What factors are related to the utilization rate of high-speed laser cladding powder?
High speed laser cladding technology has greatly improved. The pursuit of improving the processing efficiency and reducing the processing cost is endless. How to continue to reduce the processing cost is still an important content of high-speed laser cladding research.
Since the cost of powder accounts for 80% - 90% of the total cost of laser cladding, improving the utilization rate of powder is an important technical problem to be solved in high-speed laser cladding. Therefore, we must find out what factors are related to the powder utilization rate of high-speed laser cladding. We will discuss these factors one by one and discuss how to improve the powder utilization rate of high-speed laser cladding.
(1) spot size of molten pool
The primary factor affecting the utilization rate of high-speed laser cladding powder is the spot size of the molten pool, that is, the spot size of the laser falling on the surface of the substrate. According to the laser power, the spot of the high-speed laser cladding pool can be selected between 1 mm and 5 mm. In actual work, it is necessary to select a proper size of weld pool spot according to the laser power of the equipment.
The spot of molten pool is too small and the powder utilization rate is low; The spot of the molten pool is too large, and the flatness of the coating surface decreases. Increasing the spot of the molten pool can improve the utilization rate of powder, but if the spot of the molten pool is too large, the flatness of the coating will be reduced, so the subsequent grinding and polishing process will also cause waste of powder. Even for high-speed laser cladding, the utilization rate of powder can not be considered only in the cladding process, but the comprehensive utilization rate of powder after grinding and polishing in the whole cladding process.
(2) diameter of powder outlet hole of cladding head
The diameter of the powder outlet hole of the cladding head determines the thickness of the powder flow. The smaller the aperture, the finer the powder flow, but the finer the powder flow, the faster the dispersion of the powder flow. In the actual work, the appropriate diameter of the powder outlet hole should be selected according to the cladding height and the spot size of the molten pool, so as to ensure that the powder spot diameter on the surface of the substrate is smaller than the spot diameter of the molten pool, otherwise the powder beyond the spot size of the molten pool will be lost and wasted.
(3) laser power
The laser power should be large enough to ensure that the powder falling into the spot of the molten pool can be fully melted. When the powder feeding amount and other parameters are constant, the higher the laser power, the higher the powder utilization rate.
(4) size of powder feeding
When the laser power of the equipment is determined, the smaller the powder feeding amount, the higher the powder utilization rate. However, reducing the powder feeding amount will affect the cladding efficiency. If the cladding efficiency is not considered, the powder utilization rate can reach 100% by controlling the powder feeding amount, but this practice is meaningless.
(5) cladding linear spee
The linear velocity of high-speed laser cladding is several times or even tens of times of that of ordinary laser cladding. When the relative movement speed between the substrate or the cladding head is large, the kinetic energy of the powder particles on the substrate surface is large, so the powder ejection is large and the powder utilization rate will be reduced. In addition, when the laser power is determined, the higher the relative movement speed between the cladding head and the substrate, the lower the temperature of the molten pool, and the lower the powder utilization rate.
(6) workpiece volume
With the same cladding parameters, the larger the diameter (volume) of the workpiece, the lower the powder utilization rate. This is because when the volume is large, the laser energy is absorbed by the matrix more, and the temperature of the molten pool is not high enough. Therefore, for large volume workpieces, it is necessary to use higher power cladding equipment to improve the powder utilization rate.
(7) powder particle size
The high-speed laser cladding powder has a short interaction time with light, so it is necessary to select the powder with appropriate particle size according to the size of laser power. The large powder particles will cause the powder to not melt in a limited time, resulting in ejection splash loss.
The above are seven main factors affecting the utilization rate of high-speed laser cladding powder. In order to improve the utilization rate of powder and reduce the processing cost of cladding processing, it is necessary to select appropriate hardware technical parameters and cladding processing parameters according to the specific conditions of equipment and cladding workpiece.
Here again, it is emphasized that the powder utilization rate should consider the powder utilization rate of the whole processing process, rather than the powder utilization rate of the simple cladding process. The powder utilization rate of ordinary laser cladding can reach 100%, but the comprehensive powder utilization rate is often less than 50%.
Post time: Aug-24-2022