Key parameters of high-speed laser cladding process and their influence on cladding effect

1. Laser power
Power directly affects the amount of melted powder and coating efficiency per unit time. When other working parameters are determined, low power may result in incomplete powder melting, pitting after polishing, insufficient bonding force, and low coating hardness; If the power is too high, it may be due to excessive melting of the melt groove, resulting in diagonal wrinkles on the surface.

2. Powder feed quantity
When powder encounters laser, it absorbs laser energy. The larger the amount of powder, the more laser energy is absorbed. If the amount of powder is too large, the laser energy will be insufficient, the coating will not melt through, and there will be pitting after polishing. The substrate will not melt off, and the coating and substrate cannot achieve metallurgical bonding, resulting in coating peeling. Large amount of powder, low utilization rate of powder; Low powder usage and high powder utilization rate.

3. Linear velocity
The higher the linear velocity, the thinner the cladding, and the lower the linear velocity, the thicker the cladding. If the line speed is too high, the substrate will not form a molten pool, the coating will not have metallurgical bonding with the substrate, the cooling of the melt groove will be slow, the red tail will be too long, and peeling will occur. Linear speed can improve coating hardness and powder utilization.

4. Step by step
The smaller the step, the higher the grinding ratio, and the finer the coating surface. The larger the step, the smaller the overlap rate, and the more obvious the coating stripes. The step will affect the dilution rate. When the step size is small, the laser energy irradiated on the substrate is small and the dilution rate is low. When the step is large, the laser energy irradiated on the substrate is high and the dilution rate is high.

5. Air delivery rate
Gas has two functions: one is to transport powder, and the other is to protect high-temperature coatings and prevent oxidation. The amount of powder delivered is too small, which can easily cause powder blockage; The powder feeding air volume is too large, the powder feeding speed is too fast, the spraying volume is large, and the powder utilization rate is low. Generally speaking, argon gas has better protection and higher coating quality than nitrogen gas.

6. The height of the nozzle
The nozzle is too high, causing large powder dispersion and low powder utilization rate; If it is too low, the nozzle is prone to sticking powder during melting.