Achieving high creep resistance in SiC_f/SiC composites at 1650 °C in air by engineering a PyC-iBN bilayer interphase

The demand for silicon carbide fiber-reinforced silicon carbide (SiC_f/SiC) composites with enhanced creep resistance has become increasingly critical for long-term applications exceeding 1650 °C in air. Their creep lifetime is predominantly governed by their proportional limit stress (PLS) and the intrinsic creep resistance of the SiC fibers. Herein, we report the fabrication of SiC_f/SiC composites with Cansas™ 3303 SiC fibers featuring a PyC and in-situ grown BN (PyC-iBN) bilayer interphase. A two-dimensional eight-harness satin preform was utilized. The PyC-iBN interphase (∼0.6 μm) was synthesized in situ by chlorination and carbothermal reduction methods. The resulting composite prepared by chemical vapor infiltration (CVI) exhibited an outstanding PLS of 248.66 MPa, which endowed it with superior creep resistance, demonstrated by a 100-h creep life at 1650 °C under 35 MPa in air. Fractographic analysis revealed extensive fiber pull-out, interfacial debonding, and sliding, indicating that the PyC-iBN bilayer interphase effectively facilitated load transfer and imparted remarkable toughening. This work provided a viable strategy for designing high-performance SiC_f/SiC composites for ultra-high-temperature applications.