Laser Brazing
Laser brazing is a precision joining process in which laser energy is used to melt a filler material that joins metallic components – without the base materials having to be melted.
The controlled and localised heat input makes the technology particularly suitable for applications with high requirements for joint quality, surface finish, dimensional accuracy and low thermal impact.
Here we explain how laser brazing works, which materials and applications the technology is suitable for, and what is important when designing an industrial laser brazing system.
What is laser brazing?
Laser brazing is a joining process in which a concentrated laser beam is used as a heat source to melt a filler material, also known as brazing filler metal. The molten filler material wets the surfaces of the base materials and flows into the joint, where it solidifies and joins the components.
Unlike laser welding, the base materials do not need to be melted. The process can therefore result in significantly lower thermal impact on the components and reduce the risk of distortion.
At the same time, the high precision of the laser beam makes it possible to control the heat input within a very limited area.
Laser brazing is therefore particularly suitable for components requiring:
- high dimensional accuracy
- limited heat input
- low distortion
- high and consistent joint quality
- leak-tight joints
- excellent surface finish
- high repeatability
How does laser brazing work?
During laser brazing, the laser beam is focused on the area where the components are to be joined. Filler material is usually supplied in the form of wire or powder and heated by the laser energy until it melts.
The molten filler material wets the surfaces of the components and flows into the joint. As the laser beam and filler material move along the joint, the filler metal solidifies and forms the bond between the components.
For a stable process, the temperature must be high enough to melt the filler material and achieve good wetting, while at the same time being controlled so that unnecessary melting of the base material is avoided.
The process result is influenced by factors including:
- laser power
- process speed
- focal position and beam diameter
- filler material
- wire or powder feed rate
- material combination
- joint geometry
- surface condition of the components
- fixturing
- shielding gas, where applicable
It is the interaction between these factors that determines joint quality and process stability.
Laser brazing compared with laser welding
Laser brazing and laser welding both use laser radiation as a concentrated heat source, but the actual joining principles are different.
In laser welding, the base materials are locally melted and form the weld joint. The process can be performed with or without filler material.
In laser brazing, a filler material with a lower melting temperature than the base material is melted instead. The base materials therefore do not need to be melted in order to join the components.
This gives laser brazing some distinct characteristics:
| Property | Laser brazing | Laser welding |
|---|---|---|
| Base material | Normally does not need to be melted | Locally melted |
| Filler material | Required | Not always required |
| Heat input | Highly controlled | Concentrated but generally higher |
| Distortion | Usually low | Usually low compared with conventional welding |
| Joint appearance | Excellent surface finish possible | Depends on process and joint |
| Penetration depth | Limited | Can be deep |
| Typical application | Joints requiring high surface quality and low thermal impact | Structural and technical welded joints |
The most suitable process therefore depends on the component, materials and the mechanical, thermal and aesthetic requirements of the joint.
Benefits of industrial laser brazing
Controlled heat input
The laser beam makes it possible to concentrate the energy within a limited area and control the process with high precision.
Low distortion
Because the base material normally does not need to be melted, the total thermal impact can be limited. This is particularly valuable for thin or dimensionally sensitive components.
High joint quality
With the correct materials, joint design and process parameters, laser brazing can produce consistent, leak-tight and repeatable joints.
Excellent surface finish
The process can produce very smooth and aesthetically attractive joints, potentially reducing the need for post-processing.
High repeatability
Laser energy, motion and filler material feed can be controlled very precisely, making the process well suited to automated series production.
Excellent potential for automation
Laser brazing can be integrated with multi-axis motion systems, robots, component handling and other production equipment.
Typical applications
Laser brazing is used in industrial applications where high joint quality needs to be combined with controlled heat input and high repeatability.
Typical applications include:
- automotive industry
- aerospace industry
- energy industry
- marine and offshore
- machinery and engineering industries
- precision components
- tools and wear parts
- repair and restoration of technical components
- automated series production
In the automotive industry, laser brazing is used, among other applications, where joint appearance and dimensional accuracy are important, for example on visible body joints.
Materials and filler materials
Laser brazing can be used with a variety of metallic materials and material combinations.
Examples include:
- carbon steel
- stainless steel
- high-strength steels
- titanium alloys
- nickel-based alloys
- cobalt-based alloys
- certain carbide-based materials and composites
The filler material must be selected to suit the base material and the properties required of the finished joint.
The choice influences factors including:
- wetting
- joint strength
- corrosion properties
- operating temperature
- wear resistance
- joint appearance
- process temperature window
The combination of base material and filler material should therefore be evaluated together as part of process development.
Joint design and component quality
A stable laser brazing process requires the components, filler material and joint geometry to work together.
The joint surfaces must be suitable for good wetting and should be free from contaminants that could affect the process.
Important factors include:
- joint geometry
- gap between components
- component position
- surface condition
- oxides and contaminants
- fixturing
- filler material feeding and positioning
Accurate and repeatable component positioning is particularly important in automated systems.
