Suspension concentration influence on SPS TBCs structure and performance

Suspension concentration influence on SPS TBCs structure and performance G. Cavazzini, A. Belletti, F. Baronio, A. Du Marteau, S. Bursich, A. Lanzi, S. Zimmermann Lincotek Surface Solutions, Rubbiano di Solignano(PR), Italy Thermal Barrier Coatings (TBCs) for aerospace and industrial gas turbines are insulating ceramic top-coats commonly deposited by atmospheric plasma spraying (APS). Among the industrial APS processes, the Suspension Plasma Spray (SPS) technology is nowadays developing as an alternative to the more expensive Electron Beam Physical Vapor Deposition (EB-PVD) for aircraft applications. The great interest in SPS coating arises from a peculiar cauliflower microstructure consisting in nano-scaled porosity and columnar structure which can enhance thermal insulation and strain tolerance under thermal cycling, thus improving coating lifetime. The SPS set-up differs substantially from the standard APS process since ethanol-based or organic suspension are the liquid carrier media for injection of nanosized particles into the plasma flow. An investigation by varying the suspension concentrations and process parameters is here presented. Different columnar microstructures produced by organic and ethanol-based suspension, on varying YSZ solid content, were analyzed by means of optical microscope. The thermo-mechanical behavior and the bond strength resistance were examined by Thermo Cycle Fatigue (TCF) and tensile adhesion (ASTM C6SS) tests.