Solid dust induced roughening and overheating of TBC-coated superalloy

Abstract

Thermal barrier coatings (TBC) on superalloy blade/vane enable an increase in turbine inlet temperature (TIT) and aero-engine efficiency. However, the deposition of dust on TBC significantly ablates superalloys and becomes a bottleneck for advanced engine development. This paper presents a comprehensive modeling approach, based on an experiment involving dust deposition on a TBC-coated substrate, aimed at understanding the fundamental cause of substrate ablation. The results show that a significant increase in surface roughness is obtained experimentally with dust accumulation. The temperature field within the TBC-substrate system is disturbed by surface roughening. Consequently, the film cooling is seriously destroyed. While the dust accumulated on the TBC surface also contributes to heat insulation by increasing the effective TBC thickness, localized overheating of the substrate occurs and then leads to ablation and premature failure of the substrate. This elucidation of the overheating mechanism could inform the development of strategies to resist dust accumulation in advanced aero engines.