CC BY
14LM-O-4
Laser micro-processing of graphite with pulsed ytterbium laser
T. Doualle1*, M. Reymond12, Y. Pontillon1, L. Gallais2
1 - CEA, DES, IRESNE, DEC, Cadarache F-13108 Saint-Paul-Lez-Durance, France
2 - Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
*email adress : thomas.doualle@cea.fr
Lasers are essential tools for macro and micro-processing for a whole range of materials in scientific research and industry. Processes involving lasers provide a unique solution with minimum mechanical and thermal influence on the processed part due to their selective energy control and deposition and allow generally high processing speeds.
In this work, we study laser micro-processing of graphite. This material is used in large number of scientific and industrial applications because of some of its peculiar properties: it is extremely resistant to heat, nearly inert in contact with almost any other material, has good thermal and electrical conductivity. Its refractory properties in combination with its mechanical properties make it a material of choice in very demanding applications in the nuclear or aerospace fields and lasers can be used in various ways to process it. The laser micro-processing of graphite employing an Ytterbium fibre laser delivering microsecond pulses at 1080 nm has been experimentally investigated, with the support of a numerical model to investigate and understand the laser ablation mechanisms processes.
High aspect ratio craters were obtained, with 400 ^m depth and 50 ^m diameter, and excellent cr ater quality with negligible heat affected zone (HAZ). We have applied micro-second laser pulse ablation approach for cutting graphite samples by identifying the best combination of scanning speed and repetition rate (beam overlap) to optimize the cut. We have shown that such laser cutting technique can produce parts with excellent quality (reduced affected area, no recast layer, no micro-cracks and no debris from ejected material) with high efficiency as shown in the Figure 1.
To go further in the investigation and understand the laser ablation mechanisms, simulations are conducted with the commercial software COMSOL which is based on the Finite Element Method. Heat transfer by conduction associated with deformed geometry and ray-tracing modules are employed for the analysis of the thermal effects, material evaporation and laser propagation on the fabricated structures.
1,5 mm Pj □
100 nm
Figure 1 - SEM measurements of a pattern. (a) and (b) are top-views and (c) is the corresponding cross-section view of the part observed in
(b).
