Influence of assist gas in fibre laser cutting of aluminum-copper alloy

Abstract

Fibre laser cutting is an emerging field in laser materials processing. This new generation of high power solid state lasers offers a lot of advantages as compared to traditional CO2 lasers in the laser cutting field. The combination of high output power, reduced focal spot and low divergence of the laser beam in these sources is extremely interesting for cutting applications. Several works have shown that fibre laser cutting enables processing with higher production rates than the processing assisted by means of CO2 laser, reaching similar levels of quality when thin sheets are cut. However the quality of the cuts is substantially worsened with the increase in thickness due to the difficulty in the extraction of the molten material by the assist gas jet because of the complicated penetration of the gas jet in narrow kerfs. Moreover, the high brightness of these sources modifies the physical mechanisms which take part in the process and an elevated recoil pressure makes cut quality worse.In this work, an attempt to improve cut quality results in the fibre laser cutting process was accomplished. An off-axis supersonic nozzle in conjunction with a fibre laser was utilized in order to process a Cu-Al alloy. Parameters related to assist gas delivery system were studied. A microstructural characterization, grain morphology, kerfs’ dimensions and surface finish of the performed cuts were carried out.Fibre laser cutting is an emerging field in laser materials processing. This new generation of high power solid state lasers offers a lot of advantages as compared to traditional CO2 lasers in the laser cutting field. The combination of high output power, reduced focal spot and low divergence of the laser beam in these sources is extremely interesting for cutting applications. Several works have shown that fibre laser cutting enables processing with higher production rates than the processing assisted by means of CO2 laser, reaching similar levels of quality when thin sheets are cut. However the quality of the cuts is substantially worsened with the increase in thickness due to the difficulty in the extraction of the molten material by the assist gas jet because of the complicated penetration of the gas jet in narrow kerfs. Moreover, the high brightness of these sources modifies the physical mechanisms which take part in the process and an elevated recoil pressure makes cut quality worse.In this work, an ...