Oxygen and nitrogen are not suitable as cutting gases for titanium and titanium alloys. Because these gases, like hydrogen, are absorb into the surface, where a hard and brittle layer is form. This layer may crack, and propagation of the crack can cause component failure.
High-pressure cutting with a completely inert gas is therefore the preferred method for the laser cutting of titanium. In addition, the workpiece is often fi xed in a vessel at inert atmosphere during the cutting process. We mostly use high-purity argon and argon-helium-mixtures with a very low oxygen content (99.996%–99.999%). Helium content in the cutting gas is advantageous as high intensities in the focus cause process disturbing plasma formation. The cuts exhibit no signifi cant dross adhesion. A deep focal point position, beneath the upper surface of the sheet is advantageous.
Nickel is the base metal in a number of industrially important alloys: Inconel (Ni-Cr), Nimonic (Ni-Cr-Co), Hastelloy (Ni-Mo-Cr) and Monel (Ni-Cu).
Low-pressure oxygen-cutting – lower than 6 bar (85 psi) – we can use it to obtain high cutting speeds. But the cut edges exhibit dross and the cut surfaces are oxidised.
Although burr-free and oxide-free cuts may achieve with highpressure nitrogen, the cutting speed is reduce significantly compare with oxygen-cutting. We should put the focal point posite deep within the material, below the upper surface of the sheet.
The high refl ectivity and thermal conductivity of copper make cutting of this material quite a challenge. It must takes precautions to avoid re-refl ections of the laser beam and subsequent damage to the resonator.
Brass is one of the important copper alloys (copper-zinc alloy), and has lower refl ectivity and thermal conductivity than copper. It is therefore easier to cut with CO2 lasers. Very high laser power and a short focal length of the lens – about 63mm (2.5 in) are benefi cial.
Oxygen-cutting is preferable when cutting brass and other copper alloys with CO2 lasers. Oxygen is better suit as a cutting gas, as the oxide layer at the cut front improves absorption of the laser beam. We use both low oxygen pressures of up to 6 bar (85 psi) and high oxygen pressures of up to 20 bar (300 psi). When cutting brass at high oxygen pressures of up to 20bar (300psi), proper ventilation of the working area must provide to avoid dangerous enrichment of the atmosphere with oxygen. We can cut the maximum sheet thickness is 4–5mm (0.16–0.20 in). Sometimes, we also use high-pressure nitrogen to cut copper alloys.
Laser application is widespread in the cutting of non-metals.
We use CO2 lasers for cutting plastics, rubber, textiles, wood, ceramics and quartz. When using a 1kW CO2 laser, the maximum thickness of plastics and plywood is about 25mm (1 in).