Creep properties and damage mechanisms of SiCf/BN/SiC mini-composites at 1300-1400 °C

This work investigates the creep properties and microstructure evolution of continuous silicon carbide fiber-reinforced silicon carbide mini-composites with a BN interface (SiC f /BN/SiC) at 1300∼1400 o C in air. The samples were subjected to tensile creep tests under loads of 60∼90N. Fracture and cross-sectional morphologies were observed via scanning electron microscopy. The elemental distribution was analyzed by energy dispersive spectroscopy. The microstructure was characterized using focused ion/electron beam microscopy and transmission electron microscopy. The results indicate that increasing temperature or load significantly increases the creep rate and shortens the creep rupture time. The SiC f /BN/SiC mini-composite exhibits excellent high-temperature stability, whose creep rupture time exceeds 500 h at 1400 o C/70N. The creep behaviors are closely associated with fiber microstructure stability and BN interface damage. SiC fibers undergo significant grain growth during creep. The average grain size of the fiber in the crept mini-composites increases to 1.31∼1.59 times that of the as-received. The BN interface forms circumferential cracks at 1300 o C while being healed by a borosilicate glass phase at 1350 o C and 1400 o C.