Bi- or tri- layer anti-oxidation system for carbon composite brakes

Abstract

Coated article, e.g., a brake disc, comprising a carbon-carbon composite component or a carbon-carbon-silicon carbide component coated at least with a phosphorus-containing antioxidant undercoating, the undercoating being covered by a silicon carbide particle-containing overcoating of alkali or alkaline earth metal silicate, pH modifier, and silicon carbide particles. Also, method of protecting a carbon-carbon composite brake disc or a carbon-carbon-silicon carbide composite brake disc against oxidation, by: coating the composite brake disc with a first phosphoric acid-based penetrant system; curing the penetrant coating at a temperature of 200° C. or above to form a first coating on the composite brake disc; applying the ceramic coating composition of claim 1 over the first coating and curing the ceramic coating at a temperature below 200° C. to form a second coating on the composite brake disc; and optionally coating the coated composite brake disc so obtained with a second phosphoric acid-based penetrant system; and curing the penetrant coating at a temperature of 200° C. or above to form a third coating on the composite brake disc.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood by reference to the detailed description given hereinbelow and the accompanying drawings. The drawings are not to scale, and are given by way of illustration only. They do not in any way limit the present invention.

FIG. 1 is a schematic view of a carbon-carbon composite substrate having a bi-layer coating system formed in accordance with the present invention.

FIG. 2 is a schematic view of a carbon-carbon composite substrate having a tri-layer coating system formed in accordance with the present invention.

Claims

1. A ceramic coating composition comprising 10-30 weight-% particulate silicon carbide, 60-80 weight-% water-miscible silicate binder component, and up to 20 weight-% pH modifier.

2. The ceramic coating composition of claim 1, wherein the particulate silicon carbide is submicron-size silicon carbide particles.

3. A coated article comprising a carbon-carbon composite component or a carbon-carbon-silicon carbide component, said component being covered by a phosphorus-containing antioxidant undercoating having a thickness of approximately 1-10 mil, said undercoating being covered bya silicon carbide particle-containing overcoating having a thickness of approximately 1-10 mil, said overcoating made from 60-80 wt-% water-miscible silicate-based binder solution, up to 20 wt-% alkali metal hydroxide, and 10-30 wt-% silicon carbide particles.

4. The coated article of claim 3, wherein the silicon carbide particles have particle sizes ranging from 0.05 to 0.5 microns.

5. The coated article of claim 3, wherein the silicon carbide particles have a particle size of 325 mesh.

6. The coated article of claim 3, configured as an aircraft landing system brake disc.

7. The coated article of claim 3, wherein said silicon carbide particle-containing overcoating comprises 65-75 wt-% alkali metal silicate, 5-15 wt-% alkali metal hydroxide, and 15-25 wt-% silicon carbide particles.

8. The coated article of claim 3, wherein said silicon carbide particle-containing overcoating comprises, on a solids basis, about 70 wt-% alkali metal silicate, about 10 wt-% alkali metal hydroxide, and about 20 wt-% silicon carbide particles having an average particle size of 0.1-0.2 microns.

9. The coated article of claim 3, wherein said phosphorus-containing antioxidant undercoating is formed from a penetrant salt solution containing from 5-80 wt % H20, 10-70 wt % H3PO4, up to 25 wt % alkali metal mono-, di-, or tri-basic phosphate, up to 2 wt % B2O3, and at least one of MnHPO4.1.6H2O, AlPO4, and Zn3(PO4)2, in weight-percentages up to 25 wt-%, 30 wt-%, and 10 wt-%, respectively.

10. The coated article of claim 3, wherein the undercoating is annealed to the carbon composite at a temperature in the range of 250-900° C.

11. The coated article of claim 3, wherein the silicon carbide particle-containing overcoating is dried onto the undercoating at ambient temperature for at least one hour.

12. A method of protecting a carbon-carbon composite brake disc or a carbon-carbon-silicon carbide composite brake disc against oxidation, which method comprises the steps of: coating the composite brake disc with a first phosphoric acid-based penetrant system;curing the penetrant coating at a temperature of 200° C. or above to form a first coating on the composite brake disc;applying the ceramic coating composition of claim 1 over the first coating and curing the ceramic coating at a temperature below 200° C. to form a second coating on the composite brake disc; and optionallycoating the coated composite brake disc so obtained with a second phosphoric acid-based penetrant system; andcuring the penetrant coating at a temperature of 200° C. or above to form a third coating on the composite brake disc.