Tensile creep behaviour of a fibre-reinforced SiC-Si 3 N 4 composite

Abstract

The tensile creep behaviour of a SiC-fibre-Si 3 N 4 -matrix composite was investigated in air at 1350 ‡C. The unidirectional composite, containing 30 vol % SCS-6 SiC fibres, was prepared by hot pressing at 1700 ‡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 2.5×10 −10 s −1 with failure times in excess of 790 h. At 150 MPa, the steady-state creep rate increased to an average of 5.6×10 −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 Si 3 N 4 .