Electro-composite Coating for Flexible Seals
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Solution Overview
Problem
Conventional wear-resistant coatings for compliant structural seals, such as those used in gas turbine engines, are brittle and prone to delamination due to their high hardness, leading to seal failure and increased manufacturing costs due to the need for secondary processing like mechanical polishing and masking, which also results in seal height changes and potential collapse.
Innovation Solution
An electro-composite tribological coating with a cobalt and cobalt alloy base containing fine dispersions of particles like chromium carbide and silicon carbide is deposited directly on the seal using an electrolytic bath, eliminating the need for secondary processing and providing a ductile, near-net shape coating with improved wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal spray techniques are used to apply wear-resistant coatings, then wear resistance is improved, but the coating becomes brittle and prone to delamination
Solution Approach 1:
The patent changes the deposition parameters from thermal spray (high temperature, high velocity) to electro-composite plating (electrical field, controlled deposition). This parameter change produces a coating with superior ductility while maintaining wear resistance, directly resolving the contradiction between wear resistance and brittleness
Solution Approach 2:
The patent creates a composite coating structure with a ductile metallic matrix (cobalt, nickel, or copper base) reinforced with hard ceramic particles (chromium carbide, silicon carbide, tungsten carbide). This composite structure combines the ductility of metals with the wear resistance of ceramics, resolving the contradiction between these two properties
2Reliability
If thermal spray techniques are used to apply coatings, then wear resistance is improved, but secondary processing like mechanical polishing is required
Solution Approach 1:
The electro-composite plating process inherently produces a near-net shape coating with adequate surface finish and dimensional accuracy. The coating self-regulates its deposition to provide the required surface quality, eliminating the need for secondary processing operations like mechanical polishing that are required with thermal spray coatings
3Reliability
If thermal spray techniques are used to apply coatings, then wear resistance is improved, but masking and selective coating are required
Solution Approach 1:
The electro-composite plating process enables selective coating of specific seal surfaces through local electrical contact. By applying electrical current only to the outer sealing surfaces that require wear resistance, the coating is deposited only where needed, eliminating the need for masking procedures required in thermal spray processes
4Reliability
If high hardness thermal spray coatings are applied, then wear resistance is improved, but counterfaces require additional coating and grinding
Solution Approach 1:
The patent changes the coating hardness parameter to an optimal range (40-80 HRC) rather than extreme hardness (>1000 VHN). This moderate hardness level provides sufficient wear resistance while being compatible with uncoated counterfaces, eliminating the need for additional coating and grinding operations on mating surfaces
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 electro-composite coating achieves superior wear performance with reduced manufacturing costs and labor, as it maintains seal integrity during flexing and does not require additional coating or grinding of counterfaces, while maintaining a smooth surface finish without masking, thus enhancing seal longevity and operational efficiency.
Implementation Method 1
an electrolytic bath which electrolytically codeposits a cobalt and cobalt alloy base containing a fine dispersion of particles such as, chromium carbide, silicon carbide, tungsten carbide, carbon graphite and the like
Implementation Method 2
The particles utilized for the coating are quite heavy or have densities higher than the density or specific gravity of the plating solution which tends to make them settle toward the bottom of the bath
Data Source
AI summary
An electro-composite tribological coating for coating a flexible or compliant structure, for example a structural seal, includes a cobalt and cobalt alloy base containing a fine dispersion of tribologically suitable particles such as chromium carbide (Cr3C2), silicon carbide (SiC), carbon graphite, and the like, which can be deposited directly on the outer surface of the seal as a near-net shape coating requiring little or no mechanical polishing or grinding. The coating is deposited on the seal in one embodiment by an electrolytic bath. In this manner, a near-net shape coating of a desirable thickness, for example having a thickness of about 0.005″ and a desirable surface finish can be achieved in the as-plated condition with little or no additional polishing or grinding after coating.