Method for chemical infiltration in the gas phase for the densification of porous substrates with pyrolytic carbon

A chemical vapor infiltration method for densifying porous substrates with pyrolytic carbon, the method comprising the steps of:

• loading one or more porous substrates for densifying in an oven;
• admitting into the oven a reaction gas containing a pyrolytic carbon precursor reagent gas having at least one gaseous hydrocarbon CxHy in which x and y are natural integers and x is such that 1<x<6, together with a vector gas comprising at least one gas selected from methane and inert gases;
• extracting from the oven an effluent gas containing residual components of the admitted gas and reaction products, including hydrogen;
• and
• extracting from the effluent gas a gas stream containing residual pyrolytic carbon precursor reagent gas and vector gas for recycling at least a fraction of said gas stream into the reaction gas admitted into the oven;
• measuring at least the quantities of pyrolytic carbon precursor gas and of vector gas contained in said gas stream extracted from the effluent gas;
• and
• as a function of the measured quantities, controlling at least:
• the flow rate of said gas stream that is recycled into the reaction gas and that contains pyrocarbon precursor reagent gas and vector gas;
• the flow rate of precursor gas coming from an external source of pyrolytic carbon precursor gas and injected into the reaction gas;
• and the flow rate of vector gas coming from an external source of vector gas and injected into the reaction gas;
• wherein said controlling is performed in such a manner as to obtain a desired fraction of pyrolytic carbon precursor gas in the reaction gas admitted into the oven.