Laser cladding

Laser cladding is a method of depositing material by which a powdered or wire feedstock material is melted and consolidated by use of a laser in order to coat part of a substrate or fabricate a near-net shape part.
Cladding process
The powder used in laser cladding is normally of a metallic nature, and is injected into the system by either coaxial or lateral nozzles. The interaction of the metallic powder stream and the laser causes melting to occur, and is known as the melt pool. This is deposited onto a substrate; moving the substrate allows the melt pool to solidify and thus produces a track of solid metal. This is the most common technique, however some processes involve moving the laser/nozzle assembly over a stationary substrate to produce solidified tracks. The motion of the substrate is guided by a CAD system which interpolates solid objects into a set of tracks, thus producing the desired part at the end of the trajectory.

Uses

* A method of additive manufacturing
* Application of coatings on engineering components surfaces with improved mechanical or corrosion resistance properties
* Repair or resurfacing of worn or damaged parts
* A method of fabricating metal matrix composites

Automation

A great deal of research is now being concentrated on developing automatic laser cladding machines. Many of the process parameters must be manually set, such as laser power, laser focal point, substrate velocity, powder injection rate, etc., and thus require the attention of a specialized technician to ensure proper results. However, many groups are focusing their attention on developing sensors to measure the process online. Such sensors monitor the clad's geometry (height and width of deposited track), metallurgical properties (such as the rate of solidification, and hence the final microstructure), and temperature information of both the immediate melt pool and its surrounding areas. With such sensors, control strategies are being designed such that constant observation from a technician is no longer required to produce a final product.

Injection seeders are devices that direct the output of small "seed" lasers into the cavity of a much larger laser to stabilize the latter's output. Most seed lasers are stable, single-frequency lasers that emit within the linewidth of the larger laser's gain medium. The single frequency encourages the larger laser to lase in a single longitudinal mode, and the seed laser can also improve the laser's spatial profile and improve the M2 parameter. Seed lasers can be continuous or pulsed. Seeding a pulsed laser can reduce variations in the output energy and timing (jitter) from pulse to pulse, and smooth out temporal variations within the pulse. Many commercial lasers use a laser diode as a seeding source.

An Alternative to traditional welding and thermal spray is Laser Cladding. This technology is similar to thermal spray in that it has an energy source to melt the feed stock that is being applied to a substrate. Where it differs is that it uses a concentrated laser beam as the heat source and it melts the substrate that the feed stock is being applied to. This results in a metallurgical bond that has superior bond strength over thermal spray. Additionally the resulting coating is 100% dense with no voids or porosity.

An Alternative to traditional welding and thermal spray is Laser Cladding. This technology is similar to thermal spray in that it has an energy source to melt the feed stock that is being applied to a substrate. Where it differs is that it uses a concentrated laser beam as the heat source and it melts the substrate that the feed stock is being applied to. This results in a metallurgical bond that has superior bond strength over thermal spray. Additionally the resulting coating is 100% dense with no voids or porosity.

The basic system is made up of a laser to generate the beam, a set of optics to direct and focus the beam, a powder feeder, and a part manipulator. The laser and optics stay stationary and the part is moved in relationship to the laser. The laser cladding systems are fully automated providing precise control of the coating (cladding) process.

One of the advantages of the laser cladding process is the concentrated beam of energy from the laser. It can be focused and concentrated to a very small area and keeps the heat effected zone of the substrate very shallow. This minimizes the chance of cracking, distorting, or changing the metallurgy of the substrate. Additionally the lower total heat minimizes the dilution of the coating with material from the substrate.

Coating thicknesses can reach .125" (3.1mm) with carbides in one pass and can go to any thickness with other materials and multiple passes.

Because the feed stock is a powder, there is a large variety of materials available including pure metals, alloys, or carbides. We have worked extensively with Inconel and Stellite alloys on a wide assortment of oil field applications.

A recent addition to our Conroe Texas facility is an inner diameter cladding tool. We now can coat the inside of a tube as small as 2.5 inches to a depth of 36 inches. This has found to be extremely valuable for hard chrome replacement for landing gear with chrome carbide. It is very difficult to thermal spray smaller inside diameters.

Thermal Spray Depot has partnered with Technogenia to provide laser cladding services. Licensing opportunities exist for appropriate applications. Please give us a call to see how we might be able to help you with your coating needs or to find out more about our Conroe, Texas location.lasers use a laser diode as a seeding source.

David Moreno
17812731
CAF