SiC_f/O′-SiAlON composite: Properties and oxidation retained properties

A composite of O′-SiAlON (Si_2-xAl_xN_2-xO_1+x,with x ∼ 0.14) reinforced with 20 vol.% SiC monofilaments was fabricated by hot-pressing at 1600°C, for 2 h under 34 MPa pressure. The mechanical and interfacial properties of the composites, as-fabricated as well as post-oxidized, were investigated. The composite exhibited a significant improvement in ultimate flexure strength (640 MPa) and work of fracture (42 kJ m^-2) compared with that (350 MPa and 1.8 kJ m^-2, respectively) of the monolithic material. These mechanical properties were slightly increased after the composite was heat treated for 24 h in air at 1200 and 1300°C. However, the composite exhibited a significant degradation in ultimate strength, while the work of fracture (WOF) remained unchanged after exposure in air at temperatures beyond 1400°C. The as-fabricated composite revealed a low interfacial shear strength (6.2 MPa) and a frictional sliding stress (3.2 MPa). After the composite was oxidized at elevated temperatures, the interfacial bonding and sliding stresses were reduced to noticeable extents, resulting from the degradation of the carbon coating layer of the SiC monofilaments.