Ni-Based Superalloy Hot Working for Crack-Free Fine Microstructures
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Solution Overview
Problem
Ni-based superalloys with a large amount of γ' phase face challenges in hot workability, leading to increased deformation resistance and the risk of cracks during hot working, making it difficult to produce high-strength components for aircraft engines and gas turbines efficiently.
Innovation Solution
A method is developed to control the heating process, mold surface temperature, and strain rate during hot working to suppress γ' phase precipitation and maintain a stable temperature, thereby preventing coarsening and incipient melting of crystal grains, ensuring homogeneous microstructures and improved hot workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the amount of γ' phase is increased to improve strength and durable temperature, then the material strength increases, but hot workability deteriorates and deformation resistance increases causing cracks during hot working
Solution Approach 1:
The invention changes the chemical composition parameters by strictly controlling the content of Al (1.0-4.0%), Ti (3.0-7.0%), and other alloying elements. This parameter optimization ensures the γ' phase content is maintained at 30-50% at 760°C, achieving the optimal balance between strength and hot workability. The controlled composition prevents excessive γ' phase formation that would cause cracking during hot working.
Solution Approach 2:
The invention applies dynamic temperature control during hot working by maintaining the material temperature within 1000-1150°C and controlling the cooling rate to 20-200°C/min. This dynamic temperature management prevents premature precipitation of γ' phase during processing, reducing deformation resistance and enabling successful hot working of high-strength alloys.
2Strength
If the grain size of γ phase is reduced to improve yield strength and fatigue strength, then mechanical characteristics improve, but it becomes much more difficult to strictly control the grain size as the size of materials is increased
Solution Approach 1:
The invention uses chemical composition parameters (particularly Al and Ti content) as control levers to influence grain size. By optimizing the alloying element content within specific ranges, the grain size of γ phase is controlled at 5-20 μm for large-size components, achieving fine-grain microstructure even in large-scale materials where traditional grain size control becomes difficult.
Solution Approach 2:
The invention performs preliminary grain size control through optimized chemical composition design before the hot working process. The controlled alloying element content prepares the material with appropriate stacking fault energy and phase distribution, enabling subsequent hot working to produce uniform fine-grain structures in large components without requiring complex post-processing.
3Strength
If the amount of Al, Ti, Nb, or Ta is increased to increase the amount of γ' phase, then material strength increases, but it becomes difficult to perform hot working and cracks occur in the hot working material
Solution Approach 1:
The invention optimizes the chemical composition parameters by setting specific content ranges for Al (1.0-4.0%), Ti (3.0-7.0%), Nb (0.0-3.0%), and Ta (0.0-3.0%). This parameter optimization ensures the γ' phase content is maintained at 30-50% at 760°C, achieving the optimal balance between strength and hot workability. The controlled composition prevents excessive γ' phase formation that would cause cracking during hot working.
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 method enhances the yield of high-strength Ni-based superalloys with improved hot workability, reducing the risk of surface cracks and allowing for increased operation temperatures, contributing to more efficient heat engine performance.
Implementation Method 1
suppress γ' phase precipitation
Implementation Method 2
mold surface temperature
Implementation Method 3
prevent coarsening and incipient melting of crystal grains
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Provide is a production method whereby it is possible to obtain a high-strength Ni-based superalloy which is used in an aircraft engine or a gas turbine for power generation and which has good hot workability and a homogeneous microstructure. The method is a method of producing a Ni-based superalloy in which a hot working material of a Ni-based superalloy is subjected to hot working with a die heated to a temperature, the hot working material having a composition consisting of, in mass%, 0.001 to 0.050% of C, 1.0% to 4.0% of Al, 3.0% to 7.0% of Ti, 12% to 18% of Cr, 12% to 30% of Co, 1.5% to 5.5% of Mo, 0.5% to 2.5% of W, 0.001% to 0.050% of B, 0.001% to 0.100% of Zr, 0% to 0.01% of Mg, 0% to 5% of Fe, 0% to 3% of Ta, 0% to 3% of Nb, and the remainder of Ni and impurities, the method including: a hot working material heating step of heating and holding the hot working material in a temperature range of 950°C to 1150°C for 1 hour or longer; and a hot working step of performing hot working on the hot working material with the die that is heated to the temperature in a range of 800°C to 1150°C.