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-CoSi₂ matrix composites. After Hi-Nicalon fibers were woven into orthogonal three-dimensional fabrics ($V_f$ 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-CoSi₂ matrix composites. Dense composites with no open pores were obtained. Their bulk density was 2.7 g/cm³. 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 TiB₂ 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.