Mechanical properties and damage analysis of SiCf/SiC and SiCf/SiC-EBC composites in high-temperature combustion gas environment

Abstract

Silicon carbide fiber-reinforced silicon carbide ceramic matrix composites（SiCf/SiC） used in aero-engines are damaged or even failed due to the oxidation and corrosion by high-temperature and high-speed combustion gases. In this work，the gas generation device was used to simulate the complex gas environment in the aircraft engine，and the aviation kerosene mixed with liquid oxygen fuel in a certain proportion was ignited to form a high-temperature and high-speed combustion gas to assess the material. The oxidation test for 10 h and thermal shock test for 1000 cycles in combustion gas environment at 1200 ℃ were conducted on SiCf/SiC composites respectively. And the protective effect of environmental barrier coating（EBC）on SiCf/SiC composites was investigated. Uniaxial tensile tests were conducted on SiCf/SiC composites and SiCf/SiC-EBC composites after combustion gas environment assessment，and their fracture and cross-section micro-morphologies were observed by scanning electron microscopy. The results show that no significant oxidation of fibers and interphases is found in SiCf/SiC composites and SiCf/SiC-EBC composites after oxidation for 10 h in combustion gas environment，and their uniaxial tensile strength decreases by less than 2%. After 1000 thermal shock cycles in combustion gas environment，multiple micro-cracks are formed and oxidative corrosion of the interfacial layer occurs inside the SiCf/SiC composites，and the uniaxial tensile strength decreases by 41.3%. The EBC coating can effectively protect the SiCf/SiC composites from oxidation and corrosion of high-temperature gas，and the uniaxial tensile strength of SiCf/SiC-EBC composites decreases by 16.6% after 1000 thermal shock cycles.