Low Density Nickel-Based Superalloy for High Temperature Strength
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Solution Overview
Problem
Nickel-based superalloys used in turbomachinery face challenges in achieving improved mechanical strength, creep resistance, corrosion resistance, oxidation resistance, and reduced density, particularly at high temperatures, while also being susceptible to casting defects and microstructural instability.
Innovation Solution
A nickel-based superalloy composition with specific weight percentages of aluminum, cobalt, chromium, hafnium, molybdenum, rhenium, tantalum, titanium, tungsten, and silicon, optimized to enhance microstructural stability, creep resistance, and environmental resistance, with a directional solidification process for manufacturing turbomachinery parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional nickel-based superalloy compositions are used to achieve high-temperature performance, then creep resistance and oxidation resistance are maintained, but mechanical strength is insufficient and density is high
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ranges of multiple alloying elements (Al: 6-8%, Co: 12-15%, Cr: 4-8%, Mo: 0.5-4%, Re: 3.5-6%, Ta: 4-6%, Ti: 1-3%, W: 0-2%) to optimize the balance between mechanical strength, creep resistance, and density. This compositional parameter optimization enables achieving superior mechanical properties while reducing density compared to conventional superalloys.
Solution Approach 2:
The patent utilizes composite material principles by creating a complex multi-element nickel-based superalloy system that combines γ-Ni matrix with γ′-Ni3(Al,Ti,Ta) hardening precipitates and various alloying elements (Co, Cr, Mo, Re, Ta, W) that provide synergistic effects for enhanced strength, creep resistance, and reduced density.
2Strength
If alloy composition is optimized for improved mechanical strength, then creep resistance increases, but susceptibility to casting defects increases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the composition ranges of alloying elements, particularly controlling Re (3.5-6%), Ta (4-6%), and Mo (0.5-4%) contents to achieve high creep resistance while minimizing casting defect susceptibility. The balanced composition ensures proper solidification behavior and microstructural stability.
Solution Approach 2:
The patent applies local quality principles by ensuring uniform distribution of alloying elements throughout the casting to prevent localized compositional variations that could lead to defects. The directional solidification process further ensures consistent microstructural quality throughout the component.
3Weight of moving object
If alloy composition is modified to reduce density, then mechanical strength may be compromised, but the invention achieves both reduced density and high strength
Solution Approach 1:
The patent achieves this breakthrough through parameter changes by optimizing the composition ranges of multiple elements simultaneously, particularly utilizing Co (12-15%), Re (3.5-6%), and Ta (4-6%) to provide strength enhancement while controlling overall density to below 8.4 g/cm³, thereby decoupling the traditional density-strength trade-off.
Solution Approach 2:
The patent employs composite material strategies by creating a multi-element alloy system where different elements contribute specific functions: Co and Re for strength and creep resistance, Ta and Ti for precipitation hardening, Cr for oxidation resistance, and Mo and W for solid solution strengthening, achieving superior properties with reduced density.
4Object-affected harmful factors
If conventional superalloy compositions are used, then oxidation resistance is maintained, but corrosion resistance can be improved
Solution Approach 1:
The patent applies parameter changes by optimizing Cr (4-8%) and Al (6-8%) contents to enhance corrosion resistance through improved oxide layer formation, while maintaining microstructural stability at high temperatures through the balanced composition of γ′-forming elements (Al, Ti, Ta) and γ-stabilizing elements (Co, Cr, Re).
Solution Approach 2:
The patent uses composite material principles by creating a multi-element system where Cr provides oxidation and corrosion resistance, Al forms protective oxide layers, Co enhances high-temperature strength, and Re improves creep resistance, achieving synergistic effects that simultaneously improve corrosion resistance and maintain microstructural stability.
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 improved mechanical properties, reduced density, enhanced corrosion and oxidation resistance, and reduced susceptibility to casting defects, achieving high mechanical strength and stability at temperatures between 650°C and 1200°C, with specific mechanical properties and reduced risk of 'freckle' parasitic grain formation.
Implementation Method 1
The high-temperature performance is mainly due to the microstructure of these materials, which is composed of a γ-Ni matrix of face-centered cubic (FCC) crystal structure and ordered γ′-Ni3Al hardening precipitates of L12 structure.
Implementation Method 2
Some grades of nickel-based superalloys are used for the manufacture of single-crystal parts.
Data Source
AI summary
A nickel-based superalloy includes, in weight percent, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.2% hafnium, 0.5 to 4% molybdenum, 3.5 to 6% rhenium, 4 to 6% tantalum, 1 to 3% titanium, 0 to 2% tungsten, 0 to 0.1% silicon, the balance being nickel and unavoidable impurities.