| Abstract: |
Suspension plasma spraying (SPS) of micrometric or nanometric sized particles is a versatile and emerging technology that allows manufacturing finely structured coatings. Alumina based materials possess high hardness, electrical insulation as well as chemical and thermal stability making them suitable for wear-resistant or erosion-resistant applications even in corrosive environments, for dielectric layers, for sensors? In the present work a pressurized gas delivery system feeds the slurry through a home made two-fluid atomizing nozzle to a conventional plasma torch. Alumina and alumina-zirconia coatings were manufactured using various size distributions of the feedstock materials. Depending on the atomization conditions, either a liquid jet or a spray was produced and injected into the plasma jet. Temperatures and velocities of the particles were measured with a commercial diagnostic system (Accuraspray ®) at the spraying distance as a function of the plasma operating parameters (nature and flow rates of the plasma gases, plasma power, nozzle diameter). Temperatures around 2600°C for alumina and velocities as high as 450m/s have been detected. Coatings have been produced by suspension plasma spraying and compared to conventional atmospheric plasma spraying ones. XRD analyses were performed to assess the various phases (á to â ratio for alumina, m to t ratio for YSZ, amorphous phase). Coatings with high amount of á-alumina phase have been produced. Micromechanical properties and tribological behaviour were studied for several selected coatings of alumina and alumina-YSZ. Friction coefficient as low as 0.3 have been achieved for alumina coatings with almost no wear.
This work was supported by the French National Research Agency (Agence Nationale de la Recherche) under the grant n°ANR-06-PANH-007 CERAMET.
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