Application of Laser Cladding Technology in Port Machinery Maintenance

1.Laser cladding technology

1.1 The principle of laser cladding
Laser cladding technology is based on different filling methods, placing the selected alloy material on the surface of the cladding substrate, irradiating it with a high-energy laser beam, and rapidly melting, expanding, and condensing a thin layer on the surface of the substrate at the same time to form The dilution rate is very low (generally less than 5%), and the surface coating of the alloy is formed with the base material to improve the technical process of the metal surface’s wear resistance, corrosion resistance, high temperature resistance and oxidation resistance.
1.2  Characteristics of laser cladding
Compared with traditional processes such as electroplating, spraying, surfacing welding and vapor deposition, the advantages of laser cladding technology are:
(1) The structure of the cladding layer is uniform and compact, with few micro-defects, high bonding strength with the base material, and good controllability of the dilution rate.
(2) The laser energy density is high, the action time is short, the cooling rate is fast, the tissue has the characteristics of rapid condensation, the heat-affected zone of the substrate is small, and the thermal deformation is small.
(3) Laser cladding is non-contact processing, which is easy to realize automation and can carry out selective cladding.
(4) The cladding thickness is controllable, and the cladding can be in the range of 0.2 to 2.0 mm in a single pass.
(5) The laser cladding layer has high hardness and good toughness, and the service life of the workpiece can be increased by 5 to 8 times.
(6) It has the characteristics of energy saving and environmental protection.
1.3 repairable basic materials and cladding materials
Laser cladding technology can repair low carbon steel, medium carbon steel and various alloy steels, stainless steel, cast iron, copper and copper alloys, aluminum and aluminum alloys, etc.
According to the different performance requirements of the substrate, iron-based, nickel-based, cobalt-based self-fluxing powders and composite powders with different compositions can be selected. The choice of laser cladding powder is a key factor in determining the quality and performance of the laser cladding layer. The iron-based powders mainly include: Fe30, Fe45, Fe60, etc. Nickel-based powders mainly include: Ni20, Ni25A, Ni45, Ni60, etc. Cobalt-based powders mainly include: Co42A, Co42B, Co42C, Co50, etc. The powder has good flexibility, self-melting, wettability and cladding properties.
1.4 The relationship between excellent performance of laser cladding layer and microstructure
At the bottom of the cladding layer, the structure is a typical dendritic crystal growing in the direction of heat flow. There is a narrow white bright band on the surface of the cladding layer and the substrate. The structure is flat crystal, showing metallurgical bonding characteristics and high bonding strength.
The rapid solidification of the laser cladding process can obtain a good dendritic microstructure, compact structure, and in-situ generated dangerous particle-enhancing particles, such as carbon, silicide or silicide, are dispersed in the dendrites, which can achieve particle dispersion strengthening and Refinement strengthening effect. At the same time, the rapid cooling conditions far away from the equilibrium state under high temperature gradient are the formation of a large amount of supersaturated solid solution in the solidification structure, and the crystal lattice is deformed. Therefore, the cladding layer has high hardness, good wear resistance, corrosion resistance, high temperature resistance, and oxidation resistance. And other comprehensive performance.

2.Application of laser cladding technology

The drive part of modern port machinery is composed of high-power motors, gearboxes, etc. Due to factors such as long uninterrupted use of the equipment and harsh working environment, various parts of the motor and gearbox will experience varying degrees of wear after long-term operation. Seriously, it will affect the normal use of the equipment.
The transmission part of the gearbox is damaged by local friction, especially the inner hole of the housing at the contact surface of the bearing and the housing is a part that is easy to wear. Improper handling will cause the entire gearbox to be scrapped.
2.1 The application of laser cladding technology in the maintenance of motor rotor shaft
The rotor shaft of the motor is the core component of the motor, which carries the size coordination and installation between the components of the motor. The rotor shaft is usually worn and impacted severely during the working process.
The laser cladding technology is used to repair and rebuild the crisis of the rotor shaft shaft end and the bearing chamber. The laser cladding layer and the substrate are metallurgically combined. At the same time, the cladding material can be better selected to fill larger groove marks, pits, holes and other defects , It is suitable for shafts with large deformation, and the hardness of the cladding layer can reach HRC5 or higher, which is incomparable to the traditional maintenance techniques such as brush plating, spraying and surfacing welding. Most of the motors in port machinery equipment are high-power motors, which are expensive and difficult to repair. The use of laser cladding technology can repair the motor shaft, which can effectively reduce maintenance costs.
2.2 The application of laser cladding technology in the repair of gearbox shaft
After a long-term high-load operation of the gearbox, its high-speed shaft and low-speed shaft will wear out, produce grooves, and poorly cooperate with the sealing ring, resulting in oil leakage. Repairing the groove of the gearbox shaft through laser fusion technology and replacing the new oil seal at the same time can better solve the problem of oil leakage at the shaft end of the gearbox.
2.3 The application of laser cladding technology in the repair of the shaft hole of the reduction box
Using laser cladding technology, select powder with abrasion resistance much higher than the base material to repair the worn surface of the inner hole of the gearbox housing. After the damaged part is restored to the original design size, the hardness is above HRC55, and the cladding layer and the substrate For metallurgical bonding, the bonding strength is high, which can greatly improve the wear resistance of the inner hole surface, making the service life 5-6 times that of the traditional repair process, which far exceeds the technical indicators of the original new parts.
Process method, environmental protection, bonding method, bonding strength/MPa thickness/mm, laser cladding, green environmental protection, metallurgical bonding, 600-800 single layer, 0.2-1.5, brush plating, producing electroplating wastewater containing heavy metal ions, and isolating acid mist. Waste mechanical bonding is easy to fall off 8-12≤0.5

3. Conclusion

In the application of port machinery in China, steel-based metal materials dominate. At the same time, the failure of metal materials (such as corrosion, wear, fatigue, etc.) mostly occurs on the working surface of the parts, and the surface needs to be strengthened. In order to meet the service conditions of the workpiece, the large in-situ in-situ particle reinforced steel-based composite material is used to manufacture, not only a waste of materials, but also high cost. On the other hand, from the perspective of bionics, the composition of natural biomaterials is dense outside and sparse inside, and the performance is hard outside and tough inside, and the density-sparse, hard-toughness changes gradually from the outside to the inside. The special structure makes it have excellent performance. According to the special service conditions and performance requirements of engineering materials, there is an urgent need to develop a new type of surface metal matrix composite material with strong and tough combination and performance gradient changes. Therefore, the use of laser cladding methods to prepare in-situ functionally gradient in-situ particle-reinforced metal matrix composites that are metallurgically combined with the substrate is not only an urgent need for engineering practice, but also an inevitable trend in the development of laser surface modification technology.

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