Columnar Suspension Plasma Spray Thermal Barrier Coatings: Influence of Suspension Properties and Bond Coat Preparation

Suspension plasma spray (SPS) is able to deposit columnar thermal barrier coatings (TBC) with enhanced strain tolerance and thermal properties relative to conventional air plasma spray (APS) processing. Columnar coatings require selection of correct processing parameters as well as suspension parameters in order to produce appropriate microstructures. Research work presently focuses on the correct balance of coating features for optimal coating performance.  

This study presents the influences of suspension parameters on microstructure and thermo-mechanical properties of SPS coatings. Suspensions were sprayed onto superalloy substrates coated with HVAF sprayed bond coats. Coating thermal conductivity was characterized together with pore size distribution. In parallel, the influence of bond coat preparation on SPS coating microstructure and lifetime in thermo-cyclic fatigue was evaluated. The overall performance of SPS TBC’s was favorable compared to classical techniques and there are indications of future routes to coating performance improvement.