Laser cladding is a kind of remanufacturing craft that uses high-energy laser beam to clad a metallurgical bonded cladding layer featuring high hardness and good heat stability on metal surface.
Due to rapid heating caused by high energy density of laser beam, the laser cladding has tiny thermal effect on base materials and gives rise to small deformation. Controlling the laser input energy can also put dilution effect on the base materials at a very low level, resulting in the excellence of original materials.
Laser cladding can clad high-melting materials on the surface of low-melting base materials. In view of material composition free from metallurgical thermodynamics, a wide range of materials are available, such as, nickel-, iron- and cobalt-base alloy, carbide composite alloy, ceramic materials, therein, alloy materials and carbide composites have been put into practical use by reason of their long-term development.
Arresting Pros
- Highly-dense coating with no crack
- Less heat input and subsequent processing quantity, less and controllable workpiece deformation, as well as small heat-affected area.
- Low dilution rate and superior cladding effects due to small changes of alloy composition when base materials melt into the cladding layer.
- Take good control of cladding layer thickness.
- Fast cooling and rapid solidification. It is easy to gain fine-grained microstructures or generate new phases like unstable phase or amorphous state unavailable in equilibrium state.
- Almost no limit to choose powders, especially while cladding high-melting alloy on the surface of low-melting metals.
- Clad on designated partitions available, with less consumption but high cost performance.
- Long service life, namely, over 5 times of common base materials in terms of corrosion resistance.
As for cons, the cladding layer is shallow in thickness, because it is only suitable for repairing and reinforcing the relatively shallow surface compared with traditional modes like build-up welding; high in unit price, in comparison with other traditional surface treatment modes including electroplating, thermal spraying and built-up welding; unsound in occupation standards or no identical norms when using powders and workmanship required by laser cladding as a result of its short term of development.
For the time being, the quality of laser cladding layer depends on:
I. the cladding path shape, surface flatness, crack, air hole, dilution rate at a macro level;
II. at a micro level, the state of microstructures and whether performance as required is feasible. If needed, lifespan of cladding layer may also be detected.
Considering that laser cladding stands for rapid melting and fast solidification, it is feasible to inhibit its composition segregation by adjusting interaction time between laser and cladding metals or changing technological parameters including molten pool convection by means of laser beam type adjustment, so as to obtain the well-formed cladding layer and take control of its internal stress. As a result, the designed performance of cladding layer will be highly satisfied.
As current science and technology is constantly developing, we believe that laser cladding will surely hold much greater prospects. Exploring directions next will be the continual upgrade of laser cladding machines, further optimization of cladding crafts, as well as research and development of material system more fit for laser cladding.
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