To form a coating for protection against oxidation at high temperature on a refractory composite material based on silicon and of niobium

摘要

The process comprises reacting a reactive gas containing silicon and oxygen with chromium present on a surface of a refractory composite material (1) to be protected to develop a composite coating in two phases, coalescing the first phase and second phase at high-temperature for forming a protective coating in which the second phase serves as a reservoir for reforming the first phase by reaction with an oxidizing gas, and reacting first and second reactant gases. The process comprises reacting a reactive gas containing silicon and oxygen with chromium present on a surface of a refractory composite material (1) to be protected to develop a composite coating in two phases, coalescing the first phase and second phase at high-temperature for forming a protective coating in which the second phase serves as a reservoir for reforming the first phase by reaction with an oxidizing gas, reacting a first reactant gas containing silicon monoxide produced from the donor cement containing silicon dioxide and silicon carbide in the form of powder and a second reactive gas containing silicon monoxide and boron monoxide produced by a second donor cement containing silicon dioxide and boron carbide in the form of powder on the composite material, forming a deposit of tin on the surface to be protected, followed by heat treatment under vacuum, forming a deposit of a precious metal consisting of platinum, palladium and gold on the surface to be protected, followed by an annealing of interdiffusion, and forming a deposit of titanium nitride on the surface to be protected. The first phase is an oxide phase made of silicon dioxide having adjustable viscoplastic characteristics and the second phase is made of silicon, chromium and oxygen. The reactive gas contains silicon monoxide and boron monoxide, and is produced in situ from a donor cement containing silicon dioxide subjected to a temperature of = 1450[deg] C. The donor cement contains a mixture of silicon dioxide and silicon carbide in powder form. The first phase made of silicon dioxide further contains flux elements of boron and/or germanium, which adjust viscoplastic characteristics of first phase according to the temperature range of service. The entire or part of chromium present on the surface to be protected is obtained by a pre-deposit that is placed on the surface to be protected to form a layer of desired thickness of 15 mu m. The pre-deposit is obtained by electrolytic deposition technique or sputtering deposition. Independent claims are included for: (1) a protective coating; and (2) a part made of a composite material.