Laser Metal Deposition: 7 Important Factors Related To It


  • What is laser metal deposition?
  • How does the process of laser metal deposition work?
  • What are the advantages of laser metal deposition?
  • What is the work of fiber lasers in LMD?
  • What are the applications of laser metal deposition?
  • Flexible features for metal and alloy components in LMD
  • Why are CO2 lasers not used for LMD?

What is laser metal deposition?

Laser metal deposition or LMD refers to the process of forming a pool of melted metal on a metallic substrate with the help of a laser. A gas stream is used for injecting metal powder into the substrate. This absorbed metal powder forms a metal deposit on the substrate of the metal. This process of additive manufacturing is used for several purposes such as repairing metal components, molding metal or alloy tools, metal screws, valves, etc. Laser metal deposition is becoming a widely used technique in the field of manufacturing.

laser metal deposition
Metal layer deposition on a surface by LMD. Image source: http://Firstcomer, Роботизированная лазерная наплавка в импульсном режиме, CC BY-SA 4.0

How does the process of laser metal deposition work?

The laser metal deposition process involves the use of lateral or coaxial nozzles for blowing powder into the process zone of the metal. Generally, the powder used for laser cladding is metallic in nature. The powder interacts with the laser beam which preheats the particles to their melting points. The melted powder then forms the metal pool on the surface. This metal pool is later cooled to form a metallic layer on the surface as required. At times the substrate is moved for solidifying the metallic deposition.

The substrate motion is controlled by using the CAD or Computer-aided Design system. It is used for implanting solid materials into a pattern of tracks. The desired pattern is obtained after the trajectory ends. In some designs, the laser or nozzle system is movable and moves over a stationary substrate to produce solidified tracks. Multiple layers are built one over the other in order to form a three-dimensional component. Geometrical accuracy is high for this process.

Laser Cladding nozzle configurations
4 different types of metallic powder feeding systems. !. Wire system, 2. Lateral nozzle system, 3. Radial nozzle system, 4. conical nozzle system. Image source: MaterialgeezaLaser Cladding nozzle configurationsCC BY-SA 3.0

What are the advantages of laser metal deposition?

The process of laser metal deposition has been gaining more popularity in recent years over processes like thermal spraying and gas metal arc welding because:

  • This process is a well-suited method for objects of any shape and structure.
  • This process creates less distortion from the required trajectory.
  • This process does not dissipate much heat reducing the heat damage in materials.
  • This process is used for obtaining low dilution between the substrate and tracks, and simultaneously establishing a strong metallurgical bond.
  • This process has a high cooling rate which produces fine microstructures.
  • This process allows great control over the laser power supply and laser trajectory.
  • The structure formed by this process is devoid of crack and porosity.
  • This process uses compact technology.
  • This process is appropriate for the graded material application.
  • This process is well-suited for near-net-shape manufacturing.
  • For repairing parts, this process provides particular dispositions.

What is the role of fiber lasers in LMD?

Fiber lasers, also known as optical fiber lasers are based on the principle of total internal reflection (TIR). It uses the TIR phenomenon in optical fibers for transmitting light. These lasers are capable of transmitting light over large distances and also helps to reduce the distortion of laser beam caused by thermal effects. Optical Fiber-based lasers are capable of providing higher output power than the other different laser variants. These lasers are required to have a high surface area to volume ratio for providing continual output power of kilowatt range with effective cooling. The optical fiber waveguide is used for reducing the optical path distortion caused by thermal issues. These lasers are far more controllable, reliable, and consistent compared to other types of lasers (Carbon dioxide or Nd:YAG lasers).

Optical fiber lasers. Image source: http://Ken-ichi Ueda – from author 3 fiber disk lasers, fiber lasers with transversal delivery of pump.

What are the applications of laser metal deposition?

Laser metal deposition or LMD is used for a number of industrial manufacturing operations. The process has been gaining more popularity in recent years over processes like thermal spraying and gas metal arc welding. Some of the widespread applications of laser metal depositing:

  1. It is used for sintered tool repairing.
  2. It is used for aerospace and automobile component repairing.
  3. It is used for turbine blade repair.
  4. It is used for the surface coating of oil drilling instruments.
  5. It is used for medical implant manufacturing and repairing.
  6. It is used for rapid prototyping.
  7. It is used for metal matrix composite fabrication.
  8. It is used for self-lubricating surface production.
  9. It is used for corroded tool repairing.
1920px SLS schematic.svg
LMD used in laser sintering process. 1.Laser 2.Scanner system 3.Powder delivery system 4.Powder delivery piston 5 Roller 6 Fabrication piston 7 Fabrication powder bed 8 Object being fabricated (see inset) A Laser scanning direction B Sintered powder particles (brown state) C Laser beam D Laser sintering E Pre-placed powder bed (green state) F Unsintered material in previous layers. Image source: GringerSLS schematicCC BY-SA 4.0

Flexible features for metal and alloy components in LMD

The process of laser metal deposition or LMD allows to control the power applied beforehand. The metal powder is injected according to the specified power output. This is used for producing custom alloys. Proper material composition can be difficult. If the composition is not accurate, obtaining the required alloy might be difficult. Some common alloys manufactured through this process are iron-tantalum, iron copper, and titanium-tantalum.

Why are CO2 lasers not used for LMD?

Initially, when the process of laser metal deposition was first introduced, CO2 lasers were widely used. Carbon dioxide lasers can produce a very high power continuous beam of IR light with principal wavelength bands ranging from 9.6 to 10.6 micrometers. However, with the development of fiber lasers, the use of CO2 lasers was reduced. These lasers were comparatively costlier and did not allow a controlled flow of laser power.

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