TENSILE CREEP-BEHAVIOR OF A FIBER-REINFORCED SIC-SI3N4 COMPOSITE

The tensile creep behaviour of a SiC-fibre-Si3N4-matrix composite was investigated in air at 1350-degrees-C. The unidirectional composite, containing 30 vol % SCS-6 SiC fibres, was prepared by hot pressing at 1700-degrees-C. Creep testing was conducted at stress levels of 70, 110, 150 and 190 MPa. An apparent steady-state creep rate was observed at stress levels between 70 and 150 MPa; at 190 MPa, only tertiary creep was observed. For an applied stress of 70 MPa, the steady-state creep rate was approximately 2.5 x 10(-10) s-1 with failure times in excess of 790 h. At 150 MPa, the steady-state creep rate increased to an average of 5.6 x 10(-8) S-1 with failure times under 40 h. The creep rate of the composite is compared with published data for the steady-state creep rate of monolithic Si3N4.