What Are The Applications Of Laser Technology In Surface Treatment?

Laser surface treatment is the use of high-power density laser beam to heat the surface of the material in a non-contact manner. The surface modification technology is realized by the conduction cooling of the material surface itself. It is of great benefit in improving the mechanical and physical properties of the material surface, as well as improving the wear resistance, corrosion resistance and fatigue resistance of the parts. In recent years, laser surface treatment technologies such as laser cleaning, laser quenching, laser alloying, laser shock strengthening, laser annealing, as well as laser cladding, laser 3D printing, laser plating and other laser additive manufacturing technologies have ushered in broad application prospects.

Laser cleaning is a rapidly developing new surface cleaning technology, which uses a high-energy pulsed laser beam to irradiate the surface of the workpiece so that the surface of the dirt, particles or coating instant evaporation or expansion stripping, so as to achieve a clean process. Laser cleaning is mainly divided into rust removal, oil removal, paint removal, coating and other processes; Mainly used in metal cleaning, cultural relics cleaning, building cleaning and so on. Based on its comprehensive functions, precise and flexible processing, high efficiency and energy saving, green environmental protection, no damage to the substrate, intelligence, good cleaning quality, safety, wide range of applications and other characteristics and advantages, it is increasingly popular in various industrial fields.

Compared with traditional cleaning methods such as mechanical friction cleaning, chemical corrosion cleaning, liquid solid strong impact cleaning, high-frequency ultrasonic cleaning, laser cleaning has obvious advantages.

Laser quenching uses the high-energy laser as a heat source to make the metal surface hot and cold quickly, instantly complete the quenching process, obtain high hardness, ultra-fine martensitic structure, improve the hardness and wear resistance of the metal surface, and form compressive stress on the surface to improve fatigue resistance. The core advantages of this process include small heat-affected zone, small deformation, high degree of automation, good flexibility of selective quenching, high hardness of refined grain and intelligent environmental protection. For example, the laser spot can be adjusted to quench the position of any width; Secondly, the laser head is linked with a multi-axis robot to quench the designated area of complex parts. For example, laser quenching is extremely hot and cold, and quenching stress and deformation are small. The deformation of the workpiece before and after laser quenching can be almost ignored, so it is particularly suitable for the surface treatment of parts requiring high precision.

At present, laser hardening has been successfully applied to the surface strengthening of wearing parts in the automotive industry, mold industry, hardware tools, and machinery industry, especially in improving the service life of the gear, shaft surface, guide rail, jaws, molds and other wearing parts, and the effect is remarkable. Laser quenching features are as follows:

1) Laser quenching is rapid heating, self-cooling, and does not require furnace insulation and coolant quenching. It is a pollution-free green environmental protection heat treatment process, which can be easy to implement uniform quenching of large mold surfaces;

2) Because the laser heating speed is fast, the heat affected zone is small, and the surface scanning heating quenching is instantaneous local heating quenching, so the deformation of the treated mold is very small;

3) Due to the small divergence Angle of the laser beam, it has good directivity, and can carry out accurate local quenching of the mold surface through the light guide system;

4) The hardened layer depth of laser surface quenching is generally 0.3 ~ 1.5mm.

Laser annealing refers to the heat treatment process that uses a laser to heat the surface of a material, expose the material to high temperatures for a long period of time, and then slowly cool it. The main purpose of the process is to release stress, increase the ductility and toughness of the material, and produce special microstructure. It can adjust the matrix structure, reduce the hardness, refine the grain and eliminate the internal stress. In recent years, laser annealing technology has also become a new process in the semiconductor processing industry, which can greatly improve the integration of integrated circuits.

Laser shock strengthening technology is a kind of high technology which uses plasma shock wave generated by strong laser beam to improve the anti-fatigue, anti-wear and anti-corrosion ability of metal materials. It has the advantages of no heat affected zone, high energy utilization, high strain rate, strong controllability and remarkable strengthening effect. At the same time, laser shock strengthening has the characteristics of deeper residual compressive stress, better microstructure and surface integrity, better thermal stability and longer life. In recent years, the technology has been rapidly developed, and it is very useful in the fields of aerospace and national defense. In addition, the role of the use of coating is mainly to protect the workpiece from laser burn and enhance the absorption of laser energy, and the commonly used coating materials are black paint and aluminum foil.

Laser shot peening (LP), also known as laser shock strengthening (LSP), is a process applied to the field of surface engineering, that is, the use of pulsed high-power laser beams to create residual stress in a material to improve the damage resistance of the material surface (such as wear resistance and fatigue resistance), or to improve the strength of a material's thin section to strengthen the surface hardness of the material.

Unlike most material processing applications, LSP does not use laser power for heat treatment to achieve the desired results, but instead uses beam impact for machining. High-power laser beam with high-power short pulse impact target workpiece surface.

The beam of light strikes the metal workpiece, instantly vaporizing the workpiece into a thin layer of plasma state and applying shock wave pressure to the workpiece. Sometimes a thin layer of opaque cladding is attached to the workpiece to replace metal evaporation. To pressurize, the plasma (usually water) is captured using other transparent cladding materials or inertial interference layers.

