Spatter reduction during titanium microdrilling using pulsed fiber laser

Abstract

The request of small features obtained by means of laser technology has been growing in several fields, such as micromechanical, microelectronic and biomedical sectors. Commercially pure (c.p.) titanium and its alloys are very promising materials in biomedical and aerospace applications, such as prostheses and engine turbine blades. However high tendency of c.p. titanium to produce spatter and remelted material makes diffusion of microfeatures machined by laser sources quite difficult. Ultra-short-pulse lasers in the range of femtoseconds or picosenconds can be used to eliminate the spatter production, since they work in non-thermal ablation mode. However, these laser sources are very expensive and their material removal rates are very limited, if compared with the material removal rate of pulsed lasers in nanosecond regime.In this work the study of laser percussion drilling of c.p. titanium making use of an innovative laser source, such as a nanosecond pulsed fiber laser, was proposed. In this case high repetition rate, short pulse width and good pulse energy of fiber laser should ensure high removal rates, while the high quality of the pulsed fiber laser, which can be finely focused, should minimise the spatter production.In the paper the main characteristics of the fiber laser source were presented: pulse width and shape as well as pulse energy as function of the main process parameters, i.e. repetition rate and pump current. The drilling time was also measured making use of two fast photodiodes. Then the influence of these process parameters on the spatter volume was studied using a factorial design. Finally, a method to reduce spatter on the entrance hole was developed and investigated.The request of small features obtained by means of laser technology has been growing in several fields, such as micromechanical, microelectronic and biomedical sectors. Commercially pure (c.p.) titanium and its alloys are very promising materials in biomedical and aerospace applications, such as prostheses and engine turbine blades. However high tendency of c.p. titanium to produce spatter and remelted material makes diffusion of microfeatures machined by laser sources quite difficult. Ultra-short-pulse lasers in the range of femtoseconds or picosenconds can be used to eliminate the spatter production, since they work in non-thermal ablation mode. However, these laser sources are very expensive and their material removal rates are very limited, if compared with the material removal rate of pulsed lasers in nanosecond regime.In this work the study of laser percussion drilling of c.p. titanium making use of an innovative laser source, such as a nanosecond pulsed fiber laser, was proposed. In this case high ...