Fluoride-mediated corrosion mechanism of atmospheric-plasma-sprayed yttrium–aluminium garnet ceramic coatings.

Atmospheric-plasma-sprayed yttrium–aluminium garnet coatings were exposed to Ar/O 2 /CF 4 plasma in a capacitively coupled plasma etching machine to induce fluoride-mediated corrosion and to elucidate the mechanism by which fluoride-containing plasma etched the coatings. In the first corrosion stage, the fully melted region, non-fused particles, and pore edges were etched; the etching products consisted of a series of aggregated and stacked fan-shaped particles, among which the non-fused particles exhibited the most severe etching. With prolonged etching, various coating surface regions gradually fused and smoothened, while the surface roughness decreased. Corrosion products Al 2 O 3 •AlF 3 , YOF, and YF 3 were also formed on the coating surface, and the etching product evolution looked like the fungus Ganoderma lucidum ; hence, the name 'fungal etching'. The study findings will further the development of ceramic coatings resistant to corrosion by halogen plasma for application to semi-conductor processing equipment. • APS YAG ceramic coatings were etched with Ar/CF 4 /O 2 plasma. • Etching products appeared on semi-molten particle surfaces/in pores/at FM zone edge. • Small fan-shaped etching traces evolved into large fungal-fruiting-body-type traces. • Etching products accumulated on coating surface were removed by ion bombardment. • Ion bombardment homogenised FM heights/integrated FM zones/smoothed coating surface. [ABSTRACT FROM AUTHOR]