Cellular Gamma Prime Superalloy Grain Boundary Design
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Solution Overview
Problem
Current nickel-base superalloys face challenges in achieving balanced improvements in creep and dwell fatigue crack growth resistance at elevated temperatures, with existing heat treatment methods often compromising between creep and fatigue properties, and requiring complex processing schedules.
Innovation Solution
A gamma prime nickel-base superalloy with cellular gamma prime precipitates that form serrated or convoluted irregular grain boundaries, achieved through a solution heat treatment and quench process, allowing for improved high-temperature dwell capabilities without the need for slow cooling rates and high temperature holds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If slow cooling rates and high temperature holds are used during heat treatment, then fatigue crack growth resistance is improved, but creep resistance deteriorates and processing time increases
Solution Approach 1:
The patent applies parameter changes by modifying the cooling rate and heat treatment temperature parameters to achieve cellular gamma prime precipitates. Specifically, the alloy is cooled at rates between 100-500°F per minute from solution heat treatment temperatures of 2100-2300°F, which is faster than conventional methods. This parameter change produces cellular precipitates that create tortuous grain boundaries, improving fatigue crack growth resistance without requiring slow cooling or extended high-temperature holds, thus reducing processing time while maintaining reliability.
2Ease of manufacture
If conventional heat treatment methods are used, then processing is simpler, but a balance must be compromised between creep and fatigue properties
Solution Approach 1:
The patent changes the heat treatment parameters to solution heat treat at 2100-2300°F followed by cooling at 100-500°F per minute, which produces cellular gamma prime precipitates. This parameter change achieves superior combined creep and fatigue performance while maintaining relatively simple processing. The cellular precipitates form during this controlled cooling, creating tortuous grain boundaries that simultaneously improve fatigue crack growth resistance and maintain creep resistance, eliminating the need to compromise between these properties as in conventional methods.
3Reliability
If cellular gamma prime precipitates are formed, then tortuous grain boundary fracture paths are created improving fatigue resistance, but the alloy composition and processing must be precisely controlled
Solution Approach 1:
The patent specifies precise parameter ranges to form cellular gamma prime precipitates: cooling rates of 100-500°F per minute and solution heat treatment temperatures of 2100-2300°F. These parameter changes must be tightly controlled to achieve the desired cellular precipitate morphology. The alloy composition is also precisely controlled with specific ranges for aluminum (2.0-4.0%), titanium (2.0-6.0%), and other elements to ensure cellular precipitate formation during the heat treatment process, achieving improved fatigue resistance through controlled manufacturing precision.
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 superalloy exhibits enhanced creep and fatigue crack growth resistance at temperatures above 1200°F (650°C), with good producibility and thermal stability, and maintains these properties across various cooling rates, promoting a tortuous grain boundary fracture path for improved mechanical performance.
Implementation Method 1
achieved through a solution heat treatment and quench process
Implementation Method 2
cellular gamma prime precipitates that form serrated or convoluted irregular grain boundaries
Implementation Method 3
cellular gamma prime precipitates that form serrated or convoluted irregular grain boundaries... promoting a tortuous grain boundary fracture path
Implementation Method 4
enhanced creep and fatigue crack growth resistance at temperatures above 1200°F (650°C)
Data Source
Figure 1
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Figure 4
AI summary
A gamma prime nickel-base superalloy and components formed therefrom that exhibit improved high-temperature dwell capabilities, including creep and dwell fatigue crack growth behavior. The superalloy contains, by weight, 10.00 to 22.0% cobalt, 10.0 to 14.0% chromium, 4.0 to 6.0% tantalum, 2.0 to 4.0% aluminum, 2.0 to 6.0%) titanium, 1.5 to 5.0% tungsten, 1.5 to 5.0% molybdenum, 1.0 to 3.5% niobium, 0.05 to 0.6% hafnium, 0.02 to 0.10% carbon, 0.01 to 0.40 % boron, 0.02 to 0.10% zirconium, the balance essentially nickel and impurities, wherein the titanium: aluminum weight ratio is 0.7 to 1.5. The superalloy is hot worked and heat treated to contain cellular gamma prime precipitates that distort grain boundaries, creating tortuous grain boundary fracture paths that are believed to promote the fatigue crack growth resistance of the superalloy.