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

• Published in: Surface & coatings technology Vol. 412; p. 127050
• Main Authors: Rousseau, F., Guyon, C., Morvan, D., Bacos, M.-P., Lavigne, O., Rio, C., Guinard, C., Chevillard, B.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.04.2021; Elsevier BV; Elsevier
• Subjects: Aircraft engines; Combustion chambers; Cooling systems; Damaged TBC; Deposition; Dual flow; Engineering Sciences; Gas flow; Infiltration; Liquid precursors; Local repair; LPPR; Microstructure; Parameters; Plasmas; Plugging; Precursors; Repair; Thermal barrier coatings; Yttrium oxide; Zirconium dioxide; Liquid precursors; Infiltration; Dual flow; LPPR; Damaged TBC; Local repair; Low Power Plasma Reactor LPPR
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2021.127050

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. •A low-power plasma reactor was scaled-up for the local repair of damaged TBCs.•Vaporization of precursors depends on power density, spray distance and concentration.•TBC morphology is linked to the liquid state of the precursors on impact.•Deposited TBC infiltrates into rugosities and grain boundaries of the substrate.•Damaged APS TBCs were locally repaired without plugging the cooling channels.