Oxidation behavior of an ultra-refractory ceramic matrix composite under oxyacetylene torch – COMEFai

The COMEFai project aims to understand the mechanisms of oxidation during atmospheric re-entry of composite materials with ultra-refractory ceramic matrix. Materials are used in severe environments under high flux (oxidation, matter, thermal, etc.) whether for space applications (rocket, space shuttle), or defence applications related to the deterrence policy. These materials have a complex architecture (fibrous reinforcement, embedded in a matrix with possibly a protective coating) allowing both mechanical and oxidation resistance.
The materials in this project are composites, with a fibrous reinforcement that can be continuous or discontinuous; and a matrix of ultra-refractory materials in the Hf-Si-B-C or Zr-Si-B-C system. Two matrix manufacturing methods are used: (i) filling of porosity by submicrometric powder impregnation, and densification of the material by infiltration of metal or molten alloy or, (ii) fabrication by flash sintering. The formed phases within the material are known for their extreme refractory properties: HfB2, HfC and SiC or ZrB2, ZrC and SiC. The presence of silicon carbide improves the protective role of the oxide layer growing during oxidation.
The oxidation resistance of materials is tested by means of tests in an oxyacetylene flame, varying the conditions: oxygen content, angle of contact, material flow, etc. In 2023, tests at the European Synchrotron Radiation Facility – Grenoble (ESRF, 6 shifts) and the LURE – Paris Intermediate Energy Optimized Light Source (SOLEIL, 15 shifts) will allow for in-situ tomography experiments.

The originality of the COMEFai project lies in the strategy of understanding the mechanisms of oxidation, based on these in situ characterizations through synchrotron tests. This original and unique project will make it possible to monitor in situ the progression of oxidation at more than 2000°C to highlight all oxidation mechanisms as a function of time and validate the use of these materials under extreme stress conditions. At the same time, a classification of resistance to oxidation will be established between the various chemical compositions studied.