Central powder-feeding laser cladding technology is a new powder-feeding technology developed on the basis of paraxial powder-feeding technology and coaxial powder-feeding technology. The technology is mainly used in high-speed laser cladding technology so that high-speed laser cladding technology can play its technical advantages to the maximum extent (smooth surface, high efficiency, high powder utilization rate).
Central powder feeding technology is referred to as optical coating technology, that is, a single beam powder channel is arranged in the center of the cladding head, and the laser beam is distributed around the metal powder in a ring or multi-beam circumferential distribution. Metal powder in practical work, from the center channel under the action of gravity and pneumatic output, peripheral laser and metal powder above the substrate meet in one place, in the center position of metal powder surrounded by a laser beam to fully absorb the light energy into molten or partially molten state, after the molten state of the surface of the metal powder into the matrix of the molten pool, in the density of substrate surface leveling metallurgical cladding layer.
Schematic diagram of coaxial powder feeding laser cladding.
The following is the center of the powder laser cladding technology and several other powder feeding methods are different, Guo Sheng Laser will do focus on the introduction of technology:
1. The utilization rate of metal powder can reach 90%
Compared with coaxial pneumatic powder feeding, the characteristic of central powder feeding is that the powder is a single powder flow, and there is no impact and scattering of powder flow in different directions. In addition, in the vertical downward cladding processing, you can use a lower powder pressure, so that one side of the flour flow speed is relatively slow, powder and laser action time is long, more easy to powder in the melting pool above the melting. On the other hand, the lower velocity of the powder flow also reduces the ejection between the powder flow and the matrix. The practical application shows that the splashing is reduced obviously and the powder utilization is increased greatly.
2. High stability of optical path, can be a long-time generation of beam
In comparison, the laser beam of coaxial powder feeding laser cladding technology and axial powder feeding laser cladding technology directly irradiates the molten pool, the surface of the molten pool is very smooth, with high laser reflectance, so the optical path system of the two-laser cladding technology is greatly affected by the thermal radiation of the laser molten pool, and the long-term light stability is poor. The central powder feeding design of the general laser beam along the periphery has a certain Angle of the output to the molten pool, the light outlet dispersed multiple light port is small, and has a certain Angle with the molten pool, avoid the laser action zone direct thermal radiation, the optical system is safer. The same center powder feeding metal powder splash is small, moreover, the optical path has a certain tilt angle, the impact of splash is very small.
3. High Efficiency of Cladding
Center powder feeding technology powder utilization rate is high, laser energy utilization is sufficient, can achieve very high cladding efficiency (unilateral 0.5-0.7mm thickness, cladding efficiency up to 0.7-1.2㎡/h). Low dilution rate of cladding layer. Due to the high speed of cladding line, the existence time of molten pool is very short, so the dilution rate of the cladding layer is very low in ultra-high-speed laser cladding technology. Ultra-high speed laser cladding technology also has the characteristics of good roughness of cladding layer, good crack resistance and small deformation of workpiece. Ultra-high speed laser cladding technology produces thin cladding layer, which is very suitable for the preparation of pre-protective coating on the surface of new parts.
4. The advantages of central powder feeding over coaxial pneumatic powder feeding
Compared with coaxial pneumatic powder feeding, the characteristic of central powder feeding is that the powder is a single powder flow, and there is no impact and scattering of powder flow in different directions. In addition, in the vertical downward cladding processing, you can use a lower powder pressure, so that one side of the flour flow speed is relatively slow, powder and laser action time is long, more easy to powder in the melting pool above the melting. On the other hand, the lower velocity of the powder flow also reduces the ejection between the powder flow and the matrix. The practical application shows THAT the spatter is obviously reduced, the spark is quite gentle, and the powder utilization is greatly improved.
Coaxial pneumatic powder feeding
To summarize the above analysis, paraxial powder-feeding and coaxial powder-feeding have been developed for a long time and have not been widely applied due to their respective technical characteristics and limitations. Central powder feeding technology can compensate for the technical defects of both, with a number of technical advantages. With the perfect combination of high-speed laser cladding and central powder feeding technology, high efficiency and high-quality laser cladding effect will conquer more fields of the market. With the application and promotion of more enterprises, in the near future, high-speed laser cladding + central powder feeding technology will become the mainstream application of laser cladding and this technology will also occupy a larger market share in the field of the metal surface.