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  • 1
    ISSN: 1432-0630
    Keywords: 61.80.Ba ; 52.75.-d ; 81.60.Bn ; 76.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Armco iron samples were surface nitrided by irradiating them with pulses of an excimer laser in a nitrogen atmosphere. The resulting nitrogen depth profiles measured by Resonant Nuclear Reaction Analysis (RNRA) and the phase formation determined by Conversion Electron Mössbauer Spectroscopy (CEMS) were investigated as functions of energy density and the number of pulses. The nitrogen content of the samples was found to be independent of the number of pulses in a layer of 50 nm from the surface and to increase in depths exceeding 150 nm. The phase composition did not change with the number of pulses. The nitrogen content can be related to an enhanced nitrogen solubility based on high temperatures and high pressures due to the laser-induced plasma above the sample. With increasing pulse energy density, the phase composition changes towards phases with higher nitrogen contents. Nitrogen diffusion seems to be the limiting factor for the nitriding process.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0630
    Keywords: 61.80.Ba ; 52.75.-d ; 81.60.Bn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Laser nitriding of Armco iron in nitrogen was studied for KrF-excimer-laser irradiation. The influence of the energy density and number of pulses on the nitrogen take-up and the nitride phases formed was investigated using Resonant Nuclear Reaction Analysis (RNRA) and Mössbauer spectroscopy. Besides the original a-iron, austeniteγ-Fe(N), martensiteα′-Fe(N),ε-Fe2+χN, andα″-Fe16N2 were identified. The fraction of the e-phase was found to increase with the number of pulses and the energy density. A threshold energy density of 1.8(2) J/cm2 for the laser nitriding process was found.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 69 (1999), S. S795 
    ISSN: 1432-0630
    Keywords: PACS: 81.65.Lp; 61.80.Ba; 62.50.tp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Laser nitriding of iron and other metals is governed by the complicated interplay of the laser–plasma–liquid surface interactions which lead to a superposition of several mechanisms. This article reports on the influence of the nitrogen gas pressure on the nitriding process for stainless steel. The effects of the nitrogen gas pressure on the nitrogen depth profiles and the phase formation are revealed by resonant nuclear reaction analysis, Mössbauer spectroscopy, and X-ray diffraction. We found that the surface nitrogen concentration reaches 10 at. % with a mean value of about 7.5 at. % in the first 150 nm. There seems to be a pressure window between 0.1 and 0.7 MPa for the most efficient treatment. In the surface layer, an additional γ-Fe(N) phase can be distinguished from the original γ-phase of the stainless steel.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4619-4624 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser nitriding is a very efficient method to improve the mechanical properties, surface hardness, corrosion, and wear resistance of iron and steel, with the advantages of a high nitrogen concentration, fast treatment, and accurate position control, and without any undesired heating effect on the substrate. However, the stability of laser-produced iron nitrides is still under investigation. This article reports investigations of the thermal stability of these iron nitrides upon annealing treatments, which were conducted both in vacuum and air. The phase and elemental composition of the nitride layers were deduced from conversion electron Mössbauer spectroscopy, resonant nuclear reaction analysis, and grazing incidence x-ray diffraction. The surface hardness was measured by the nanoindentation method. In laser-nitrided iron, two critical temperatures are found: at 523 K the predominant iron-nitride phase changes from the γ/ε to the γ′ phase. When the temperature exceeds 773 K, all of the nitrogen has escaped from the surface layer. For annealing in air the nitrogen escapes completely already at 673 K, where a thick oxide layer has formed. Stainless steel proved to be more stable than iron, and even up to 973 K no new phases or oxides were produced, here, also, only at 973 K the nitrogen content decreased significantly. Therefore, laser-nitrided stainless steel is well suited for applications. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1349-1351 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Solid phase epitaxial growth of ion beam-amorphized α-quartz has been studied by means of Rutherford backscattering spectrometry in channeling geometry. α-quartz single crystals were irradiated with Cs+ and Xe+ ions and annealed in air or in vacuum at 500–900 °C. Complete epitaxial regrowth has been observed in the Cs-irradiated samples, after 875 °C annealing in air. On the other hand, vacuum annealing provided only incomplete regrowth of the amorphous layer, while Xe-irradiated α-quartz could not be regrown up to 900 °C. The behavior of Cs in the recrystallization process is discussed in terms of the SiO2-network topology. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 168-178 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser nitriding of iron and other metals is governed by the complicated interplay of the laser–plasma–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 ε nitride is only found for raw-beam irradiation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3611-3618 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, our results on the epitaxial crystallization of ion-bombarded crystalline silicon dioxide (α quartz) are reviewed. The epitaxial recrystallization of amorphized layers was achieved after alkali irradiation and annealing in air in the temperature range 650–875 °C. The systematic behavior of alkali ions in enhancing the regrowth rate both with decreasing ion size and increasing concentration is shown. The role of oxygen in the recrystallization was investigated by means of nuclear reaction analysis, by performing thermal treatments of the samples in 18O. A large amount of 18O diffuses inside the amorphous layer in the alkali-ion implanted samples at 600–800 °C. From the strong correlation between the migration of 18O and implanted alkali, it was possible to gain further insights into the recrystallization mechanism. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1922-1922 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 153-155 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In spite of its technological importance, the basic mechanisms of laser nitriding of metals and alloys are hardly understood. The nitrogen depth profiles achieved by laser nitriding of pure iron were measured with high accuracy by resonant nuclear reaction analysis and described by two superimposed diffusion profiles. Using simple estimates, together with the results of marker experiments and laser treatments in 15N-isotopically enriched atmospheres, the development of these profiles with the number of pulses can be simulated in excellent agreement with the experimental results. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 1091-1093 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pulsed-laser nitriding is an attractive method to improve metal surface properties, such as hardness, wear, and corrosion resistance, with the advantage of simple experimental setup, rapid treatment, and precise process control. Here, the dependence of the laser nitriding process on the laser pulse duration was investigated over five orders of magnitude in a series of experiments employing pulsed lasers ranging from nanosecond excimer laser pulses (55 ns) and Nd-doped yttrium aluminum garnet (Nd:YAG) laser pulses (8 ns), to ultrashort Ti:sapphire laser pulses (150 fs). The results revealed that for all laser pulse durations and different wavelengths a large nitriding effect was observed. The excimer laser shows the highest nitriding efficiency. The basic processes for the femtosecond pulsed laser are not well understood but seem to result at least partly from processes within the plasma, whereas nanosecond nitriding is based mainly on processes within the liquid/solid surface. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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