High-speed laser cladding additive manufacturing technology has greatly improved the shortcomings of low processing efficiency and high processing cost of ordinary laser cladding additive manufacturing. However, people’s pursuit of improving processing efficiency and reducing processing costs is endless. How to continue to reduce processing costs is still an important part of high-speed laser cladding additive manufacturing research.

Since powder cost accounts for 80%-90% of the total cost of laser cladding additive manufacturing, improving powder utilization is an important technical problem to be solved in high-speed laser cladding additive manufacturing. To this end, it is necessary to clarify which factors are related to the powder utilization of high-speed laser cladding additive manufacturing. The following will discuss these factors one by one and discuss how to improve the powder utilization of high-speed laser cladding additive manufacturing.

1. Molten pool spot size

The primary factor affecting the powder utilization rate of high-speed laser cladding additive manufacturing is the size of the molten pool spot, that is, the size of the spot where the laser falls on the surface of the substrate. According to the laser power, the molten pool spot of high-speed laser cladding additive manufacturing can be selected between 1 mm and 5 mm. In actual work, it is necessary to select a molten pool spot of appropriate size according to the laser power of the equipment.

If the molten pool spot is too small, the powder utilization rate is low; if the molten pool spot is too large, the surface flatness of the coating will decrease. Increasing the molten pool spot can improve the powder utilization rate, but if the molten pool spot is too large, the coating flatness will decrease, so that the subsequent grinding and polishing process will also cause powder waste. Even for high-speed laser cladding additive manufacturing, the powder utilization rate cannot be considered unilaterally only in the cladding process, but the powder utilization rate after the entire cladding process and grinding and polishing should be considered.

2. The aperture of the powder outlet of the cladding head

The aperture of the powder outlet 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 powder flow diverges. In actual work, the appropriate aperture size of the powder outlet hole should be selected according to the cladding height and the size of the molten pool spot to ensure that the powder spot diameter on the substrate surface is smaller than the diameter of the molten pool spot, otherwise the powder exceeding the molten pool spot will be lost and wasted.

3. Laser power

The laser power should be large enough to ensure that the powder falling into the molten pool spot can be fully melted. When the powder feeding amount and other parameters are constant, the greater the laser power, the higher the powder utilization rate.

4. Powder feeding amount

When the laser power of the equipment is determined, the smaller the powder feeding amount, the higher the powder utilization rate, but reducing the powder feeding amount will affect the cladding efficiency. If the cladding efficiency is not considered, controlling the powder feeding amount can make the powder utilization rate reach 100%, but this approach is meaningless.

5. Cladding line speed

The line speed of high-speed laser cladding additive manufacturing is several times or even dozens of times that of ordinary laser cladding additive manufacturing. When the relative movement speed between the substrate or the cladding head is high, 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 greater the relative movement speed between the cladding head and the substrate, the lower the temperature of the molten pool, which will also reduce the powder utilization rate.

6. Workpiece volume size

For 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 more by the substrate and the molten pool temperature is not high enough. Therefore, for large-volume workpieces, to improve the powder utilization rate, a higher-power cladding equipment must be used.

7. Powder particle size

The high-speed laser cladding powder has a short action time with light, so it is necessary to select powder of appropriate particle size according to the size of the laser power. Large powder particles will cause the powder to fail to melt within a limited time, resulting in ejection and splashing losses.

The above are the seven main factors affecting the powder utilization rate of high-speed laser cladding additive manufacturing. In order to improve powder utilization and reduce the processing cost of cladding processing, it is necessary to select appropriate hardware technical parameters and cladding processing process parameters according to the specific conditions of the equipment and cladding workpiece.