Lifetime of TBCs is highly influenced by the top coat microstructure. The objective of this work was to study and evaluate the top coat microstructure produced using axial SPS with different process parameters. 8 wt. % Yttria Stabilized Zirconia (YSZ) suspension with 25 % solid load in ethanol was used to spray the top coat. The bond coat was deposited on Has-telloy-X substrates using a NiCoCrAlY powder by High Velocity Air Fuel (HVAF) spray with same process parameters. Influence of the microstructure on lifetime of the coatings was of particular interest in this work. The coating microstructure was analysed using Scanning Electron Microscope (SEM) and it was observed that axial SPS is capable of producing TBCs with varied top coat microstructure from highly porous to densely packed columnar microstructure. The lifetime of the coatings was determined by Thermal Cyclic Fatigue (TCF) testing and Burner Rig Testing (BRT). Porosity and Thermal conductivity of the coat-ings was determined by Image Analysis and Laser Flash Analysis (LFA) respectively.

From the results obtained, it can be concluded that axial SPS could be a promising method of producing TBCs with low thermal conductivity & high lifetime for high temperature gas turbine applications.