Laser remelting is to make the surface of material undergo a rapid melting solidification process, and the resulting fused layer is as cast structure, also known as liquid phase quenching. Laser cladding is to irradiate the surface of materials with laser, add alloy powder at the same time, rapidly melt the alloy powder, and then rapidly solidify to form a dense, uniform and thickness controllable metallurgical bonding layer, so as to achieve the effect of repairing the surface size of workpieces, strengthening and extending the service life. The difference between laser cladding and laser remelting is described below.
The difference between laser cladding and laser remelting is that one is to directly act on the material surface, and the other is to add new alloys on the material surface. The purpose is to improve hardness, wear resistance and corrosion resistance. Reasonable selection should be made according to the actual situation.
Laser cladding technology refers to a process method of placing a selected coating material on the surface of the coated substrate in different filler ways, melting it and a thin layer of the substrate surface at the same time by laser irradiation, and rapidly solidifying it to form a surface coating with extremely low dilution and metallurgical combination with the substrate material, so as to significantly improve the wear resistance, corrosion resistance, heat resistance, oxidation resistance and electrical characteristics of the substrate surface.
Laser cladding has the following characteristics:
(1) The cooling speed is fast (up to 106k / s), which belongs to the rapid solidification process. It is easy to obtain fine crystal structure or generate new phases that cannot be obtained in equilibrium state, such as unstable phase and amorphous phase.
(2) The dilution ratio of the coating is low (generally less than 5%), and it is in solid metallurgical bonding or interface diffusion bonding with the substrate. By adjusting the laser process parameters, a good coating with low dilution ratio can be obtained, and the coating composition and dilution can be controlled;
(3) The heat input and distortion are small, especially when high power density fast cladding is used, the deformation can be reduced to the assembly tolerance of the parts.
(4) There are almost no restrictions on powder selection, especially for depositing high melting point alloys on the surface of low melting point metals;
(5) The thickness of the cladding layer ranges from 0.2 to 2.0mm in a single pass of powder feeding,
(6) Can carry out selective welding, with less material consumption and excellent performance price ratio;
(7) The beam aiming can weld the inaccessible area;
(8) The process is easy to realize automation.
The main features of laser remelting are as follows:
(1) Generally, no alloying elements are added during surface melting, and the fusion layer and the material matrix are natural metallurgical bonding.
(2) In the process of laser melting, impurities and gases can be eliminated, and the microstructure obtained by quenching recrystallization has high hardness, wear resistance and corrosion resistance.
(3) The melting layer is thin and the heat action zone is small, which has little effect on the surface roughness and workpiece size, and can even be used directly.
The above is the difference between laser cladding and laser remelting. Both laser cladding and laser remelting are applicable to industry. With the rapid development of laser technology, it has become a hot spot in the research of laser surface modification at home and abroad. Laser technology has great technical and economic benefits, and is widely used in machinery manufacturing and maintenance, automobile manufacturing, textile machinery, navigation and aerospace.
Source: Wuhan Ruifeng Optoelectronics
