Nickel Braze Alloy Composition for Gas Turbine Oxide Scale Stability
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Solution Overview
Problem
Nickel braze alloys used in gas turbine engine components have reduced environmental resistance due to unstable oxide scales, which fail to provide equivalent corrosion protection compared to the nickel alloy substrates.
Innovation Solution
A blend of two alloys with specific compositions, including a high melting point first alloy and a low melting point second alloy, is used to form a stable oxide scale, enhancing environmental resistance by controlling boron content and selecting appropriate elements like chromium, aluminum, cobalt, and nickel to create a durable oxygen barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a nickel braze alloy with different composition from the substrate is used, then the brazing process can proceed (lower melting point), but the oxide scale becomes unstable and spalls, reducing corrosion protection
Solution Approach 1:
The patent modifies the chemical composition parameters of the nickel braze alloy by incorporating specific amounts of oxidation-resistant elements (chromium: 15-25 wt%, aluminum: 5-12.5 wt%, cobalt: 15-25 wt%, silicon: 0.5-6 wt%, boron: 0.05-1.0 wt%, and rare earth elements: 0.05-1.0 wt%). These parameter changes enable the formation of a stable, adherent oxide scale that provides equivalent corrosion protection to the substrate while maintaining the lower melting point necessary for brazing processability
Solution Approach 2:
The patent creates a composite alloy system by combining nickel as the base metal with multiple alloying elements that serve different functions: chromium and aluminum for oxide scale formation, cobalt for high-temperature stability, silicon and boron for grain boundary strengthening, and rare earth elements for oxidation resistance. This composite material approach achieves both brazing processability and enhanced environmental resistance
2Reliability
If the nickel braze alloy composition is optimized for stable oxide scale formation, then corrosion protection is improved, but the alloy complexity increases
Solution Approach 1:
The patent applies local quality by assigning specific functional roles to different alloying elements concentrated in specific compositional ranges. Chromium (15-25 wt%) and aluminum (5-12.5 wt%) are optimized specifically for oxide scale formation and stability, while cobalt (15-25 wt%) targets high-temperature strength, and rare earth elements (0.05-1.0 wt%) specifically enhance oxidation resistance. This localized optimization of element functions achieves superior environmental resistance with a manageable composition complexity
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 blended alloy composition achieves enhanced environmental resistance and corrosion protection by forming a stable oxide scale, improving the durability and protection of nickel braze coatings on gas turbine engine components.
Implementation Method 1
the nickel alloy of the substrate forms an oxide scale that functions as an oxygen barrier to protect the underlying nickel alloy substrate from corrosion
Data Source
AI summary
An alloy composition includes a blend of a first alloy and a second, different alloy. The blend has a combined composition including about 17.2 wt %-24.25 wt % of chromium, about 6 wt %-10.51 wt % of aluminum, about 3 wt %-23 wt % of cobalt, about 1.5 wt %-3.6 wt % of silicon, about 0.1 wt %-0.175 wt % of boron, up to about 0.163 wt % of hafnium, about 0.075 wt %-0.7 wt % of yttrium, and a balance of nickel.