Thermal Sprayed Interlayers for Welding Unweldable Materials
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Solution Overview
Problem
Current technologies lack a reliable thermal welding method for joining dissimilar materials in multi-material designs, particularly those involving non-weldable combinations like metals with glass, wood, or plastics, due to issues such as hot cracking, liquid metal embrittlement, and microstructure destruction during welding.
Innovation Solution
Applying a metallic thermal sprayed layer with defined thickness and surface roughness on the non-weldable material, followed by a thermal joining process that only welds the sprayed layer with the metallic material, using techniques like arc or beam welding in a lap joint configuration to avoid overheating and critical temperature zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct thermal welding is used to join dissimilar materials, then welding speed and productivity are improved, but material degradation and weld defects occur due to excessive heat input
Solution Approach 1:
A transition layer is introduced between the dissimilar materials to be joined. This intermediate layer has thermal and mechanical properties that are suitable for both materials, allowing thermal welding to proceed at high speed while the transition layer absorbs and distributes heat to prevent excessive thermal input to the base materials, thereby avoiding material degradation and weld defects
Solution Approach 2:
The thermal and mechanical parameters of the joint are modified by introducing a transition layer with specific properties. This layer changes the heat distribution parameters and stress distribution parameters, enabling high-speed welding without the harmful effects of direct thermal contact between dissimilar materials
2Strength
If high heat input is used during welding to ensure complete fusion, then joint strength is improved, but hot cracking and liquid metal embrittlement occur in the heat affected zone
Solution Approach 1:
The transition layer serves as a heat buffer between the welding zone and the base materials. It allows sufficient heat for complete fusion and strong joint formation while simultaneously limiting heat transmission to the heat affected zone, preventing hot cracking and liquid metal embrittlement that would occur with direct high heat input to the base materials
Solution Approach 2:
Different regions of the joint are given different thermal properties through the transition layer. The region near the weld pool receives sufficient heat for strong fusion, while the heat affected zone is protected by the transition layer's thermal barrier properties, creating local quality differences in heat distribution that prevent cracking and embrittlement
3Reliability
If conventional bonding or mechanical joining is used for unweldable material combinations, then material integrity is preserved, but manufacturing complexity and production time increase
Solution Approach 1:
The transition layer enables thermal welding to be used instead of complex bonding or mechanical joining processes. This intermediate layer makes the materials compatible for thermal welding, simplifying the manufacturing process while maintaining material integrity through controlled heat distribution
Solution Approach 2:
By changing the thermal and mechanical parameters through the introduction of a transition layer, unweldable material combinations become weldable. This parameter modification allows the use of simple, fast thermal welding processes instead of complex bonding or mechanical joining, reducing manufacturing complexity while preserving material integrity
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
Enables successful welding of previously unweldable material combinations by controlling temperature and stress, preventing defects like hot cracks, embrittlement, and corrosion, while improving weld quality and reducing material degradation.
Implementation Method 1
A metallic thermal sprayed layer is applied on the surface of the non-weldable material
Implementation Method 2
the thermal sprayed layer has a similar or nearly similar alloy composition to the metallic material... the contact area between the thermal sprayed metallic layer and the metallic material is welded together
Data Source
Figure 1~2
Figure 3~4
AI summary
Method for joining of at least two unweldable materials, non-weldable directly to each other with thermal joining processes in a lap joint configuration, where a two step sequence is used consisting of a first step to apply a thermomechanical or mechanical surface protection layer on the surface of an unweldable material and a second step, where a thermal joining process is used to joint the sprayed layer with an applied layer sheet.