Abstract: A chemical vapor infiltration method for densifying porous substrates disposed in annular stacks. The substrates to be densified (12) are loaded inside a reaction chamber (11) of an infiltration oven, being disposed in at least one annular stack (30) defining an interior passage (31) with spaces (33) being formed between the substrates. The gas admitted into the reaction chamber is channelled on leaving a preheating zone (18) towards one of the two volumes constituted by the inside and the outside of the, or each, stack of substrates, and preferably towards the smaller volume. This volume (31) is closed at its opposite end so that the gas flows from admission into the chamber to its exhaust from the chamber from the inside to the outside of the, or each, stack, or vice versa, with the gas passing through the spaces between the substrates and diffusing into them.

Abstract: The substrate (30) is placed in an enclosure (34) and is heated by direct electromagnetic coupling with an induction winding (38) to enable a temperature gradient to be established within the substrate, so that the substrate has a higher temperature in its portions remote from its exposed surfaces than in the vicinity of its exposed surfaces. A reaction gas constituting a precursor for the material to be infiltrated is admitted into the enclosure, with the formation of the material being favored in those portions of the substrate that are at higher temperature. According to the invention, the substrate is constituted by a fibrous fabric for which the ratio .rho..sub.r /.rho..sub.c of transversal electrical resistivity over longitudinal electrical resistivity is not less than 1.3, and the ratio .lambda..sub.r /.lambda..sub.c of transversal thermal conductivity over longitudinal conductivity is not less than 0.