A new approach to protect and extend longevity of the thermal barrier coating by an impermeable layer of silicon nitride

Abstract

AbstractA sample representation of a gas turbine engine blade, consisting of a nickel superalloy substrate with a deposited thermal barrier coating (TBC), was covered with silicon nitride, Si3N4, as an impermeable layer using plasma enhanced chemical vapor deposition (PECVD). The silicon nitride layer was used to seal the topcoat of yttria‐stabilized zirconia (YSZ) surface of the TBC to mitigate calcium–magnesium–aluminum–silicon oxide (CMAS) attack. CMAS testing was carried out on the covered and uncovered surfaces by melting a ratio of 25 mg/cm2 of CMAS powder onto the surface of each sample in a furnace at 1100°C for 1 h. The conformal surface reaction of the sealed layer confirmed no cracking or delamination at high temperatures. Scanning electron microscopy (SEM) micrographs confirmed that the surface of YSZ was successfully sealed. The new coating of silicon nitride was shown to be a viable solution and technique to significantly block CMAS infiltration in porous thermal barrier coatings.