Application of Laser Cladding for Wind Power Parts

Laser Cladding is a surface modification technology, also known as laser metal deposition. It means that the selected coating material is placed on the surface of the cladding substrate in different ways. The substrate is irradiated by laser to melt, and a thin layer of powder composition would solidify rapidly to form metallurgy with the substrate with a very low dilution rate. The combined surface coating significantly improves the wear resistance, corrosion resistance, heat resistance, oxidation resistance, and electrical characteristics of the base layer, to achieve the purpose of surface modification or repair, which not only meets the requirements for specific properties of the material surface, also saves a lot of money to replace the worn parts with new ones.

Robot Laser cladding has the advantage of low dilution rate, compact structure, good combination of coating and substrate, and reliable use. As far as the application of laser cladding is concerned, it is mainly used in three aspects: 1: surface modification of materials, such as steam turbine blades, rolls, etc.; 2: repairing parts, such as wind power main shafts, planet carriers, planetary wheels, etc.; 3: rapid prototyping, that is, the use of metal powder sintering and stacking layer by layer to quickly create a model. Today, we will talk about laser cladding technology in the repair of wind power parts. Figure 1 shows the use of laser cladding to repair the planet carrier journal.

Wind power parts such as spindles and turrets are often found to be rough or severely worn during the maintenance process. If they are not repaired, they cannot be used. Before the laser cladding method is used for repair, most of the parts are treated as scrap. With the advent of laser cladding, we began to repair the inner hole of the planetary gear for the first time. After this special repair technology was adopted, it greatly improves the secondary utilization of parts, reduces the maintenance cost, and shortens the gearbox maintenance cycle.

Ultra-high-speed laser cladding repair can achieve high-efficiency cladding of 0.8-1.2m²/hr (depending on the coating thickness) to achieve the surface coating of spindles and turrets, with a single-layer cladding thickness of 0.05-1mm. Due to the small heat input during the cladding process and the small thermal impact on the workpiece, thin-walled or large aspect ratio parts that cannot be applied by conventional laser cladding can be processed without deformation. According to different customer application requirements, hard wear-resistant coatings of different materials such as cobalt-based, nickel-based, and composite materials can be deposited on the surface of the parts. The maximum hardness of the coating can reach HRC65 or more, and effectively realize crack control. The process of repairing parts by laser cladding is simple and reliable, with the following processes:

1. Removal of the fatigue layer at the repair position of the part, generally requires local grinding or turning. This process has no special requirements for the surface roughness of the part;

2. Carry out pre-heat treatment according to the material characteristics of the parts to prevent defects such as cracks;

3. Laser cladding on the preheated parts, generally with a cladding thickness of 3~4mm, if the hardness of the repair position is higher, the cladding thickness may be relatively reduced, because the thicker the cladding layer, the higher the hardness. Without heat treatment, large-area cladding is prone to cracks and other defects.

4. After cladding, stress relief annealing should be carried out and coloring flaw detection to ensure that the parts are free of defects.

5. Machining the cladding layer to meet the drawing size requirements.