Abstract

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Title:: Study on Failure Mechanism of MoSi2 Coating under High-Temperature Oxygen-Enriched Flame Erosion

Author(s):: LUO Jingchuan1; ZHU Changfa2; LIU Kun2; WANG Yuesong3; XU Xiangyi4; YANG Guanjun1; CHEN Lin1; 1. State Key Laboratory for Mechanical Behavior of Materials, Xian Jiaotong University, Xian 710049, China 2. Xi’an Aero Engine Corporation in CASC, Xian 710065, China 3. The Second Military Representative of Equipment Department of the PLA Rocket Force Office in Xi’an, Xian 710065, China 4. The 8th Military Representative of Equipment Department of the Air Force Office in Xi’an, Xian 710065, China

Keywords:: MoSi2 coating; oxide film; grain boundary; vertical cracks; transverse spallation

Abstract:: 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 ≥1800 ℃. In order to reveal the failure mechanism of MoSi2 coatings, the oxidation behavior of coating on 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 leading 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 are: rapid oxidation and corrosion at the grain boundaries (GB) of the MoSi2 coatings 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 coating, and provides the reference for the development of ultra-high temperature and long-life MoSi2 anti-oxidation coatings for thrust chamber nozzles