Laser Drilling in Alumina Ceramics Using a Combination of Laser Pulses in the Free-Running and Q-Switched Modes

Abstract

The possibility of using a two-pulse laser action consisting of a pulse of the free-running pulse followed by the Q-switched pulse in the processes of laser drilling in alumina ceramics is considered. A diagram of a laser machine for implementing the proposed processing method and the method for determining the energy required to form the through hole and the drilling time are presented. For thermal exposure, pulsed radiation of Nd:YAG of the laser operating in the free-running mode (pulse duration 0.5 ms, energy up to 0.3 J) was used. The Q-switched pulse was generated using a second Nd:YAG laser (pulse duration 25–30 ns, energy up to 0.03 J). The laser radiation was focused on the surface of the material at one point. The time between the start of generation of the first and second lasers varied in the range of 0–1000 μs. The optimal delay time for the start of the generation of the second laser relative to the first was determined experimentally. The obtained results showed that the combination of the free-running pulse and the Q-switched pulse can significantly increase the efficiency of laser machining of ceramics and improve the hole quality. This scheme turned out to be promising for optimizing parameters of the process of laser drilling in thin-sheet alumina ceramics. The obtained results obtained have great potential in the field of precision laser machining of ceramics.

Simulation of Mechanical and Thermal Loads and Microtexturing of Ceramic Cutting Inserts in Turning a Nickel-Based Alloy

“…• the presence of microcracks due to the shrinkage of the molten material as it solidifies [22,23]; • the presence of surface morphology subjected to repeated focal overheating with the creation of near-track/weld stress zones (heat-affected zones) [24,25]; • active evaporation of the lightest materials from the processing zone [26,27]; • formation of a transitional nanoporous interlayer consisting of more refractory material components [28,29]; • increased formation of brittle structures in the near-surface layer (the formation of second-order secondary compounds on the heating surface, due to the material's active oxidation as a result of the interaction of the molten material of the cutting insert/substrate and coating with the environment) [30]; • splashing of material from the processing zone due to thermal shock [31,32].…”

Picosecond laser drilling grids in aluminium foil at 532 and 355 nm wavelengths

“…When the pulse duration is shorter than the heat diffusion time, the irradiated volume of the material is expelled before heat diffusion or thermal damage can occur. Consequently, the side effects of thermal deformation are significantly reduced as compared to longer pulses [19][20][21][22].…”