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Laser cladding, also known as laser cladding or laser cladding, laser irradiation and laser remelting, are directly treated with matrix material without the addition of other materials, but laser cladding is achieved by adding a clad material to the substrate surface and using high Energy density of the blue laser pointer beam, so that with the substrate surface layer of the method of melting together, in the formation of the base layer with its metallurgical combination of filler cladding.

Laser cladding surface nano-technology can be divided into three main aspects, the first aspect is the use of similar laser remelting surface nano-method, take appropriate measures directly in the laser cladding process to make the deposited layer of nanocrystalline structure. There are two types of this method, one is the melting material and the substrate composition is basically unchanged, the formation of laser cladding pool and the formation of cooling to the main physical process, this method is currently relatively rare literature. The other is in the laser cladding process between the melt and the substrate, or between the welding material and the deposition of chemical reaction between the formation of nano-particles or nano-size organization.

Laser shock peening (LSP) is a kind of high and new technology to improve the fatigue, wear resistance and corrosion resistance of metal materials by using plasma shock wave produced by most powerful laser beams. The impact of laser surface nanocrystallization technology as shown in Figure 6, when the short pulse (NS) high power density (GW/cm2) of the laser irradiation to the metal surface absorption layer, absorbing layer to absorb laser energy explosive vaporization, high pressure (GPa) plasma, the plasma is constrained layer constraint, produce high impact wave effect on the metal surface and to the internal communication, the formation of dislocation structure dense and stable on the surface of the material, plastic deformation by dislocation slip, and the shock wave at the grain boundary reflection and refraction, the shock wave in multi direction effect on grain, thus the complexity of the dislocation slip, agglomeration and annihilation after the formation of new grain boundary, sub grain formation and smaller nanocrystals.

Researchers at the University of Rochester in New York have developed an extraordinary new surface material by bombarding ordinary metals with femtosecond 300mw laser pointer pulses, which can effectively absorb light, water and self-purification. Through the super-laser pulse in the metal surface etching a large number of naked eye, such as pits, beads and fine lines and other "traces", these traces of the formation of dense distribution and uneven nano-microstructure. This nanostructure fundamentally changes the optical properties and wetting properties of the metal surface.

The application of surface treatment technology has a long history, but the surface engineering technology from concept to become a complete system of time subject to, but now only a few decades, laser surface nanocrystallization technology of laser technology and nanotechnology and surface engineering technology combined or can also be called laser nano surface engineering technology.

Although the use of a variety of laser surface treatment technology, such as laser irradiation, laser remelting, laser cladding and 100mw laser pointer shock, has a lot of research materials and achieved fruitful results, but specifically targeted for the use of these technologies, The research on surface nanocrystallization is still relatively small and not systematic, and the development of nano-patterning of laser surface is still in the early stage, so there is still a lot of research work in this field.
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