Laser cladding repair technology is a kind of material surface modification technology. It is the use of laser high power density beam, by the laser processing system under the control of numerical control, the matrix surface to form a very thin layer of micro melt layer. Self-fusing alloy powder with specific composition, such as nickel base, cobalt base and iron base alloy, is added in a preset or synchronous way, so that they are evenly spread on the surface of the parts in a molten state and reach a predetermined thickness, forming a good metallurgical bond with the micro-molten base metal material, and there is only a small dilution between each other. In the subsequent solidification process, a functional cladding material layer with predetermined special properties that is completely different from the matrix is formed on the surface of the part, which can completely change the surface properties of the material, and ultimately make the surface of the inexpensive material obtain extremely high wear resistance, corrosion resistance, high temperature resistance and other properties.
According to the different material addition methods, laser cladding methods are divided into preset method and synchronous powder feeding method. As the name implies, the pre-coated material is placed on the pre-treated substrate surface by spraying or bonding, and then remelted by laser beam radiation before appropriate heat treatment; Synchronous powder feeding is to spray the powder directly on the mobile melting pool formed by laser radiation on the surface of the cladding substrate after pretreatment, and the coating is formed at one time. Synchronous powder feeding is the development trend of laser cladding technology, which can make full use of laser energy, control process parameters, improve production efficiency and coating quality. However, synchronous powder delivery also has requirements for the particle size and fluidity of the powder, which need to be determined according to the specific situation.
Laser cladding materials and properties
In the study of laser cladding, material research is an important direction, focusing on the compatibility of various additive materials and parts in practical application scenarios. Iron based alloy powder is suitable for parts that require local wear resistance and are easily deformed. Cobalt-based alloy powder has good high temperature resistance, wear resistance and corrosion resistance, and is often used in petrochemical and metallurgical fields. Ceramic materials have high strength at high temperatures, good thermal stability, high chemical stability, and are often used in parts requiring wear resistance, corrosion resistance, high temperature resistance and oxidation resistance. Because a single material in the case of sliding wear, impact wear and abrasive wear serious will not meet the requirements of the use of conditions. Therefore, the composite use of metal coating and ceramic coating has become a research hotspot, there have been steel, titanium alloy and aluminum alloy surface laser cladding of a variety of ceramic or cermet coating research.
Compared with other traditional surface treatment technologies, laser cladding has its own characteristics and advantages:
The cooling speed is fast (up to 10^6 ° C /s), which belongs to the solidification process, and it is easy to obtain fine crystal structure or produce new phases that can not be obtained in equilibrium state, such as unstable phase and amorphous state. The dilution rate of the coating is less than 5%, and the matrix is firmly bonded by metallurgy or interfacial diffusion, to obtain a good cladding layer with controllable coating composition and dilution degree, and ensure that the performance does not degenerate. With high power density cladding, the heating speed is fast, and the heat input, heat affected zone and distortion of the substrate are small. Powder selection is almost unlimited, and high melting point alloys can be deposited on the surface of low melting point metals. The thickness and hardness range of the cladding layer are large, and the cladding layer has fewer microscopic defects and better performance. The process adopts numerical control, no contact treatment, automatic operation, convenient, flexible, strong controllability.
Typical application of laser cladding in industry
Laser cladding this repair and remanufacturing process, one is to strengthen the function, can enhance the performance of the substrate through the cladding layer; The second is the repair function, which is mainly reflected in the repair of the holes and cracks on the surface of the material, and the restoration of the geometric size and performance of the worn parts, which has very great application value for almost the entire machinery manufacturing industry.
In stone mining, chemical industry, metallurgy, electric power, cement and other mechanical equipment industries, gas turbine rotor journal and blade, rolling roller journal, steel mill arch, etc., will age and damage with the use of time. Due to the long-term exposure of these parts to high temperature and high-pressure gas and corrosive media, coupled with the mechanical stress caused by volume load, most of the damage occurs on the surface or surface, and the failure mode is mainly the fragmentation and cracking of the internal metal parts, wear or corrosion serious to local spalling. Therefore, the application of laser cladding technology to strengthen the surface properties of parts can effectively extend the service life, and in the periodic maintenance process, the damaged parts can also be remedied by surface remanufacturing technology.
Turbine rotor repair
For gas and steam turbines, failure sites often occur in hot-end components such as rotors, blades and nozzles. The fracture occurring at the root of the blade is irreparable, while the damage occurring at the end face or root of the blade can be reused after repair. In addition, the blades used for generating sets are often very expensive, and the re-use of repaired blades will greatly reduce the cost of power generation.
In the automobile manufacturing industry, since the 1980s, countries such as Europe, the United States, Japan, Russia and China have begun to use laser cladding to strengthen auto parts. Through this technology, the purpose of saving expensive alloy materials and reducing production costs is achieved. Similarly, the failure caused by wear, corrosion and contact fatigue of automobile molds in use can also be revitalized by this technology.
In short, whether it is the surface strengthening of the parts before service or the repair of the fault after service, the traditional processing methods mainly include surface quenching, surface carburizing or nitriding, thermal spraying, surfacing welding and so on. With the continuous upgrading and improvement of processing technology, laser mobile remanufacturing technology (laser cladding) has been widely used.
This laser remanufacturing technology can not only be used for the repair of damaged parts, but also for laser surface quenching, compared with the traditional heat treatment, laser quenching is a fast heating and fast cooling processing technology, which can obtain a hardened layer of fine grains on the surface. In addition, combined with high-end multi-axis machine tools or 6+2 robots, the use of lasers can also repair damaged three-dimensional complex parts, fully reflecting the flexibility and advanced nature of laser remanufacturing technology.
Xi'an Guosheng Laser Technology Co., Ltd. is a high-tech enterprise specializing in R&D, manufacturing and sales of automatic laser cladding machine, high-speed laser cladding machine, laser quenching machine, laser welding machine and laser 3D printing equipment. Our products are cost-effective and sold domestically and abroad. If you're interested in our products, please contact us at bob@gshenglaser.com.