Super Alloy Chemistry for Fusion Weldability
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Solution Overview
Problem
High strength and oxidation resistant alloys, such as nickel-based super alloys, exhibit poor fusion weldability due to liquation cracking and strain age cracking (SAC), limiting the repair of turbomachine components with cavities larger than 0.250″, as conventional metal chemistries fail to prevent cracking during welding.
Innovation Solution
A metal chemistry comprising specific weight percentages of chromium, cobalt, molybdenum, iron, aluminum, titanium, manganese, carbon, and a titanium+aluminum alloy, which forms a precipitated strengthened gamma prime phase, enhancing weldability and resistance to SAC, allowing for the repair of larger cavities and pits in turbomachine components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional metal chemistry is used for nickel-based super alloys, then strength and oxidation resistance are improved, but fusion weldability deteriorates due to liquation cracking and strain age cracking
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the filler metal, specifically controlling the aluminum content (3.0-6.0 wt%), titanium content (1.5-3.0 wt%), and gamma prime forming element ratios to achieve optimal weldability while maintaining strength. This resolves the contradiction by adjusting compositional parameters to prevent cracking during welding.
Solution Approach 2:
The patent uses composite material principles by creating a filler metal with a complex multi-element composition including nickel, chromium, cobalt, molybdenum, aluminum, titanium, and other alloying elements. This composite chemistry enables the material to simultaneously achieve strength, oxidation resistance, and improved weldability by distributing functions across multiple elements.
2Strength
If aluminum content is increased to improve strength, then gamma prime fraction increases, but strain age cracking tendency increases
Solution Approach 1:
The patent applies parameter changes by optimizing the aluminum content within a specific range (3.0-6.0 wt%) and controlling the ratio of aluminum to titanium and other gamma prime forming elements. This controlled parameter adjustment ensures sufficient gamma prime phase for strength while preventing excessive gamma prime that would cause strain age cracking.
Solution Approach 2:
The patent applies local quality by creating different compositional regions within the weld metal, particularly in the weld metal adjacent to fusion boundary (WMATFB) region. The filler metal chemistry is designed to create a local composition that falls within the weldable material region, preventing SAC in critical areas while maintaining overall strength.
3Ease of manufacture
If filler metal chemistry is optimized for weldability, then cracking tendency is reduced, but repair capability for large cavities is limited
Solution Approach 1:
The patent applies parameter changes by adjusting the filler metal composition to have moderate aluminum (3.0-6.0 wt%) and titanium (1.5-3.0 wt%) content, along with specific amounts of strengthening elements like molybdenum (3.0-6.0 wt%) and cobalt (3.0-6.0 wt%). This compositional parameter optimization enables the filler metal to be used for repairing cavities of various sizes, from small defects to large cavities exceeding 0.250 inches in diameter.
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 proposed metal chemistry effectively prevents strain age cracking, enabling the repair of cavities up to 1″ or more in diameter, thereby extending the life of turbomachine components and reducing costs by preventing component failure and discarding.
Implementation Method 1
an amount of a titanium+aluminum alloy of between about 0.55% and about 2.75% by weight
Implementation Method 2
forms a precipitated strengthened gamma prime phase
Data Source
AI summary
A metal chemistry includes an amount of chromium weight of between about 9.0% and about 16% by weight, an amount of cobalt of between about 7.0% and about 14% by weight, an amount of molybdenum of between about 10% and about 20% by weight, an amount of iron of between about 1.0% and about 5.0% by weight, an amount of aluminum of between about 0.05% and about 0.75% by weight, an amount of titanium of between about 0.5% and about 2.0% by weight, an amount of manganese not to exceed about 0.8% by weight, an amount of carbon of between about 0.02% and about 0.10% by weight, an amount of a titanium+aluminum alloy of between about 0.55% and about 2.75% by weight, and an amount of nickel.