Dense to Columnar Microstructure Evolution of Ba(Mg_1/3Ta_2/3)O₃ TBCs Through Tailoring of Suspension Plasma Spray Conditions

Solution precursor plasma spraying (SPPS) was used to deposit barium magnesium tantalate thermal barrier coatings on titanium alloy substrates. The suspension was axially fed into an inductively-coupled RF plasma torch with a 25-mm converging nozzle. By selecting an atomization probe with a bimodal distribution of droplet size and adjusting the precursor feed rate and spraying distance, it was possible to tune the coating microstructure from dense splat-like layers to columns with intracolumnar porosity of 4.3% and intercolumnar porosity of 10%. The deposition rate achieved is suitable for commercial use.