Improving the Quality of Laser Drilling by Assisted Process Methods of Static Solution and Mist Blowing

The use of static solution-assisted laser drilling can effectively improve hole roundness, decrease taper angle, and reduce recast layer thickness and hole wall slag adhesion. However, the enormous energy of the laser will evaporate the solution to form a suspension droplet and reduce the quality and efficiency of laser drilling. To deal with this defect, the mist-blowing method was used to reduce the influence of droplets on the taper angle and recast layer. In this work, the effect of wind speed on drilling quality was examined, and laser drilling in air, water, and NaCl solution was carried out to analyse the effect of solution composition on hole wall morphology. The results showed that a speed fan with a proper wind speed that disperses the droplets formed in the processing area can significantly reduce the refraction and scattering of the laser, and the taper angle and roundness of the drilling hole were also reduced by 15.6% and improved by 2.4%, respectively, under the wind speed of 2 m/s. The hole wall morphology showed a thicker recast layer and cracking in air, while it was thinner in water and there was little or no layer in the NaCl solution in the same current. When drilling in NaCl, the taper angle and roundness of the drilling hole were reduced by 4.13% and improved by 2.11%, respectively, compared to water. Due to the mechanical effect of the laser in the NaCl solution, the impact force on the material was much greater than that in water. The solution cavitation effect, generated by the absorption of laser energy, caused an explosive impact on the molten material adhered to the surface of the hole wall. Above all, drilling in the NaCl solution with a current of 200 A and a wind speed of 2 m/s was the optimal condition for obtaining the best processing quality.