What Kinds Of Laser Surface Treatment Are There?

After the appearance of the laser, the design and modification of materials and workpiece surface with laser, are very exquisite. The traditional surface treatment of metal materials has been studied for a long time, but the operation is clumsy and dirty, and the performance control is too rough. And the use of a laser beam quickly, a local heating workpiece, to achieve local urgent heating or cooling, can be processed in the atmosphere, vacuum, and other environments. The surface treatment technology of different materials can be solved by changing laser parameters. The workpiece deformation is very small and is a non-contact processing method. It is divided into surface modification treatment (including laser glazing, laser remelting, laser alloying, laser coating), laser modification treatment, and laser removal treatment (such as laser cleaning) according to the purpose of surface treatment.

I. Laser marking and laser surface coating

1. Laser marking technology is one of the largest application fields in laser processing. There are now laser marking devices on the market for a wide variety of materials. Laser marking lasers are usually near-infrared and use rapid pulses to create visible marks on the surface of the material. Both the depth and the pattern of the marking can be controlled by a computer. For example, marking on the surface of different metals, marking on glass, marking on optical fiber, and different materials marking pulse width, pulse speed, and temperature level have corresponding standards.

2. Laser surface woolens treatment. The laser continuous wave is not easy to control the material surface woolen, the surface woolen looks like intensive marking is easy to control, according to different requirements, and can be used as a millisecond pulse, picosecond pulse, or femtosecond pulse () can achieve better construction effect.

In the material surface wool processing, it is worth mentioning how to solve the cold rolled steel plate surface rough or pattern requirements, so people also have these requirements for the surface of the cold rolling roll, but also require the long service life of the roll. The best processing method is to apply laser pulse wool treatment to the roll.

The processing process is roughly like this: with thousands to tens of thousands of times per second pulse laser beam focusing on the surface of the roll, in the focal point of the roll surface to form a small solubilization pool, at the same time on the micro solubilization poolside blowing, so that the melt in the solubilization pool as far as possible to accumulate to the edge of the solubilization pool to form a circular arc convex, the surface of these small convex and micro pit is strengthened and hardened.

This method of laser wool treatment of role brings a lot of construction convenience for the process of the rolling sheet.

Surface coating of cold rolled sheet and strip materials is widely used. For a simple example, to paint a car panel, the surface of the sheet must be evenly distributed with "pits" to enhance the adhesion of the paint, so the car panel is specially rolled. Cold-rolled strips are used in large quantities in industries such as automotive, construction, home appliances and electronics, light industry, and national defense.

Ⅱ.Laser surface modification treatment

1. Laser surface phase change hardening treatment

Metal material surface hardening is to achieve "quenching" on the surface of the material, the general means is difficult to do, but, with laser hardening material surface is very easy. As needed, hardening can be required to produce phase changes on the surface of the material.

A laser is used to melt the surface of a material quickly, and when the laser beam leaves it solidifies quickly. This is a kind of self-quenching, where a phase transition occurs in the shallower layer of tissue on the surface of the material. The surface of the material contains tiny crystals, which harden the surface.

2. Laser surface alloying treatment

A technique that uses lasers to heat the surface of a local area of a material to a certain temperature or to form a thin melting layer, changing the chemical composition of the surface by diffusion or adding alloying elements or chemical reactions to improve the mechanical, physical and chemical properties of the material surface. It has the advantages of local processing, low matrix deformation, no damage to matrix properties, high efficiency, and rapid heating. It is especially suitable for the important parts of the workpiece, such as the mold seam line, valve tappet, and the local surface of the camshaft.

Laser surface alloying not only improves the "bottleneck" part of workpiece life but also reduces the process and saves alloying elements.

3. Laser surface coating treatment

Laser coating is similar to laser alloying in that some other alloy material is fused into the matrix while the laser is heating it.

In addition to the metallurgical bonding between the matrix and the melted coating material, the coating material is seldom diluted by the matrix material and basically keeps its original composition unchanged.

Compared with laser alloying, laser coating can better control the composition and thickness of the surface layer, and can obtain the surface alloy layer completely different from the substrate, so as to achieve the purpose of wear resistance and corrosion resistance.

4. Laser cleaning

The use of high-energy laser beam irradiation workpiece surface, so that the surface of the dirt, rust, or coating instantaneous evaporation or peeling, high speed and effective removal of surface pollutants or coatings. Laser cleaning belongs to dry cleaning, does not need organic solvents, no waste liquid emissions, and less residue, will not cause environmental pollution, and can effectively remove other methods difficult to remove clean adsorption on the surface of the submicron particles. The technology has high flexibility, good controllability, easy-to-select positioning precision cleaning, easy to remote control cleaning difficult to reach or dangerous places.

There are generally 4 methods of laser cleaning:

(1)Laser dry cleaning method, that is, the use of pulsed laser direct radiation decontamination;

(2) Laser + liquid film method, that is, first deposit a layer of liquid film on the surface of the substrate, and then use a laser to make the liquid film explosion decontamination;

(3) Laser + inert gas method, that is, at the same time of laser radiation, with inert gas blowing to the workpiece surface, when the dirt is peeled from the surface, the gas is far away from the surface, to avoid clean surface pollution and oxidation;

(4) Use the laser to loosen the dirt, and then use non-corrosive chemical methods to decontaminate.

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