Material transport during excimer-laser nitriding of iron

Abstract

The surface topology and nitrogen concentration profiles of iron irradiated with pulses of an excimer laser in a nitrogen atmosphere were studied by means of optical and scanning electron microscopy, surface profilometry, energy-dispersive x-ray spectroscopy, and resonant nuclear reaction analysis. The observations are combined to distinguish several mechanisms contributing to the material transport: ablation, redeposition of nitride from the plasma and pressure-induced lateral flow of the molten iron towards the edges of the laser spot ͑piston mechanism͒. Numerical estimates of the time and spatial evolution of temperature and pressure at the surface led to average rates of the material transport in good agreement with the experiment.

The influence of laser power and repetition rate on oxygen and nitrogen insertion into titanium using pulsed Nd:YAG laser irradiation

“…1a and b). We attribute this to the recoil pressure generated by the ejection of matter at the heart of the impact, where laser intensity is greatest [17][18][19]. It is to be noted that, for the deformation of the surface, the effect of the laser fluence is greater than that of the number of impacts.…”

“…The nitrogen dioxide in the air needs to be excited, even dissociated, before it can be inserted. That is the role of the plasma created on the surface of the target [5,17].…”

Growth of titanium oxynitride layers by short pulsed Nd:YAG laser treatment of Ti plates: Influence of the cumulated laser fluence

“…The recoil pressure is above 10 9 Pa. The molten metal is pushed back on the sides of the impact [13]. The ejection speed is around 600 m s À1 .…”

Laser nitriding of iron with laser pulses from femtosecond to nanosecond pulse duration

“…%, and greatly improved surface properties. [1][2][3] However, up to now, the nature of the laser nitriding mechanism is still not clear, because of the complicated interaction of the incident laser radiation with the molten material and the laser produced plume or plasma. A series of pulsed-laser nitriding experiments was conducted, comparing the effects of the pulse duration p ranging from nanoseconds ͓XeCl excimer laser, p ϭ55 ns, ϭ308 nm, and Nd:YAG ͑Nd doped yttrium aluminum garnet͒ laser, p ϭ8 ns, ϭ1060 nm͔ to femtoseconds ͑Ti:sapphire laser, p ϭ150 fs, ϭ750 nm͒.…”