Composite Oxidation Coating with Bonding Underlayer
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Solution Overview
Problem
Existing protection methods for carbon-containing composite materials, such as carbon/carbon composite brake disks, have limited effectiveness against oxidation, especially in wet environments and at high temperatures, due to the degradation of B2O3 and consumption of TiB2 in known solutions.
Innovation Solution
A method involving a first coating composition with metallic phosphate, titanium powder, and B4C, followed by a second coating composition with colloidal silica, borosilicate glass, and TiB2, applied in a specific order and subjected to heat treatments, to create a bonding underlayer that enhances adhesion and oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single coating composition is applied to protect carbon-containing composite material parts, then the coating provides basic oxidation protection, but the protection lifetime is limited due to degradation of B2O3 and consumption of TiB2 in wet environments and at high temperatures
Solution Approach 1:
The protective coating is divided into two distinct layers: a first coating composition containing metallic phosphate, titanium powder, and B4C that forms a bonding underlayer, and a second coating composition containing colloidal silica, borosilicate glass, and TiB2 that provides oxidation protection. This segmentation allows each layer to perform its specific function optimally, with the first layer ensuring strong adhesion and the second layer providing durable oxidation resistance.
Solution Approach 2:
The invention uses composite coating compositions combining multiple materials with complementary properties. The first coating combines metallic phosphate (for bonding), titanium powder (for adhesion enhancement), and B4C (for high-temperature stability). The second coating combines colloidal silica, borosilicate glass, and TiB2 (for oxidation resistance). This composite approach creates a coating system with superior overall performance compared to single-material coatings.
2Reliability
If the coating thickness is increased to improve oxidation protection, then the anti-oxidation performance is enhanced, but the adhesion of the coating is reduced
Solution Approach 1:
The coating system is segmented into two functional layers with the first layer (metallic phosphate, titanium powder, B4C) specifically designed as a bonding underlayer that ensures strong adhesion to the substrate. The second layer provides oxidation protection. This segmentation allows the total coating thickness to be increased for better oxidation resistance while the first layer maintains strong adhesion regardless of the second layer's thickness.
Solution Approach 2:
The first coating composition acts as an intermediary bonding layer between the substrate and the second protective coating. This intermediate layer with its specific composition (metallic phosphate, titanium powder, B4C) provides strong chemical and mechanical bonding to both the substrate and the second coating, enabling the system to support increased total thickness without compromising adhesion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides improved adhesion and excellent resistance to oxidation in wet mediums and at high temperatures, significantly surpassing the performance of existing methods by maintaining the integrity of the protective coating.
Implementation Method 1
subjecting the applied first coating composition to heat treatment in order to obtain a first coating on the outside surface of the part
Implementation Method 2
subjecting the applied second coating composition to second heat treatment in order to obtain a second coating on the first coating
Implementation Method 3
In service in an oxidizing medium, TiB2 oxidizes and forms B2O3, thereby regenerating the B2O3 and conserving a borosilicate glass phase
Data Source
AI summary
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 B4C; 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 TiB2; and subjecting the applied second coating composition to second heat treatment in order to obtain a second coating on the first coating.