Ni-based Superalloy Creep Strength via Re and Ru Optimization
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Solution Overview
Problem
Conventional Ni-based single crystal superalloys face challenges in achieving high creep strength in high-temperature environments while maintaining a low specific gravity, as increasing the Re composition ratio for enhanced creep strength leads to increased weight and specific gravity, affecting turbine blade performance.
Innovation Solution
A Ni-based single crystal superalloy with a composition range that includes Re exceeding 8 wt%, optimized to control the TCP phase and reduce the amount of high-specific-gravity elements like W, ensuring excellent creep strength and structural stability without increasing specific gravity, thereby enhancing the turbine blade's lightweight and high-temperature operational capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the Re composition ratio is increased to enhance creep strength, then creep strength is improved, but specific gravity increases
Solution Approach 1:
The invention changes the compositional parameters by precisely controlling the Re content to 8.1-9.9 wt% (exceeding conventional 8 wt%) while simultaneously optimizing other alloying elements (Co: 0.0-15.0 wt%, Cr: 4.1-8.0 wt%, Mo: 2.1-4.5 wt%, W: 0.0-3.9 wt%, Ta: 4.0-10.0 wt%, Al: 4.5-6.5 wt%, Ti: 0.0-1.0 wt%, Hf: 0.00-0.5 wt%, Nb: 0.0-3.0 wt%, Ru: 0.5-6.5 wt%) to achieve optimal creep strength without excessive weight gain. This parameter optimization allows the alloy to maintain high Re content for creep resistance while controlling specific gravity through balanced composition design.
Solution Approach 2:
The invention creates a composite microstructure consisting of a γ phase matrix with dispersed γ′ phase precipitates, where the γ′ phase provides precipitation strengthening. The alloy combines multiple elements with different functions: Re for solid solution strengthening and creep resistance, Al and Ti for γ′ phase formation, Cr and Mo for oxidation resistance, and Ru for TCP phase control. This multi-phase composite structure enables simultaneous achievement of high creep strength and controlled specific gravity.
2Strength
If the Re composition ratio is increased to enhance creep strength, then creep strength is improved, but TCP phase precipitation increases
Solution Approach 1:
The invention introduces Ru (0.5-6.5 wt%) as an intermediary element that specifically controls TCP phase precipitation. Ru acts as a mediator that interacts with the high Re content (8.1-9.9 wt%) to prevent harmful TCP phase formation while maintaining creep strength. The Ru element stabilizes the alloy structure at high temperatures and prevents the excess Re from combining with other elements to form TCP phases, thus resolving the contradiction between high Re content for creep resistance and TCP phase stability.
Solution Approach 2:
The invention optimizes the compositional parameters by setting Re content to 8.1-9.9 wt% (exceeding conventional levels) while simultaneously controlling Ru content at 0.5-6.5 wt% and other alloying elements within specific ranges. This coordinated parameter optimization ensures that the high Re content provides creep strength enhancement without triggering excessive TCP phase precipitation, as the balanced composition maintains structural stability in high-temperature environments.
3Strength
If heavy metal elements like W and Re are increased to enhance creep strength, then creep strength is improved, but specific gravity increases
Solution Approach 1:
The invention optimizes the parameters of heavy metal elements by setting W content to 0.0-3.9 wt% (reduced from conventional high levels) while increasing Re content to 8.1-9.9 wt%. This parameter adjustment strategy replaces some W with Re, achieving comparable or superior creep strength with potentially lower specific gravity, as Re provides efficient solid solution strengthening. The balanced composition of multiple alloying elements further optimizes the strength-to-weight ratio.
Solution Approach 2:
The invention applies local quality by assigning specific functional roles to different alloying elements at optimized concentration levels. Re (8.1-9.9 wt%) provides localized solid solution strengthening in the γ phase matrix, W (0.0-3.9 wt%) contributes to creep resistance, Ta (4.0-10.0 wt%) enhances high-temperature strength, and Ru (0.5-6.5 wt%) controls TCP phase precipitation. This localized functional distribution allows the alloy to achieve high creep strength through synergistic effects while controlling overall specific gravity through optimized element ratios.
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 maintains excellent creep strength in high-temperature environments without increasing the specific gravity, allowing for a lightweight turbine blade that can operate at higher temperatures, addressing the weight and performance issues of previous generations.
Implementation Method 1
The Ni-based single crystal superalloy acquires a metal structure suitable for strengthening through solution heat treatment at a predetermined temperature and subsequent aging heat treatment. The superalloy is called a precipitation hardened alloy which has a crystal structure with a precipitation phase (i.e., γ′ phase) dispersed and precipitated in a matrix (i.e., γ phase).
Implementation Method 2
The Ni-based single crystal superalloy acquires a metal structure suitable for strengthening through solution heat treatment at a predetermined temperature and subsequent aging heat treatment.
Data Source
AI summary
A Ni-based single crystal superalloy which has the following composition: Co: 0.0 wt % or more to 15.0 wt % or less, Cr: 4.1 to 8.0 wt %, Mo: 2.1 to 4.5 wt %, W: 0.0 to 3.9 wt %, Ta: 4.0 to 10.0 wt %, Al: 4.5 to 6.5 wt %, Ti: 0.0 to 1.0 wt %, Hf: 0.00 to 0.5 wt %, Nb: 0.0 to 3.0 wt %, Re: 8.1 to 9.9 wt % and Ru: 0.5 to 6.5 wt % with the remainder including Ni and unavoidable impurities. As a result, the Ni-based single crystal superalloy which includes more than 8 wt % of Re in the composition ratio and has excellent specific creep strength and the turbine blade incorporating the Ni-based single crystal superalloy may be made.