Mechanical properties and tensile failure behavior of SiCnf/SiC composites with multilayer interphases

Abstract

SiC fiber-reinforced SiC ceramic matrix composites (SiCf/SiC CMCs) hold potential as thermal structural materials. In this work, SiC nanofibres were coated with multilayer interfaces by magnetron sputtering with the aim to tailor the fiber-matrix interface of SiC nanofibre reinforced SiC composites for superior mechanical properties. The influence of multilayer interface coating and sintering temperature on the density, microstructure, and mechanical properties of SiCnf/SiC CMCs fabricated via a hot-press technique employing ultra-long single-crystal SiC nanofibers as reinforcement were investigated. The composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and a universal testing machine. The prepared CMCs were toughened and strengthened by the observed fiber pull-out and bridging. The multilayered SiCnf/SiC CMCs with multiple interface coatings display an identifiable saw-tooth-like pattern in the load-displacement test, suggesting a significant improvement in the toughness of prepared materials through a laminated structure with weaker interface binding brought on by the thicker, denser coating. In comparison to the SiCnf/SiC composites without interface coating, the prepared SiCnf/SiC CMCs with PyC/SiAlC/ZrC interface layers revealed optimum flexural strength (520 ± 28.88 MPa, ↑46.5 %) and fracture toughness (9.95 ± 0.44 MPa m1/2, ↑94.7 %) after an hour of hot pressing at 1800 °C under pressure of 30 MPa. Besides an increase in relative density at high sintering temperatures (1850 °C), further grain coarsening deteriorated mechanical properties.