Ni-based Casting Superalloy Composition for High-Temperature Strength
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Solution Overview
Problem
Current Ni-based superalloys for high-temperature components, such as gas turbine blades, face challenges in achieving a balance between high-temperature mechanical strength, grain boundary strength, and oxidation resistance, especially for large-size components, and often require costly elements like Re and rare earth metals.
Innovation Solution
An Ni-based casting superalloy composition is developed, including specific ranges of C, B, Hf, Zr, Al, Ta, Ti, Nb, Cr, Co, W, Mo, Si, and Fe, which optimizes grain boundary strengthening, solid solution strengthening, and oxidation resistance without relying on costly elements, allowing for single crystal or columnar grain structures with improved mechanical and oxidation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional Ni-based superalloys are used for high-temperature components, then high-temperature mechanical strength can be achieved, but oxidation resistance and grain boundary strength deteriorate
Solution Approach 1:
The patent optimizes the chemical composition parameters by precisely controlling the content ranges of multiple alloying elements (Al: 4.5-6.0 wt%, Cr: 8.0-10.0 wt%, Co: 5.0-7.0 wt%, W: 3.0-5.0 wt%, Mo: 0.5-1.0 wt%, Ti: 2.0-3.5 wt%, Nb: 0.5-1.5 wt%, Ta: 4.0-6.0 wt%). This parameter optimization resolves the contradiction by achieving a balanced composition that simultaneously provides high-temperature strength through γ′ phase precipitation and oxidation resistance through protective oxide scale formation.
Solution Approach 2:
The patent creates a composite microstructure consisting of γ-phase matrix and γ′-phase precipitates, where the γ-phase provides ductility and the γ′-phase provides strength. Additionally, the alloy forms a composite protective oxide scale on the surface containing multiple elements (Al2O3, Cr2O3, etc.) that works synergistically to provide excellent oxidation resistance while maintaining high-temperature mechanical properties.
2Strength
If costly elements like Re and rare earth metals are added to improve high-temperature strength, then mechanical strength improves, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive long-lived elements (Re, rare earth metals) with more economical alloying elements that achieve similar or better performance through optimized combinations. The use of conventional elements like Cr, W, Mo, and rare earth-free composition reduces raw material costs while maintaining or improving high-temperature properties through synergistic effects of multiple elements.
Solution Approach 2:
The patent changes the compositional parameters by eliminating Re and rare earth metal additions, instead achieving high-temperature strength through optimized content ranges of Al, Cr, Co, W, Mo, Ti, Nb, and Ta. This parameter change resolves the contradiction by demonstrating that costly elements are not necessary when composition is optimally balanced.
3Strength
If single crystal structure is achieved to maximize high-temperature strength, then mechanical strength improves, but manufacturing complexity and risk of misoriented grains increases
Solution Approach 1:
The patent optimizes chemical composition parameters to control solidification behavior and grain growth characteristics. The specific content ranges of alloying elements influence the solidification range, dendrite arm spacing, and grain boundary energy, which collectively facilitate single crystal formation and reduce the occurrence of misoriented grains during directional solidification, thereby reducing manufacturing complexity.
Solution Approach 2:
The patent creates local compositional variations that favor single crystal growth in the desired direction. The optimized alloy composition promotes preferential growth of grains with specific orientations while suppressing misoriented grain formation, enabling more reliable single crystal casting with reduced process complexity and higher yield.
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 new superalloy provides a cost-effective solution with enhanced high-temperature mechanical strength, grain boundary strength, and oxidation resistance, enabling the production of large-size components without solidification cracks, even when containing misoriented grains, thus improving the yield and reliability of high-temperature components.
Implementation Method 1
grain boundary strengthening which involves adding a grain boundary strengthening element (such as C (carbon), B (boron), Zr (zirconium) and Hf (hafnium))
Implementation Method 2
solid solution strengthening which involves dissolving a solid solution strengthening element (such as Cr (chromium), Co (cobalt), Mo (molybdenum) and W (tungsten)) in the γ-phase matrix to form a solid solution
Implementation Method 3
precipitation strengthening which involves dispersing fine γ′ (gamma prime)-phase precipitates (typically an Ni3Al phase in which an Al (aluminum) site thereof is sometimes substituted by Ti (titanium), Nb (niobium) or Ta (tantalum)) in a γ-phase (Ni-based solid solution phase) matrix
Implementation Method 4
high temperature components are required to have a higher oxidation resistance and a greater high-temperature mechanical strength than conventional components
Data Source
AI summary
It is an objective of the invention to provide a low cost Ni-based casting superalloy suitable for casting articles having a far better balance among a high-temperature mechanical strength, a grain boundary strength and a oxidation resistance than conventional Ni-based superalloy cast articles. There is provided an Ni-base casting super alloy including: in mass %, 0.03 to 0.15% of C; 0.005 to 0.04% of B; 0.01 to 1% of Hf; 0.05% or less of Zr; 3.5 to 4.9% of Al; 4.4 to 8% of Ta; 2.6 to 3.9% of Ti; 0.05 to 1% of Nb; 8 to 12% of Cr; 1 to 6.9% of Co; 4 to 10% of W; 0.1 to 0.95% of Mo; 0.02 to 1.1% of Si and/or 0.1 to 3% of Fe; and the balance including Ni and incidental impurities.