A comprehensive review of thermally sprayed abradable sealing coatings: Focusing on abradability
Jingqi Huang, Xueqiang Cao, Wenbo Chen, Xiaojun Guo, Min Li, Wenjun Wang, Shujuan Dong, Li Liu, Meizhu Chen
Abstract
Modern aero and stationary gas turbine engines have been designed with much higher compressor-pressure ratios and thrust-weight ratios than earlier models, and these ratios are strongly influenced by the hot-running clearances between the rotating and stationary components. The main benefit of reduction in the clearances is efficiency gains, resulting in lowered fuel consumption and polluting gas emissions, with ecological and economic advantages. However, at these undersized clearances, some rubbing interactions are unavoidable, which can be accommodated by applying Abradable Sealing Coatings (ASCs) on the stationary inner surface. This paper reviews the commercially available abradable materials for thermal spraying at various application positions and temperatures. Emphasis is placed on the abradability and wear mechanisms involved. In addition, considering the tendency of SiC/SiC ceramic matrix composites replacing superalloys as hot section components, the future prospect of ceramic abradables based on Environmental Barrier Coatings (EBCs) in turbine stages is summarized and a new concept of “self-degradable ceramics” based on the corrosive steam environment is proposed for the purpose of high-temperature filler-free abradables.