Effect of Particle Scale Effect on the Erosion Behavior of Cascaded Arc Plasma Spray-Deposited Coatings

Cascaded-anode plasma torches are now becoming the standard in plasma spraying with high throughput thanks to a more stable and longer plasma jet, as well as higher specific enthalpy. Better coating properties are then expected compared to coatings deposited with a conventional plasma torch. However, the relationships between the plasma torch operating conditions, characteristics of plasma jet, microstructure and properties of coatings have not been investigated yet. This study deals with the use of a mono-cathode cascaded-anode plasma torch for the deposition of Al2O3-TiO2 coatings on titanium substrates. The feedstock was injected in the plasma jet in the form of powders or suspensions. The first step consisted in investigating the plasma jet characteristics (gas specific enthalpy, jet velocity and length of the processing zone) and correlating them to the coating microstructure and phase composition; the second in experimentally observing growth conditions of suspension and powders coatings and correlating the particle size with the coating erosion resistance. The latter was tested by using a 10 000-impact standardized rain erosion test (PJET) and solid particle impingement tests (ASTM G76 and ASTM D968). This work is funding by the ANR, Safran, Airbus and Liebherr and performed in the frame of the FREEzING project.