Influence of the spatial laser intensity distribution on laser nitriding of iron

Abstract

Laser nitriding of iron and other metals is governed by the complicated interplay of the laserplasma-solid interactions which lead to a superposition of several mechanisms. This work reports on the drastic influence of the spatial laser intensity distribution on the nitriding process. The effects of the lateral laser intensity on the nitrogen lateral and depth profiles, the phase formation, the surface topology, and the microhardness are revealed by resonant nuclear reaction analysis, Mössbauer spectroscopy, surface profilometry, and nanoindentation. Homogeneous laser beams lead to a strong reduction or almost the absence of the piston mechanism, thus confining the nitriding and the transport processes to the laser spot and avoiding the fallout. The details are discussed in relation to the results obtained for the raw-beam irradiations. Much higher nitrogen saturation concentrations can be achieved with a homogenized beam, but the surface hardness and the hardening depth are lower than in the case of irradiation with the raw beam. The ⑀ nitride is only found for raw-beam irradiation.

CFD Simulation of Aerosol Deposition in an Anatomically Based Human Large–Medium Airway Model

“…The simulated extrathoracic (oral) deposition efficiency was compared with the best-fit relation obtained by Cheng et al 11 and with the best-fit relation by Grgic et al 19 The computed left vs. right lung deposition based on the large-medium airway model was compared with the values based on in vivo experiments on human subjects by Bennett et al 5,6 The computed average deposition efficiency in each generation was compared with experimental measurements on airway casts by Schlesinger et al 47 and Gurman et al 20 Cheng et al 11 obtained a best-fit relation for oral airway deposition efficiency based on previous in vivo measurements on human subjects:…”

“…In the study of Bennett et al 5,6 healthy subjects inhaled radiolabeled monodisperse aerosol ( 99m Tc-iron oxide, 3.5 lm mass median aerodynamic diameter) boluses (40 mL) to a volumetric front depth of 70 mL into the lung at lung volumes of 50, 70, and 85% of total lung capacity (TLC) end inhalation. By gamma camera analysis regional deposition was obtained, especially the ratio between the left and right lungs.…”

“…7). The ratio of left vs. right lung deposition was compared to the in vivo experiments on human subjects by Bennett et al, 5,6 where subjects inhaled 3.5 lm aerosol particles at 15 L/min to shallow lung depths. In Fig.…”

Nitriding of Interstitial Free Steel in Potassium–Nitrate Salt Bath

“…2,3) To improve the surface hardness, wear and corrosion resistance, fatigue life, as well as global mechanical performance of pure iron and simple iron alloys, nitriding has been widely used in industries. Many nitriding processes have been applied to pure iron and low carbon steels, for instance, gas nitriding, [4][5][6][7][8][9][10] salt bath nitriding, 11) plasma nitriding, 10,[12][13][14][15][16] plasma immersion ion implantation (PIII), [16][17][18][19][20] laser nitriding, [21][22][23][24][25] and ion implantation nitriding. 26) Although the above methods are well established, some of them such as modern nitriding techniques still have some disadvantages from an engineering viewpoint because they require the use of rather complicated and expensive apparatus, and cannot, in general, produce thick nitrided layers.…”

Carburation d'alliage d'aluminium par traitement de surface par laser excimère

“…Pour durcir la surface d'un alliage il a été montré que le traitement par laser en atmosphère d'azote permet la formation de nitrures sur plusieurs microns sur de l'acier [1,2], et sur de l'aluminium [3][4][5]. Le même traitement sur l'alliage AlSi 7% Mg 03% en atmosphère de gaz carboné (C^HJ doit permettre l'incorporation de carbone et la formation de carbures.…”