Laser drilling with gated high power fiber lasers

Abstract

To determine if drilling holes in aerospace engine materials with a high power fiber laser was feasible, a 10 kW continuous wave fiber laser with a uniform power distribution beam profile was operated with pulse widths of 50 and 100 µsec, gated at frequencies from 10 Hz to 18 kHz. The holes were cross sectioned and examined for heat affected zone, recast and remelt. These thicknesses were combined to define the Heat Affected Layer (HAL) which was graphed Vs frequency to determine the effects of high frequency pulsed drilling on metallurgy. This method was repeated for two cases: with coaxial assist gas and without any assist gas. Additionally, hole depth (per pulse) Vs frequency was plotted to determine any changes in drilling efficiency for all combinations of pulse width, air assist and no air assist. The results show that the laser can be operated in a pulsed mode and will drill acceptable holes in aerospace engine materials. They also show that there may be some advantages to operating the laser in a high frequency pulsed mode with respect to drilling speed, hole uniformity and the reduction of HAL. This method could lead to decreased processing costs, faster production speeds, better process control and part uniformity, with no detriment to part quality.To determine if drilling holes in aerospace engine materials with a high power fiber laser was feasible, a 10 kW continuous wave fiber laser with a uniform power distribution beam profile was operated with pulse widths of 50 and 100 µsec, gated at frequencies from 10 Hz to 18 kHz. The holes were cross sectioned and examined for heat affected zone, recast and remelt. These thicknesses were combined to define the Heat Affected Layer (HAL) which was graphed Vs frequency to determine the effects of high frequency pulsed drilling on metallurgy. This method was repeated for two cases: with coaxial assist gas and without any assist gas. Additionally, hole depth (per pulse) Vs frequency was plotted to determine any changes in drilling efficiency for all combinations of pulse width, air assist and no air assist. The results show that the laser can be operated in a pulsed mode and will drill acceptable holes in aerospace engine materials. They also show that there may be some advantages to operating the laser in a ...