Mechanical properties of SiC fiber/carbon/Si‐Co matrix composites processed using film boiling and melt infiltration

Abstract This study objective is a proposal of a new lightweight and affordable structural material with heat resistance of 600–1000°C. We developed process technology and evaluated the mechanical properties of SiC fiber (Hi‐Nicalon)/Si‐CoSi 2 matrix composites. After Hi‐Nicalon fibers were woven into orthogonal three‐dimensional fabrics ( 40%), a carbon layer (FB‐C) was formed on the fiber surface using film boiling, serving as the fiber–matrix interface layer. To suppress Hi‐Nicalon strength degradation, Si‐22 at.% Co alloy with a lower melting point compared to pure Si was infiltrated at 1380°C to produce Hi‐Nicalon/FB‐C/Si‐CoSi 2 matrix composites. Dense composites with no open pores were obtained. Their bulk density was 2.7 g/cm 3 . Their mean value of four‐point bending strength was 460 MPa at room temperature and 612 MPa at 800°C in an Argon atmosphere. Fiber pullout and fiber bridging were observed clearly on the fracture surfaces. The FB‐C, with an average thickness of 4 µm, suppresses Hi‐Nicalon damage from the molten Si‐Co alloy. Furthermore, an inexpensive oxidation‐resistant coating of Si‐Co alloy dispersed with TiB 2 and SiC particles was formed on the composite surface. The four‐point bending strength in air was 424 MPa at 800°C and 539 MPa at 1200°C, demonstrating that the oxidation‐resistant coating functions effectively.