Low power plasma spray assisted thermal barrier coating repair without the plugging of cooling holes

Abstract Currently operating new generation aircraft engines are equipped with multi-hole combustion chambers, coated with a thick ZrO2-4 mol% Y2O3 (YpSZ) thermal barrier coating (TBC). The local repair of such multi-hole combustors requires the development of specific deposition methods. This paper describes a modified version of a low power plasma reactor (LPPR), upgraded with two opposite gas flows to prevent cooling channel plugging. The influence of some experimental parameters (plasma power density, spray distance and precursor concentration) on the repaired TBC microstructure is examined. A short spray distance, associated with a low power density and a low concentration of nitrate precursors, led to a suitable microstructure of the deposited YpSZ. Moreover, FTIR spectroscopy and SEM-EDS analysis revealed the efficient conversion of the nitrate precursors into oxide and the good infiltration of the deposited YpSZ into the damaged area. Finally, it is shown that, once the deposition parameters have been optimized, a dual flow system effectively allows local repair to be carried out without plugging the cooling system.