Development of a Low Power Plasma Reactor for the Local Deposition of YSZ Thermal Barrier Coatings at Atmospheric Pressure

Abstract

Abstract Repair methods are of great interest to the aeronautic industry, especially for turbines. Deposition techniques that can quickly and easily repair small localised areas of damage in Thermal Barrier Coatings (TBCs) on combustion chambers could be financially worthwhile. In a first approach, a Low-Power Plasma Reactor (LPPR) operating at low pressure (< 1000 Pa, 240 W) was tested to locally deposit effective Yttria partially Stabilised Zirconia (YSZ) as TBC; however, a vacuum chamber would be more difficult to implement on an industrial scale. For this reason, a new LPPR (< 1 kW) operating at atmospheric pressure with solution precursors was investigated. The precursors were injected in the plasma afterglow to be sprayed and deposited onto parts of combustion chambers. As the afterglow temperature was cooler than for most thermal spray processes, spray distance was less than 10 mm. As such, YSZ deposition could be performed locally in hard-to-reach areas. YSZ coating characteristics were studied by FTIR and SEM analyses. For example, YSZ coatings exhibited the expected stoichiometry, a precursor conversion of 98 mol%, good adherence, and a porosity evaluated at approximately 30 vol%. In addition, YSZ coating thickness could be greater than 200 μm.