Laser cladding is a surface modification technique. It uses high-energy laser as heat source and alloy powder as welding material. The laser and alloy powder act simultaneously on the metal surface to rapidly melt to form a molten pool, and then rapidly solidify to form a dense, uniform and controllable metallurgical bonding layer. Laser cladding technology can significantly improve the wear resistance, corrosion resistance, heat resistance, oxidation resistance and other properties of metal surfaces.
Laser cladding technology is a complex physical and chemical metallurgical process. When changing the properties of the metal surface, the setting of the laser parameters has a great influence on the quality of the cladding layer. In addition to this, the choice of alloy powder is also an important factor.
Laser cladding alloy powder is mainly divided into self-fluxing alloy powder, composite powder and ceramic powder according to the material composition. Self-fluxing alloy powders can be divided into iron-based (Fe), nickel-based (Ni), and cobalt-based (Co) alloy powders. Its main feature is that it contains boron and silicon, so it has self-deoxidation and slag-forming properties; it also contains high chromium, so it has excellent corrosion resistance and oxidation resistance. Therefore, it has good adaptability to various substrates such as carbon steel, stainless steel, alloy steel, and cast steel, and can obtain a cladding layer with low oxide content and small porosity.Next, Senfeng Laser will introduce you the role of several powders in changing the surface properties of metals
01 Iron base (Fe)
The biggest advantages of iron-based self-fluxing alloy powder are wide material sources, low cost and good wear resistance. The disadvantage is that the melting point is high, the oxidation resistance is poor, the cladding layer is easy to crack, and it is easy to generate pores. In the iron-based alloy powder composition, the hardness of the coating is adjusted by adjusting the content of alloying elements. And by adding other elements to improve the hardness, cracking sensitivity and residual austenite content of the cladding layer, so as to improve the wear resistance and toughness of the cladding layer.
02 Nickel base (Ni)
Under the conditions of severe sliding, impact wear and abrasive wear, pure nickel-based (Ni) self-fluxing alloy powder is no longer suitable for use. At this time, various high melting point carbide, nitride, boride and oxide ceramic particles can be added to the self-fluxing alloy powder to form a metal composite cladding layer.
03 Cobalt base (Co)
Cobalt-based (Co) self-fluxing alloy powder has excellent heat resistance, corrosion resistance, wear resistance, impact resistance and high temperature oxidation resistance, and is often used in petrochemical, electric power, metallurgy and other industrial fields. At present, the alloying elements used in cobalt-based alloys are mainly nickel, carbon, chromium and iron. Among them, nickel element can reduce the thermal expansion coefficient of the cobalt-based alloy cladding layer, reduce the melting temperature range of the alloy, effectively prevent cracks in the cladding layer, and improve the wettability of the cladding alloy to the substrate.
By cladding the alloy powder on the surface of the workpiece by laser, a high-performance alloy surface can be prepared on a cheap metal substrate without affecting the properties of the substrate, effectively reducing the production cost and saving precious and rare metal materials. Compared with traditional surface treatment technologies such as surfacing, thermal spraying, and electroplating, laser cladding has the advantages of small dilution, dense structure, good combination of coating and substrate, more suitable cladding materials, high processing quality, and good controllability.
At present, laser cladding is mainly used for material surface modification (such as hydraulic columns, rolls, gears, gas turbine blades, etc.), and product surface repair (such as rotors, molds, bearing inner holes, etc. that fail due to wear). The strength of the repaired parts can reach more than 90% of the original strength, and the repair cost is less than 1/5 of the replacement cost of the product. More importantly, the repair time is shortened, which effectively solves the problem of rapid repair of the rotating parts of major complete sets of equipment in large enterprises. .
In addition, laser cladding can greatly improve the service life of parts without deforming the surface of the parts. Laser cladding treatment on the mold surface not only improves the strength of the mold, but also reduces the manufacturing cost by 2/3 and shortens the manufacturing cycle by 4/5.If you want to learn more about laser cladding, please contact SENFENG.
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