Method of protecting a composite material part against oxidation
A method of protecting a carbon-containing composite material part against oxidation, includes applying a first coating composition in the form of an aqueous suspension on an outside surface of the part, the first coating composition including a metallic phosphate; a powder of an ingredient comprising titanium; and a powder of B 4 C; subjecting the applied first coating composition to heat treatment in order to obtain a first coating on the outside surface of the part; applying a second coating composition on the first coating composition, the second coating composition including an aqueous suspension of colloidal silica; a powder of borosilicate glass; and a powder of TiB 2 ; and subjecting the applied second coating composition to second heat treatment in order to obtain a second coating on the first coating.
1. A method of protecting a carbon-containing composite material part against oxidation, the method comprising:
applying a first coating composition in the form of an aqueous suspension on an outside surface of the part, the first coating composition comprising:
a metallic phosphate;
a powder of an ingredient comprising titanium; and
a powder of B 4 C;
subjecting the applied first coating composition to a first heat treatment in order to obtain a first coating on the outside surface of the part;
applying a second coating composition on the first coating composition, the second coating composition comprising:
an aqueous suspension of colloidal silica;
a powder of borosilicate glass; and
a powder of TiB 2 ; and
subjecting the applied second coating composition to a second heat treatment in order to obtain a second coating on the first coating,
wherein the first coating obtained on the outside surface of the part has a thickness from 40 μm to 80 μm.
2. The method according to claim 1 , wherein the ingredient comprising titanium is titanium metal.
3. The method according to claim 1 , wherein the metallic phosphate is an aluminum phosphate.
4. The method according to claim 1 , wherein the first coating composition prior to application comprises:
the metallic phosphate at a content by weight lying in the range 27% to 36%;
the powder of the ingredient comprising titanium at a content by weight lying in the range 8% to 18%; and
the powder of B 4 C at a content by weight lying in the range 11.5% to 21%.
5. The method according to claim 1 , wherein a first heat treatment temperature lying in the range 330° C. to 740° C. is imposed during the first heat treatment.
6. The method according to claim 1 , wherein the aqueous suspension of colloidal silica is basic.
7. The method according to claim 1 , wherein the second coating composition, prior to application, comprises:
the aqueous suspension of colloidal silica at a content by weight lying in the range 25% to 50%, with a content by weight of silica in the suspension lying in the range 20% to 50%;
the powder of borosilicate glass at a content by weight lying in the range 5% to 20%; and
the powder of TiB 2 at a content by weight lying in the range 30% to 60%.
8. The method according to claim 1 , wherein a second heat treatment temperature lying in the range 600° C. to 800° C. is imposed during the second heat treatment.
9. The method according to claim 1 , wherein at least one internal protection layer is formed prior to applying the first coating composition by impregnating at least a portion of the composite material part with an impregnation composition comprising a metallic phosphate.
10. The method according to claim 1 , wherein the part is a friction part.