Microstructure evolution of SiC/SiC composite ablated under an oxyacetylene torch

The microstructural evolution of a SiC/SiC composite subjected to oxyacetylene torch ablation at 2050 °C was systematically investigated. The ablated surface was divided into three regions: the central crater, the crater wall and edge, and the outer composite edge. The microstructure was strongly influenced by temperature, oxygen partial pressure, and thermodynamic forces from the torch flame, leading to the development of region-specific microstructures. In the central crater, the matrix was almost completely consumed, leaving behind needle-shaped SiC fibres. Along the crater wall, discrete spherical oxide droplets formed, which are suggested to form through re-oxidation and condensation of volatile SiO species under the strong shear force induced by the flame. Toward the crater edge, the oxide gradually transitioned into a more continuous film. At the edge of the composite, the oxide film showed a nonhomogeneous structure, consisting of large gas-inflated bubbles and ruptured thin-walled structures. Further at the far edge of composite, granular oxide particles were observed.