Laser cladding, also known as laser cladding or laser cladding, a new surface modification technology. It does this by adding the substrate surface of the cladding material, and the use of high-energy density laser beam so that the substrate surface with the method of thin fused together, with the substrate surface material for the metallurgical bonding of the cladding layer Tim.
Because of the high-energy density laser beam generated by the rapid heating process adiabatic approximation, the thermal laser cladding less impact on the substrate, causing the deformation is also small. Control the laser input energy, Zinc oxide but also limit the dilution of the substrate at a very low level (typically 2% to 8%), thus maintaining the high performance of the original cladding material.
Laser cladding cladding material can be in the low melting point melting point of the substrate surface, and material composition of metallurgical thermodynamics are not subject to the usual conditions, the cladding material used in the range is quite extensive, Titanium dioxide including nickel-based , cobalt, iron-based alloy, carbide alloy composite materials and ceramic materials, including alloy material
Carbide composite material and the laser cladding is more mature and practical application has been received. 1, commonly used laser cladding materials.
At present, the laser cladding materials are mainly used thermal spray welding or thermal spraying type of material, its type, including self-fluxing alloy, carbide dispersion or composite materials, ceramic materials.
Such material has excellent wear and corrosion resistance and other properties, usually in powder form to use, and the use of flame spray methods such as cladding, get a smooth surface and with a good coating with the substrate, has been widely used in machinery, metallurgy, electricity, water, air, paper and glass industries. Be used as laser cladding materials can also obtain more satisfactory results, especially the self-fluxing alloy powder, dispersion or self-fluxing carbide composite powders.
(1) self-fluxing alloy powder.
Self-fluxing nickel-base alloy powder can be divided into self-fluxing alloy, cobalt-based self-fluxing alloy, iron-based self-fluxing alloy, whose main characteristic is containing boron and silicon, which has self-performance oxygen and slag, the so-called self-fluxing .
Remelting these alloys, the alloy of boron and silicon is oxidized, Magnesia in the coating film formed on the surface. This film can prevent oxidation of the alloy elements, but also with the formation of oxides of these elements boron silicate slag, resulting in low oxide content, porosity less spray layer. Boron and silicon also reduces the melting point alloy to increase the infiltration of the alloy effect on the alloy surface tension of liquidity and a favorable impact. Self-fluxing alloy hardness and the amount of boron and carbon into the area, with the boron, carbon content increased with the increase, which is due to boron and carbon and alloy of nickel, chromium and other elements to form borides and high hardness increase in the number of carbide.
As the substrate with higher chromium and other elements, so the alloy also has excellent corrosion and oxidation resistance.
To improve the self-fluxing alloy hardness and wear resistance, which can also be adding more in the WC, and WC to form self-fluxing mixture.
(2) carbide composite powder.
Carbide composite powder hard carbide phase by the metal or alloy as the binder phase consisting of powder systems. This type of powder in the binder phase to a certain extent, the carbon from the oxidation and decomposition, Nickel oxide especially by pre-alloyed carbide composite powder can be obtained with a carbide coating performance.
(3) self-bonding composite powder.
Self-adhesive composite thermal spray powder is in the process, due to the exothermic reaction can produce powder coating and the substrate surface to form a good combination of a class of thermal spray materials, its biggest feature is a working flour and backing powder The dual function.
(4) ceramic oxide powder.
Oxide ceramic powder with excellent resistance to high temperature oxidation, Neodymium fluoride as well as heat, wear, corrosion and other properties, is an important class of thermal spray materials, is currently the most attention of the laser cladding materials. Such ceramic powder consists of alumina, zirconia two series, in which zirconia than alumina ceramics powder ceramic powder with a lower thermal conductivity and better thermal shock resistance, which mainly used as heat barrier layer materials. 2, the laser cladding process.
Pre-laser cladding cladding material is placed on the substrate surface of the cladding prior position, Barium titanate and then melted by laser beam scanning irradiation, cladding materials to powder, wire, plate in the form of join, which is most commonly used form of powder .
Synchronized laser cladding cladding material sucked directly into the laser beam, so that for the materials and cladding simultaneously. Cladding material is largely in the form of powder into, and some also used to synchronize wire or sheet feeding.
The main pre-laser cladding process: the substrate surface pretreatment --- preset cladding cladding material laser melting --- --- --- After warm-up heat.
The main synchronization laser cladding process: substrate cladding surface pretreatment --- --- feeding the heat treatment after laser melting. By process, with the laser cladding process is mainly related to the substrate surface preparation methods, cladding materials, feeding method, preheat and post heat treatment.