Dissimilar Alloy Stud Assembly for Hardened-to-Weldable Joining
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Welding dissimilar metal alloys, such as hardened and unhardened states, poses challenges due to the difficulty in joining materials that cannot be welded in their hardened state, particularly in aerospace applications where components often consist of different metal alloys.
Innovation Solution
A system comprising a hardened stud body made from an austenitic nickel-chromium-based alloy (e.g., INCONEL 718) and an unhardened stud subunit made from another alloy (e.g., INCONEL 625) is created, where the unhardened stud subunit is coupled to the hardened stud body and then heat-treated to achieve a strong and durable weld with a substrate, utilizing techniques like friction welding, inertia bonding, or gas tungsten arc welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If dissimilar metal alloys are welded in their hardened state, then the strength and hardness properties are maintained, but the welding process becomes difficult or impossible
Solution Approach 1:
The patent applies parameter changes by transitioning the material state from hardened to unhardened during the welding process. The stud is heated to austenitize the base metal, transforming its microstructure and properties temporarily to enable welding, then cooled to restore hardness. This dynamic parameter change allows the material to be weldable during joining while maintaining hardened properties in the final product.
Solution Approach 2:
The patent employs preliminary action by heating the stud to austenitize the base metal before welding occurs. This pre-heating step transforms the material structure in advance, making it suitable for welding. The austenitic phase is created as a preliminary state that facilitates the welding process, after which the material is cooled to achieve the desired hardened condition.
2Adaptability or versatility
If dissimilar materials are joined, then the functional requirements are met, but the welding compatibility decreases
Solution Approach 1:
The patent uses parameter changes to overcome dissimilar material incompatibility. By heating to austenitize the base metal, the patent creates a temporary state where different alloys (such as Inconel 718 and Inconel 625) become more compatible for welding. The austenitic phase allows dissimilar materials to be joined reliably, and subsequent cooling restores the desired material properties.
Solution Approach 2:
The patent effectively creates a composite structure by joining dissimilar alloys (e.g., hardened Inconel 718 stud body with unhardened Inconel 625 subunit). This composite approach allows each material to contribute its advantageous properties - the hardened stud body provides strength and hardness, while the unhardened subunit provides weldability and bonding capability to the substrate.
3Device complexity
If a single material is used for the entire stud, then the manufacturing process is simplified, but the ability to maintain hardness while enabling welding is lost
Solution Approach 1:
The patent applies segmentation by dividing the stud into two distinct parts: a hardened stud body and an unhardened subunit. This segmentation allows each portion to have optimized properties - the stud body maintains hardened characteristics for strength, while the subunit remains unhardened for ease of welding to the substrate. The interface between these segments is joined through welding after the subunit is attached to the hardened body.
Solution Approach 2:
The patent creates a composite structure with a hardened stud body made from one alloy composition and an unhardened subunit made from another alloy composition. This composite construction enables the assembly to simultaneously possess hardness (from the stud body) and weldability (from the subunit), overcoming the limitation of using a single material for the entire component.
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
This approach allows for the successful welding of hardened materials to unhardened substrates, leveraging the strength and durability of the weld between the unhardened subunit and substrate while maintaining the beneficial hardness properties of the hardened stud body, thus overcoming the limitations of welding dissimilar materials in their hardened states.
Implementation Method 1
The unhardened stud subunit may be at least one of friction welded, inertia bonded, explosive welded, resistance welded, laser welded, gas tungsten arc welded, or brazed to an unhardened stud body
Implementation Method 2
The unhardened stud body may undergo a heat treatment to become the hardened stud body
Implementation Method 3
The heat treating may comprise a precipitation heat treatment
Implementation Method 4
The unhardened stud subunit may be at least one of friction welded
Data Source
AI summary
A system is provided comprising a hardened stud body and an unhardened stud subunit coupled to the hardened stud body. The hardened stud body may comprise a first composition having by weight between 17% and 21% chromium, between 2.8% and 3.3% molybdenum, between 50% to 55% nickel, and between 4.75% and 5.5% niobium. The unhardened stud subunit may comprise a second composition having by weight between 20% and 23% chromium, between 8% and 10% molybdenum, at least 58% nickel, and between 3.15% and 4.15% niobium.