Composite-Coated Piston Seal for High-Temperature Wear Reduction
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Solution Overview
Problem
Piston rings in gas turbine engines experience significant wear and increased friction due to high temperatures and vibratory motion, despite using nickel-based alloys, which fail to provide adequate creep and wear resistance.
Innovation Solution
A piston seal assembly featuring a nickel-based superalloy with a coating comprising a metal alloy binder phase and a hard particle phase, specifically Cr2O3 particles, applied to the seal-counterface areas, providing enhanced wear resistance and reduced friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nickel-based superalloy is used for piston seal, then creep resistance is improved, but wear resistance deteriorates due to chromia and alumina formation on surface
Solution Approach 1:
The patent applies a composite coating system consisting of multiple layers: a bond coat layer and a top coat layer containing hard particles (such as chromium carbide, silicon carbide, or diamond) dispersed in a metal matrix. This composite structure combines the creep resistance of the nickel-based superalloy substrate with the wear resistance of the hard particle reinforcement in the coating, resolving the contradiction between creep and wear resistance.
Solution Approach 2:
The patent modifies the surface properties of the piston seal by applying a coating with controlled composition and structure. The coating parameters (hard particle type, size distribution, volume fraction, and layer structure) are optimized to achieve low friction and wear resistance while maintaining compatibility with the underlying nickel-based superalloy substrate, thereby improving wear resistance without compromising creep resistance.
2Strength
If nickel-based superalloy is used for piston seal, then high temperature strength is improved, but friction increases due to oxide formation
Solution Approach 1:
The patent employs a composite coating containing hard particles (chromium carbide, silicon carbide, or diamond) embedded in a metal matrix within a multi-layer structure. This composite material provides a low-friction surface that prevents harmful oxide formation at high temperatures, while the underlying nickel-based superalloy maintains high temperature strength. The coating acts as a protective barrier that eliminates the friction problem without sacrificing thermal mechanical performance.
Solution Approach 2:
The patent converts the harmful effect of oxide formation into a beneficial protective oxide layer on the bond coat surface. The bond coat layer is designed to form a stable, protective oxide barrier that prevents further oxidation and reduces friction, while the top coat with hard particles provides additional wear and friction protection. This approach transforms the potentially harmful oxidation process into a protective mechanism.
Data Source
AI summary
A piston seal assembly for a gas turbine engine includes a seal composed of a nickel-based superalloy; a component in contact with the seal and defining a seal-counterface; and a coating on the seal at the seal-counterface, wherein the coating is a metal alloy binder phase and a hard particle phase distributed through the binder phase.