Features and efficiency of high-carbon steel ablation by a scanning beam of the nanosecond pulsed Yb:YAG laser

The experiments results on the ablation of high-carbon (> 97 % Fe, 1.3 % C) and low-carbon (> 97 % Fe, 0.3 % C) steel targets by a nanosecond pulse laser radiation scanning beam are presented. The dependence of the depth and energy efficiency of ablation on the power density in the range q = 4·108 – 1010 W/cm2 has been determined. It has been established that the maximum efficiency of material removal is achieved at q = 4·109 W/cm2 for a high-carbon steel target and in the range q = 7·108 – 5·109 W/cm2 for a low-carbon steel target. The size distribution of ejected microparticles was determined. It has been established that a back flow of particles occurs upon irradiation of high-carbon steel and the flow origin mechanism is associated with nanosized condensate particles. Based on the reflectivity measurements and the electron microscopy microstructure study of the irradiated surface, it has been suggested that the mechanism for the higher efficiency of ablation of high-carbon steel compared to low-carbon steel is the condensation process of supersaturated carbon vapors on the target surface that increases the irradiated target surface absorptivity and, consequently, the material removal efficiency of the subsequent scanning pass is increased.