Buffer Layer Welding for Crack-Resistant Diffusion-Bonded Joints
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Solution Overview
Problem
The ductility of diffusion bonded joints decreases at high temperatures during fusion welding, leading to increased cracking sensitivity compared to the base metal parts, causing strain-induced cracking in the joints.
Innovation Solution
A welding method that involves forming a buffer layer with higher ductility than the diffusion bonded joints in the welding region, which absorbs and buffers the strain caused by fusion welding, using techniques such as overlay welding, powder sintering, or ultrasonic welding, to prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fusion welding is performed on diffusion bonded joints, then the diffusion bonded structure can be assembled with other parts, but the ductility of the diffusion bonded joint decreases at high temperature leading to cracking sensitivity
Solution Approach 1:
A buffer layer is formed on the diffusion bonded joint surface before fusion welding takes place. This preliminary action prepares the joint to withstand the thermal stresses of subsequent welding by providing a ductile interface that can accommodate strain, preventing cracking during the welding process.
Solution Approach 2:
The buffer layer acts as an intermediary between the diffusion bonded joint and the fusion welding process. It absorbs and buffers the strain generated during welding, protecting the brittle diffusion bonded joint from direct exposure to high thermal stresses while still allowing the welding to proceed.
2Reliability
If a buffer layer is formed to absorb strain during welding, then cracking in diffusion bonded joints can be suppressed, but additional manufacturing steps are required
Solution Approach 1:
The buffer layer changes the physical and mechanical parameters of the joint surface by introducing a layer with higher ductility and different thermal properties. This parameter change allows the joint to better withstand welding stresses without requiring fundamental changes to the welding process itself.
Solution Approach 2:
The buffer layer creates a composite structure at the joint interface, combining the diffusion bonded joint material with a buffer material that has complementary properties. This composite approach leverages the strengths of both materials to achieve crack resistance during welding.
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 buffer layer effectively suppresses cracking in diffusion bonded joints by absorbing strain, maintaining joint integrity even under high temperature conditions, and can be formed using various methods like friction stir welding or brazing to reduce strain and prevent ductility dip cracking.
Implementation Method 1
the buffer layer absorbs and buffers strain caused by the fusion welding
Implementation Method 2
the buffer layer may be formed by overlay welding
Implementation Method 3
the buffer layer may be formed by any one of processes of powder sintering, ultrasonic welding, friction welding
Implementation Method 4
the buffer layer may be formed by any one of processes of powder sintering, ultrasonic welding, friction welding, friction surfacing, friction stir welding
Implementation Method 5
a diffusion bonded structure formed by diffusion bonding metal parts to each other
Data Source
Figure 1~2(b)
Figure 3~5
Figure 6(a)~6(b)
AI summary
A welding method of a diffusion bonded structure in which the diffusion bonded structure formed by diffusion bonding metal parts to each other is bonded to another part by fusion welding includes a buffer layer forming step (S10) of forming a buffer layer in a welding region including a diffusion bonded joint of the diffusion bonded structure, the buffer layer having greater ductility than the diffusion bonded joint, and a welding step (S12) of bonding the welding region in which the buffer layer is formed to the another part by performing the fusion welding from above the buffer layer.