Study on picosecond pulse laser ablation of Cr12MoV cold work mold steel

Highlights: • Ablation of Cr12MoV is investigated by using a picosecond laser at 1064 nm, 532 nm and 355 nm. • A highest ablation rate of 50 nm/pulse for 532 nm is obtained at low laser fluence. • A steep jump of ablation rate is observed for 532 nm at higher laser fluence. • Different plasma absorption mechanisms dominate at different wavelengths. Cr12MoV has wide applications in the molds and dies industry. However, it is also a hard-to-machining material due to its high mechanical strength and hardness. Area ablation of Cr12MoV cold-work mold steel was carried out using a picosecond (ps) pulse Nd:YVO₄ laser. The effects of laser fluence and wavelength on the ablation rate and machining quality were investigated with wavelengths of 1064 nm, 532 nm and 355 nm. The experimental results indicate a logarithmic increase of the ablation rate to a maximum value of ~ 41 nm/pulse with the increase of laser fluence using the wavelengths of 1064 nm and 355 nm. For the wavelength of 532 nm, an ablation rate of ~ 33 nm/pulse is achieved at low laser fluence of 8.28 J/cm², then increases logarithmically into about 54 nm/pulse at 25.10 J/cm², and then decreases steeply into almost zero as the laser fluence increases above 25.10 J/cm². For the three laser wavelengths, different pore sizes were observed in the laser ablation region. The surface roughness increases exponentially with the increase of the laser fluence. The influence mechanisms of laser fluence and wavelength on the laser ablation rate and machining quality were systematically analyzed and discussed in this paper.