Characterisation of Suspension Plasma Spray Thermal Barrier Coatings for Future Gas Turbine Application

Suspension plasma spraying offers the possibility for a new generation of thermal barrier coatings with improved thermal insulation and lifetime over existing air plasma sprayed systems currently in use. The ability of such coatings to have a high degree of porosity and yet show a column-like structure are promising characteristics for TBC´s. Presently there is a need for more coating performance data to push the performance of these new coatings further.

In this study two prospective SPS coatings are produced on either high velocity oxy-fuel or air plasma sprayed bond coats. The two cermaic systems are made with the same nano-structured suspension but with differing processing parameters. The four coating systems are compared with data for a standard air plasma sprayed TBC system.

Characterisation testing of the coating systems involved thermo-cyclic fatigue testing to assess SPS coatings behaviour with oxidation of the two bond coat systems. Thermal shock testing was performed using a burner rig to assess coating resistance to thermal shock relative to the standard coating. Thermal property evaluation both before and after a heat treatment at 1150°C was conducted using laser flash analysis. The microstructure of the coatings was investigated using SEM in the as produced state and after each test.