The plasma produces a shock wave effect, reshaping the surface microstructure of the workpiece at the point of impact, which in turn creates a chain reaction of metal expansion and compression. The deep compressive stress generated by this reaction can extend the life of the component.

Laser alloying is a new surface modification technology, which can prepare amorphous single nanocrystalline reinforced cermet composite coating on the surface of structural parts according to the different service conditions of aviation materials by using high energy density laser beam with high heating and condensing rate. Compared with laser alloying technology, laser cladding technology has the characteristics of smaller dilution rate of the substrate to the molten pool, smaller heat-affected zone, smaller thermal deformation of the workpiece and smaller scrap rate of the workpiece after laser cladding treatment. Laser cladding can significantly improve the surface properties of materials, can be repaired for wear failure materials, with high efficiency, fast speed, green environmental protection and no pollution and good performance of the workpiece after treatment.

Laser cladding technology is also one of the new surface modification technologies representing the development direction and level of surface engineering. Laser cladding technology has become a hot spot in the study of surface modification of titanium alloys due to its advantages of no pollution and metallurgical bonding between the coating and the substrate. Laser cladding ceramic coating or ceramic particle reinforced composite coating is an effective way to improve the surface wear resistance of titanium alloys. According to the actual working conditions, the appropriate material system is selected, and the best process requirements can be achieved by laser cladding technology. Laser cladding technology can repair various failed parts, such as aero engine blades.

The difference between laser surface alloying and laser surface cladding is that the alloying layer is formed by mixing the added alloying elements and the substrate surface in liquid state. The laser surface cladding is to melt all the precoating and melt the surface of the substrate, so that the cladding layer and the substrate material form a metallurgical combination and keep the composition of the cladding layer basically unchanged. Laser alloying and laser cladding technology are mainly used to improve the surface wear resistance, corrosion resistance and grade resistance of titanium alloys.

At present, laser cladding technology has been widely used in the repair and modification of metal surfaces, but although the traditional laser cladding has the advantages and characteristics of flexible processing, shaped repair, custom additive, etc., the working efficiency is low, and the large-scale and rapid production and processing needs required in some production fields can not be met. In order to meet the demand of high volume and high-speed production and improve the cladding efficiency, high-speed laser cladding technology came into being.

Laser engraving processing is the use of numerical control technology as the basis, the high energy laser beam projected onto the surface of the material, the use of laser thermal effect, the surface of the material to produce a clear pattern of laser processing process. The physical deformation of the processing material in the instant melting and gasification under the irradiation of laser engraving can make laser engraving realize the processing purpose. Laser engraving is the use of laser to write words on the object, this technology carved out the word without marks, the surface of the object is smooth and flat, the writing will not wear. Its features and advantages include: safe and reliability; Precise and fine, the accuracy can reach 0.02mm; Saves environmental protection, processing save materials; High speed, high-speed engraving according to the output pattern; Low cost, not limited by the number of processing.

The process uses laser cladding technology, the use of laser irradiation nozzle conveying powder flow, directly melt the elemental or alloy powder, after the laser beam left, the alloy liquid quickly solidifies, to achieve rapid alloy molding. At present, it has been widely used in industrial modeling, machinery manufacturing, aerospace, military, architecture, film and television, home appliances, light industry, medicine, archaeology, culture and art, sculpture, jewelry and other fields.

At present, laser surface treatment and additive manufacturing technology, process and equipment are widely used in metallurgy, mining machinery, mold, petroleum power, hardware tools, rail transportation, aerospace, machinery and other industries.

Laser electroplating is a new high-energy beam electroplating technology, which is of great significance to the production and repair of microelectronic devices and large-scale integrated circuits. At present, although the principles of laser plating, laser ablation, plasma laser deposition and laser injection are still under research, the technology is already in use. When a continuous laser or pulsed laser is irradiated on the cathode surface of the electroplating pool, not only the deposition rate of the metal can be greatly improved, but also the non-shielded coating with the expected complex geometry can be obtained by controlling the trajectory of the laser beam by computer.

Compared with ordinary electroplating, its advantages are:

(1) The deposition speed is fast, such as laser gold plating up to 1μm/s, laser copper plating up to 10μm/s, laser jet gold plating up to 12μm/s, laser jet copper plating up to 50μm/s;

(2) The metal deposition only occurs in the laser irradiation area, and the local deposition coating can be obtained without using shielding measures, thus simplifying the production process;

(3) the binding force of the coating is greatly improved;

(4) Easy to achieve automatic control;

(5) Save precious metals;

(6) Save equipment investment and processing time.

Xi'an Guosheng Laser Technology Co., Ltd. is a high-tech enterprise specializing in R&D, manufacturing and sales of automatic laser cladding machine, high-speed laser cladding machine, laser quenching machine, laser welding machine and laser 3D printing equipment. Our products are cost-effective and sold domestically and abroad. If you're interested in our products, please contact us at bob@gshenglaser.com.