High-speed laser cladding is a fast laser surface treatment technology. Its process characteristics are good cladding quality, high speed, low cost, and certain market competitive advantages. Improper selection of process parameters for high-speed laser cladding will lead to poor forming quality and easy deformation.
The key parameters involved in the process of high-speed laser cladding are called processing parameters, which directly affect the effect and forming quality of laser cladding. For example, laser power, spot shape, spot size, processing distance, etc., will affect the morphology and quality of the cladding layer. The following describes the eight processing parameters involved in the high-speed laser cladding process.
1. Laser power: the energy output by the laser in unit time. High-speed laser cladding generally uses KW grade lasers, such as LT-3KW, LT-4KW, etc., which are widely used in the market and can meet the needs of most fields.
2. Spot shape: The spot shape is an important factor affecting the cladding quality, and the spot shape is determined by the optical system of the laser. After the laser beam is emitted from the powder feeder, it passes through the scanning system and then to the substrate, forming different light spots at different positions. The shape of light spot directly affects the cladding effect and forming quality. The common spot shapes are divided into two types: circular and rectangular. Users can choose to use them according to the characteristics of the processing object.
3. Spot size: The spot size refers to the area of the light beam scanned to the substrate surface. In the process of laser cladding, the laser energy first concentrates in the center of the cladding layer, and then radiates to the surrounding through radiation. The size of the light spot mainly affects the light power density, that is, the light energy per unit area. Under the same power condition, the smaller the spot size is, the greater the optical power density is. The high power density spot is suitable for high cladding. Melting point metal powder.
4. Processing distance: also called overlap rate, refers to the distance required for the laser beam to absorb heat from the molten pool during laser cladding. In the process of laser cladding, the spot distance is an important factor affecting the cladding quality. In actual processing, when the light spot distance changes within the range of 3-5 mm, the quality of the cladding layer is good, so the light spot distance is generally controlled within 3-5 mm.
5. Overlap rate: Overlap rate refers to the overlap rate between the cladding metal powder and the substrate. Lap ratio is an important parameter that affects the surface roughness of cladding layer. The greater the overlap ratio between the cladding material and the substrate, the easier it is to obtain the cladding surface with lower roughness.
6. Cladding speed: both the linear speed and the area rate of cladding can represent the cladding speed. The actual measurement shows that when the line speed of Rio Tinto high-speed laser cladding is 20 m/min-50 m/min and the cladding thickness is 0.2-0.6 mm, the cladding efficiency is 0.6-1.2 m2/h.
7. Powder feeding mode: the powder feeder in high-speed laser cladding is the key to ensure the quality of laser cladding. The powder feeding methods of high-speed laser cladding mainly include annular powder feeding and central powder feeding. The utilization rate of central powder delivery is higher than that of circular powder delivery, but the design is difficult, and the beam needs to be surrounded by a circular ring. One week of powder feeding pipe. At present, there are many circular powder feeding applications on the market.
8. Shielding gas pressure: During high-speed laser cladding, it is easy to oxidize between the substrate and the cladding material. The oxides contained in the cladding material will cause the surface of the substrate material to become black, dark and hard, which seriously affects the surface quality of the workpiece. In order to avoid oxidation of the cladding material, it is necessary to protect the workpiece. High-speed laser cladding can be carried out under the protective gas. Generally, nitrogen or argon is used as the protective gas, mainly for powder feeding, to form a protective area around the laser cladding pool and reduce oxidation.
Source: Guosheng Laser
