Hot Corrosion-Protected Gas Turbine Disk Coatings
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Solution Overview
Problem
Gas turbine engine components, particularly high-pressure compressor and turbine disks, face significant durability risks due to hot corrosion from ingested particulate matter and SO2, which existing coatings fail to adequately address, especially in regions with high pollution and sea salt exposure, leading to concerns about low cycle fatigue and corrosion resistance.
Innovation Solution
A coating system comprising a nickel-based first layer and a chromium-based second layer, applied through electroplating, is used on a nickel-based superalloy substrate, providing a ductile interface to prevent crack propagation and offering enhanced hot corrosion resistance without a ceramic layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ceramic thermal barrier coatings are applied to disk rims and inboard portions, then thermal insulation is improved, but hot corrosion resistance deteriorates
Solution Approach 1:
The patent applies different coating compositions to different regions of the disk. The outer rim receives a first coating composition optimized for corrosion resistance, while the inboard portion receives a second coating composition optimized for thermal barrier properties. This spatial differentiation of coating properties resolves the contradiction by allowing each region to have the specific protection it needs without compromising the other region's performance.
Solution Approach 2:
The coating system is segmented into multiple distinct coating compositions applied to different zones of the disk. The first coating composition (rich in corrosion-resistant elements) and second coating composition (rich in thermal barrier elements) are applied as separate layers or regions, allowing independent optimization of corrosion and thermal protection in different areas.
2Ease of manufacture
If existing metallic coatings are applied to disk surfaces, then ease of manufacture is improved, but hot corrosion resistance deteriorates
Solution Approach 1:
The patent employs composite coating compositions that combine multiple protective elements (such as Al, Cr, Co, and rare earth elements) in specific ratios. These composite coatings provide superior hot corrosion resistance compared to conventional single-element coatings, while maintaining compatibility with existing electroplating and thermal spray manufacturing processes.
Solution Approach 2:
The patent modifies the chemical composition parameters of the coating materials by incorporating specific ratios of corrosion-resistant elements (Al: 3-15%, Cr: 5-20%, Co: 5-20%, and rare earth elements: 0.1-5%). These parameter changes enhance hot corrosion resistance while maintaining manufacturability through conventional coating application methods.
3Object-affected harmful factors
If coating thickness is increased to improve corrosion protection, then hot corrosion resistance is improved, but low cycle fatigue deteriorates
Solution Approach 1:
The patent applies thinner coating layers (5-20 micrometers) on the disk rim where corrosion protection is needed, while using thicker thermal barrier coatings (50-150 micrometers) on the inboard portions where thermal insulation is the primary concern. This localized thickness optimization ensures adequate corrosion protection without excessively thick coatings that would compromise fatigue performance in critical areas.
Solution Approach 2:
The composite coating composition provides enhanced corrosion resistance per unit thickness through the synergistic combination of multiple protective elements. This allows achieving the required corrosion protection with thinner coating layers, thereby minimizing the impact on the substrate's fatigue properties while still providing adequate hot corrosion resistance.
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 coating system effectively mitigates hot corrosion and reduces low cycle fatigue, ensuring the durability of gas turbine engine components by providing a robust, corrosion-resistant barrier that prevents crack propagation and maintains mechanical integrity under high-temperature conditions.
Implementation Method 1
A coating system comprising a nickel-based first layer and a chromium-based second layer, applied through electroplating
Data Source
AI summary
A coated article (22) comprises a substrate (100) and a coating system (102) atop the substrate. The coating system has a nickel-based first layer (104) and a chromium-based second layer (108) atop the first layer.