Fluoride-mediated corrosion mechanism of atmospheric-plasma-sprayed yttrium–aluminium garnet ceramic coatings. Issue 13 (October 2022) - Huang, Biao
Abstract: Atmospheric-plasma-sprayed yttrium–aluminium garnet coatings were exposed to Ar/O2 /CF4 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 Al2 O3 AlF3, YOF, and YF3 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. Highlights: APS YAG ceramic coatings were etched with Ar/CF4 /O2 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.