Study on Failure Mechanism of MoSi2 Coating Under High-Temperature Oxygen-Enriched Flame Erosion
MoSi2 can generate protective SiO2 on the surface during high temperature oxidation,which is expected to be used as a high-temperature oxidation-resistant coating on the inner surface of the thrust chamber nozzle.However,the MoSi2 coatings failed under the flame erosion at temperatures≥1800℃.In order to reveal the failure mechanism of MoSi2 coat-ings,the oxidation behavior of coating at various locations of the thrust chamber nozzle specimen after the flame erosion was clarified.The results show that the coating can be divided into five characteristic regions,namely the lead-ing edge,the throat,the transition section,the middle and the tail.Among them,the entire coating peels off at the throat,and the coating remains intact at the tail.The main failure mode of the MoSi2 coatings is:rapid oxidation and corrosion at the grain boundaries(GB)of the MoSi2 coat-ings result in the formation of penetrating GB cracks,the coalescence of penetrating GB cracks causes the connected and large-scale vertical cracks,dividing the coatings into island-shaped regions.Under the action of thermal shock,island-shaped coatings peel off.This research analyzes the erosion behavior of MoSi2 coating,and provides the reference for the development of long-life ultra-high temperature anti-oxidation MoSi2 coatings for thrust chamber nozzles.
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