Method for making a part of composite material with ceramic matrix and resulting part

1. A method of fabricating a composite material part comprising fiber reinforcement densified by a ceramic matrix, the method comprising:

using chemical vapor infiltration to form an interphase coating on the fibers to be used for constituting the fiber reinforcement without the fibers being held in shape by a tooling, the interphase coating comprising at least an inner layer in contact with the fibers for providing embrittlement relief to the composite material, and an outer layer for bonding with the ceramic matrix and the interphase coating having a thickness of less than 100 nanometers;

after forming the interphase coating, shaping a fiber preform to constitute the fiber reinforcement of the composite material part, the fiber preform being formed of said fibers provided with the interphase coating, and holding the fiber preform by means of a tooling to keep its shape;

consolidating the preform while kept in its shape by means of said tooling by partial densification using a consolidating phase of ceramic matrix bonding the fibers to one another to obtain a consolidated preform able to conserve its shape on its own without help from tooling, consolidation being performed by impregnating the fiber preform with a liquid composition containing a precursor for the material of the ceramic matrix consolidating phase, and transforming the precursor into ceramic; and

continuing densification of the consolidated preform by an additional ceramic matrix phase.

2. A method according to claim 1 , in which the fiber preform is made by shaping a fiber texture, the method being characterized in that the interphase coating is formed on the fibers of the fiber texture before making the preform.

3. A method according to claim 2 , in which the interphase coating is formed on the fibers constituting the fiber texture before the texture is formed.

4. A method according to claim 1 , wherein the inner layer of the interphase coating is made of a material selected from pyrolytic carbon, boron nitride BN, and boron-doped carbon BC.

5. A method according to claim 1 , wherein the outer layer of the interphase coating is made of a ceramic material similar to that of the matrix consolidating phase.

6. A method according to claim 1 , in which consolidating the preform includes impregnation by a liquid composition containing a resin that is a precursor of the ceramic material of the matrix consolidating phase.

7. A method according to claim 1 , in which the densification of the preform consolidated by an additional ceramic matrix phase is performed by chemical vapor infiltration.