Low Cost Suspension Plasma Spraying of YSZ Coatings

Suspension plasma spraying (SPS) process is showing promising improvements for the TBCs performance. This study will focus on developing a low cost suspension plasma spray system with high deposition rate of YSZ coatings. A unique twin-cathode plasma spray gun with three plasma torches; P-torch (reversed polarity: cathode nozzle and anode), and two N-torches (normal polarity: anode nozzle and cathode) was used. During operation, the electric power is supplied between P-torch anode and N-torches cathodes to maintain the plasma jet. The system requires only argon as plasma gas, since the enthalpy of plasma jet is enough high for melting ceramic powders, which makes it as cost reduction system. Moreover, the p-torch electrode is hollowed anode and therefore commercial dual tube nozzle was used for the axial feeding to increase the deposition efficiency. It was possible to fabricate 8YSZ coatings and its microstructure, porosity was controlled by adjusting the spraying parameters.