Laser surfacing

Modern equipment for laser surfacing is mainly equipped with diode or fiber-optic laser sources. In addition, there are gas and other sources also used for surfacing. Diode lasers are most suitable for the surfacing process, as the energy distribution density at the focal point is most uniform.

Laser surfacing by the nature of the radiation is:

1. Cw laser
2. Pulsed laser

There is wire and powder laser surfacing. Laser scanning of a precoated surface is called laser fusion.

The following feed methods are available:

• Coaxial
• Radial
• Lateral

For laser surfacing, the types of lasers that generate a wavelength in the range of 0.9-1.3 μm are applicable, because in this range, for most pure metals and alloys, the degree of adsorption of radiation is optimal.

1. Fiber optic
2. Diode lasers
3. Alloy Yttrium (YB: YAG)

Continuous Laser Surfacing

Continuous surfacing is characterized by greater productivity. The minimal heat input of laser cladding before other technologies of cladding and welding allows processing even hard-to-weld materials. The average value of the mixing zone of the surfacing material with the base is 10-30 microns, depending on the surfacing conditions. Deposition thickness in one pass varies from 0.3-3 mm.

Today, there are optical systems that allow surfacing both external and internal surfaces. The fundamental difference between systems for internal surfacing is the presence of a prism or mirrors that turn the flow of light energy.

The main consumers of laser surfacing technologies are: oil and gas industry, metallurgy, shipbuilding, gypsum cement ^[1] industry.

Pulse Laser Surfacing

A pulsed laser is characterized by a large peak power; surfacing is done manually, mainly by wire, or using robotic systems (wire or powder). The material is fed into the molten bath.

With manual surfacing, observing the process under a microscope with an increase of 10-16 times. In the eyepiece of the microscope there is a crosshair along which the laser beam is exposed, so the operator always knows where the next pulse will go. The used diameters of the focused laser beam varies from 0.2 - 2.5 mm, depending on the diameter of the filler (d spots should be 1.5-2 times the diameter of the filler, to mix the filler with the surfaced surface), which allows minimize the volume of the melt and, accordingly, reduce heat input into the processed material. An inert gas is supplied to the surfacing zone, which protects the molten bath from oxygen access. Manual surfacing is mainly used to obtain the initial dimensions of worn or damaged parts. Most often used to repair damaged parts of machines and molds. Since the process is essentially welding with an additive, surfacing occurs during the welding of some parts.

Robotic impulse surfacing is often used for new products, as allows you to reduce the cracking of the deposited layer, due to the reduction of thermal effects on the part.

• Dosed energy;
• Possibility of local surface treatment;
• Lack of thermal leash, minimization of the zone of thermal influence;
• the ability to process large-sized parts with a large consumption of deposited substance;
• Fast heating and cooling of the deposited material;
• Possibility of surface modification;
• High adhesion of the deposited material with little mixing with the base ..

Laser surfacing is widespread in industry. The most famous applications are the restoration of damaged surfaces of various machine parts, molds and dies. The second application is surface modification. Additive materials may differ in chemical composition from the base and have other properties. In this way, the worn-out edges of the dies are strengthened by fusing harder material. A newer application is the prototyping of parts. For example, a 3d printer that prints with metal powder essentially fuses the powder layers together.

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