T. Mościcki

Modelling of plasma plume induced during laser welding

A theoretical modelling of the plasma plume induced during welding of iron sheets with CO2 laser is presented. The set of equations consists of the equations of conservation of mass, energy, momentum and the diffusion equation and is solved with the use of the commercially available program Fluent 6.1. The computations are made for a laser power of 1700?W and for two shielding gases?argon and helium. The results show a significant difference between these two cases. When helium is used as the shielding gas, the plasma is much smaller and burns only where the metal vapour is slightly diluted by helium. In the case when argon is the shielding gas, there are actually two plasmas: argon plasma and metal plasma. The flowfield shows that the velocity increases in the hot region but only part of the mass flux enters the plasma core. In the case when argon is used as the shielding gas, the total absorption of the laser radiation amounts to 18?33% of the laser power depending on argon and iron vapour velocities. In the case of helium the total absorption is much lower and amounts to ~5% of the laser power.

Emission coefficients of low temperature thermal iron plasma

Iron plasma appears during material processing with laser, electric are etc., and has considerable influence on the processing conditions. In this paper emission coefficients of low temperature thermal iron plasma at atmospheric pressure are presented. Net emission coefficientsεN have been calculated for pure iron plasma as well as for Fe−Ar and Fe−He plasma mixtures. To calculate the recombination radiation the knowledge of the Biberman factorsξfbz(Te,λ) is necessary and they have been calculated from the iron photo-ionization cross sections. The calculations allow estimation of energy losses, energy radiated by plasma plume and its comparison with the energy absorbed from laser beam.

Structure and Expansion of a Plume Emitted During Laser Ablation of Multicomponent Materials

Pulsed laser deposition (PLD) is a technique frequently used for creating thin films of various materials on solid substrates. High-energy laser pulse causes evaporation of the target material, forming a plume which subsequently expands and moves with high speed from the target. Thin film of the evaporated material is deposited on the substrate placed at some distance in front of the target.