Effect of defocusing distance along Z axis on laser cladding forming

The variation of distance between laser head and substrate (named defocus distance) has a considerable effect on powder utilization efficiency and energy density, therefore affecting the laser cladding forming (LCF) process. Orthogonal experiments L16 (44) of the four parameters: laser power, scanning speed, gas flow rate and defocusing distance and single factor experiment of the defocusing distance along Z axis were conducted to investigate the coupling effects of these parameters on LCF process. The result of orthogonal experiment suggests that all four parameters play important roles in LCF, and the order of factors which affect the cladding efficiency is: laser power>gas flow rate>defocusing distance>scanning speed. The result of the single factor experiment indicates that the optimal cladding quality occurs when the defocusing distance reaches a certain level. The maximum cladding layer height can be achieved when the defocusing distance is 5mm. The cladding layer height is reduced when the defocusing distance is less or larger than 5mm. It is proved that the powder utilization efficiency gradually increases and then decreases when the defocusing distance keeps increasing.