Wire or powder as filler material
The filler material can be supplied in different ways depending on the application.
Wire feeding
In wire-based laser brazing, the filler material is continuously fed into the process zone. The position and feed rate of the wire must be synchronised with the laser beam and movement along the joint.
The method is well suited to continuous and automated processes.
Powder feeding
Filler material can also be supplied in powder form. The powder is transported to the process area and melted by the laser beam.
The most suitable method depends on the component, material, joint geometry and type of process.
What affects the result in laser brazing?
A stable and repeatable result requires several process parameters to be balanced against each other.
Important factors include:
- laser power
- process speed
- beam diameter and power density
- focal position
- filler material
- feed rate
- joint geometry
- joint gap
- component position
- fixturing
- surface condition
- shielding gas
- desired joint geometry
Excessive heat input can affect the base material or impair the properties of the joint, while insufficient heat input can result in inadequate melting and wetting.
The process window must therefore be established for the specific combination of component, base material and filler material.
Automation of laser brazing
Laser brazing is well suited to automation because laser energy, motion and filler material feed can all be controlled with high precision.
An automated system may, for example, include:
- laser source
- process optics
- wire or powder feeder
- fixturing
- XY motion system
- multi-axis motion system
- industrial robot
- component handling
- camera or sensors
- process monitoring
- control system
- laser safety enclosure
The design of the system depends on component geometry, production volume, quality requirements and the required level of automation.
Safety in laser brazing
Industrial laser brazing uses high-power laser radiation and therefore requires a safety solution adapted to the specific laser and process.
Laser systems with an open beam path can present hazards from both direct and reflected laser radiation.
An automated installation can be designed with features such as:
- laser safety enclosure
- interlocked doors and access panels
- laser-rated protective barriers
- extraction of fumes and particles
- documented operating procedures
- trained personnel
- application-specific risk assessment
A correctly designed and enclosed system can be configured as a Class 1 laser product during normal operation, even though the process laser itself is Class 4.
LMI also offers training in laser safety.
Customised laser brazing systems
Laser brazing is a process that often needs to be adapted to the specific component, material combination, joint geometry and production requirements.
LMI therefore provides customised laser brazing system solutions, where the equipment is designed around the actual application rather than based on a standardised machine.
A solution may include:
- suitable laser source
- process optics
- wire or powder feeding
- fixturing
- XY or multi-axis motion
- robot integration
- component handling
- process monitoring
- control system
- laser safety
- integration with other production equipment
LMI works with Preco, among others, which develops modular and customised system platforms for industrial laser processing. These platforms can be configured and integrated according to the requirements of the specific process and production environment.
The right solution starts with the application
In laser brazing, the result is not determined solely by laser power or the technical specifications of the machine.
Materials, filler material, joint design, component positioning, heat input and motion all need to work together to create a stable and repeatable process.
A laser brazing system should therefore be specified based on the actual component and requirements for factors such as:
- joint quality
- strength
- leak tightness
- surface finish
- dimensional accuracy
- cycle time
- production volume
- repeatability
- automation
Through testing and process development, the equipment and process can be adapted before the final system solution is specified.
Laser brazing adapted to your production
LMI helps you evaluate the component, materials, filler material, joint geometry and production requirements in order to develop a technically and economically suitable solution.
Because our laser brazing solutions are customised, we use your application and your production requirements as the basis when designing the system.
Contact us to discuss your application.
Frequently asked questions about laser brazing
What is laser brazing?
Laser brazing is a joining process in which a laser is used as the heat source to melt a filler material that joins the components. The base material normally does not need to be melted.
What is the difference between laser brazing and laser welding?
In laser welding, the base material is locally melted to form the weld joint. In laser brazing, a filler material with a lower melting temperature is melted instead, while the base material normally remains solid.
What are the advantages of laser brazing?
The process provides highly controlled heat input and can offer low distortion, high dimensional accuracy, excellent surface finish and high repeatability.
Which materials can be laser brazed?
The process can be used with several types of steel as well as nickel-, cobalt- and titanium-based materials, among others. Practical suitability depends on the combination of base material, filler material and the requirements of the finished joint.
Is filler material always used in laser brazing?
Yes. The filler material is a fundamental part of the brazing process and has a lower melting temperature than the materials being joined.
Can laser brazing be automated?
Yes. The process is very well suited to automation and can be integrated with XY systems, multi-axis motion systems, industrial robots and automated component handling.
Should the application be tested before a system is specified?
Testing is recommended. It makes it possible to evaluate the material combination, filler material, joint geometry, laser power, process speed and feeding parameters before the final system solution is specified.
Contact LMI about laser brazing
Do you have a component or production process where laser brazing could be a suitable solution?
LMI can help you analyse the application and evaluate materials, filler material, joint geometry, process and automation requirements to develop a suitable industrial laser brazing solution.
Contact us to discuss your application.
