Nickel-Cobalt Protective Layer Resists Embrittlement
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Solution Overview
Problem
Existing protective layers for metal components in gas turbines face challenges in maintaining high-temperature corrosion and oxidation resistance while avoiding mechanical failure due to reduced ductility from increased aluminum and chromium content.
Innovation Solution
A protective layer composed of nickel, cobalt, chromium, aluminum, and rare earth elements, with carefully optimized proportions to enhance high-temperature resistance and mechanical properties, preventing brittle phase formation and embrittlement, applied via plasma spraying or other methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the proportions of aluminum and chromium are increased to improve oxidation and corrosion resistance, then the resistance of the protective layer against oxidation and corrosion is improved, but the ductility of the protective layer deteriorates leading to mechanical failure and crack formation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the protective layer. Specifically, it limits aluminum content to 5-15 wt% and chromium to 15-30 wt%, while adding rare earth elements (0.1-5 wt%) and titanium (0.1-5 wt%). This parameter optimization resolves the contradiction by achieving sufficient oxidation/corrosion resistance without excessive aluminum and chromium that would cause brittleness
Solution Approach 2:
The patent creates a composite protective layer system consisting of multiple elements working together: base metals (nickel, cobalt, iron), oxidation-resistant elements (aluminum, chromium), rare earth elements (yttrium, lanthanum, cerium), and titanium. This composite structure achieves both high oxidation/corrosion resistance and maintained ductility through synergistic effects of the different elements
2Productivity
If the intake temperatures are increased to improve thermodynamic efficiency, then the efficiency of the gas turbine is improved, but the mechanical properties of the protective layer deteriorate due to thermal loading
Solution Approach 1:
The patent changes the thermal parameter capability by optimizing the protective layer composition to withstand higher temperatures. The specific composition (5-15% Al, 15-30% Cr, rare earth elements, titanium) enables the protective layer to maintain its mechanical properties at elevated intake temperatures up to 1100°C or more, thus supporting higher thermodynamic efficiency without sacrificing reliability
Solution Approach 2:
The protective layer acts as an intermediary between the base material and the high-temperature oxidizing environment. The optimized composition creates a stable protective oxide scale that mediates the thermal and chemical stresses, allowing the underlying material to operate at higher temperatures while maintaining mechanical integrity
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 a durable, ductile protective layer that effectively resists corrosion and oxidation at high temperatures, extending operational life and preventing mechanical failure in gas turbines, even at elevated intake temperatures.
Implementation Method 1
protective layer for protecting a component against corrosion and/or oxidation, in particular at high temperatures
Implementation Method 2
applied via plasma spraying or other methods
Data Source
AI summary
Known protective layers having a high Cr content and additionally a silicon form brittle phases which additionally become brittle under the influence of carbon during use. The protective layer hereof has a composition 22% to 24% cobalt (Co), 10.5% to 11.5% aluminum (AI), 0.2% to 0.4% yttrium (Y) and/or at least one equivalent metal from the group comprising scandium and the rare earth elements, 14% to 16% chrome (Cr), optionally 0.3% to 0.9% tantalum, the remainder nickel (Ni).