Titanium Nitride Coated Ti Welding via Ti-N Connection Zone
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Solution Overview
Problem
The formation of resistive films on titanium-containing components can lead to high impedance failures and shortened battery life, and existing protective coatings like titanium nitride interfere with the formation of strong metallurgical bonds during welding, making it challenging to achieve reliable weld joints using resistance spot welding (RSW).
Innovation Solution
A thermal nitriding process is used to apply a titanium nitride coating on Ti-containing components, and a region of the coating is conditioned to form a Ti—N solid solution alloy connection zone with a lower liquidus temperature and higher electrical resistance, allowing for the formation of strong and reliable welds using RSW by heating the connection zone with a laser before welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective coating layer of titanium nitride is applied to the Ti-containing component using thermal nitriding, then the component is protected from resistive film formation, but the presence of titanium nitride at the weld interface interferes with the formation of strong metallurgical bonds during resistance spot welding
Solution Approach 1:
The patent applies preliminary action by depositing the titanium nitride protective coating on the Ti-containing component before the welding process. This allows the component to gain corrosion protection while the welding process is subsequently optimized to penetrate through the coating. The preliminary coating application does not prevent welding, but requires a two-stage approach: first coating deposition, then welding with controlled parameters to achieve metallurgical bonding despite the coating presence.
Solution Approach 2:
The patent employs parameter changes by modifying the welding process parameters (current, voltage, time, pressure) to account for the presence of the titanium nitride coating. The welding parameters are adjusted to ensure sufficient energy input to melt through the coating and create a proper weld pool, while controlling the cooling rate to achieve the desired microstructure and mechanical properties in the weld zone.
2Ease of manufacture
If vapor deposition or sputtering processes are used to precisely deposit titanium nitride only on non-weld regions, then weldability is improved, but manufacturing cost increases and production speed decreases
Solution Approach 1:
The patent applies universality by using the thermal nitriding process to deposit titanium nitride coating on the entire surface of the component, serving multiple functions: providing corrosion protection to all exposed surfaces and creating a uniform coating that can be consistently welded. This eliminates the need for separate selective coating processes for different regions, simplifying the manufacturing workflow while maintaining both protective functionality and weldability.
Solution Approach 2:
The patent employs this principle by choosing thermal nitriding, a cost-effective and rapid coating method, over expensive vapor deposition or sputtering processes. The thermal nitriding process uses relatively simple equipment and shorter cycle times, making it economically viable for production. The coating is applied broadly rather than selectively, accepting that some coating will be present at weld zones but compensating through optimized welding parameters.
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 method enables the formation of strong and reliable welds between Ti-containing components, particularly suitable for implantable medical devices, with improved manufacturing efficiency and reduced costs, as evidenced by increased microhardness and pull test failure loads of the weld joints.
Implementation Method 1
manufacturing costs can be reduced by applying a protective coating including titanium nitride to surfaces of a first Ti-containing component using a thermal nitriding process
Implementation Method 2
heating the connection zone with a laser before welding
Implementation Method 3
the presence of titanium nitride at the weld interface is particularly challenging for resistance spot welding (RSW) due to the difficulty in melting and dissolving the titanium nitride film
Implementation Method 4
the presence of titanium nitride at the weld interface is particularly challenging for resistance spot welding (RSW)
Data Source
AI summary
A workpiece of Ti or a Ti alloy includes a surface with a coating layer of titanium nitride. A region of the surface includes a connection zone of a Ti—N solid solution alloy. A second Ti or Ti alloy workpiece is contacted with the connection zone, and a weld joint is formed across the connection zone with a resistance welding process. The weld joint extends into the first Ti workpiece and the second Ti workpiece.