Effect of laser type on hole machining of SiC/SiC composites

Abstract

SiC/SiC composites have the characteristics of high hardness and brittleness, and they are typical difficult materials to process. Laser processing is mainly used to prepare cooling holes. Millisecond and nanosecond lasers mainly use photothermal action to rapidly heat the target material, melt and gasify it, and remove the material with the help of high-speed gas flow. Due to the short pulse duration and high peak power of nanosecond laser, it is easier to realize the gasification of materials, and the thermal effect caused is less. In this paper, millisecond and nanosecond lasers are used to make holes in SiC/SiC composites respectively. The results show that for cooling holes with a diameter of 0.6 mm and an inclination angle of 25 °, the processing time of nanosecond laser is 8.7 times longer than that of millisecond laser. The two kinds of laser processed holes have certain taper, in which the hole cone angle of nanosecond laser processing is 2.12 ° and that of millisecond laser processing is 1.49 °. There are residues in the inner, outlet end and inlet end of the hole processed by millisecond laser, and there are obvious remelting oxidation zone and heat affected zone around the hole. However, there is no obvious residue inside the hole processed by nanosecond laser, there is discoloration at the inlet end of the laser, there is no discoloration at the outlet end, and there is no obvious remelting oxidation zone and heat affected zone. The results of elemental analysis show that both kinds of laser processing can cause the oxidation of materials.

Keywords

• sic/sic composites
• laser processing
• ceramic matrix composites
• nanosecond laser
• millisecond laser