Einfluß von Sauerstoffzusätzen beim Gasnitrieren auf den strukturellen Aufbau von Nitrierschichten

Spies, H.‐J.; Schaaf, Peter; Vogt, Felix

doi:10.1002/mawe.19980291008

Cited by 13 publications

(4 citation statements)

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“…The measured XRD reflections f peak (x) are a sum of physical and instrumental influences, which can be treated as a convolution given in (3). Line broadening in XRD arises mainly due to three factors: the machine influence, the strain broadening and the effects based on finite grains (size effect).…”

Section: Xrd Peak Analysismentioning

confidence: 99%

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Microstructure of TiN coatings synthesized by direct pulsed Nd:YAG laser nitriding of titanium: Development of grain size, microstrain, and grain orientation

et al. 2008

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Pure titanium was irradiated by pulsed Nd:YAG laser irradiation in nitrogen atmosphere. As a result, nitrogen uptake and diffusion occurred and a TiN layer was synthesized at the titanium surface. These TiN coatings were analyzed by X-ray diffraction and the diffraction patterns were investigated in detail, in order to obtain more information about the physical processes during the coating formation. The diffraction peaks were fitted by Pearson VII profiles and the grain size and the microstrain were determined by the analysis of line broadening and peak shifts, using the Williamson-Hall and the Warren-Averbach formalisms. Additional single-line analyses were performed by means of the method of Langford and Keijser to obtain information about the preferred grain orientation and the texture development. The maximum grain size was about 100 nm and a corresponding average lattice strain of 0.002 was found. A relation between the treatment parameters and the coating properties, such as grain size and microstrain, can be shown. Thus, it was possible to determine optimal scan parameters for material processing and to establish the physical limits of the coating properties.PACS 81.65.Lp; 81.15.Fg; 61.10.Nz; 68.55.Jk IntroductionNitriding and carburizing of metals are well known techniques to improve the tribological properties like hardness and wear resistance of technical surfaces [1]. As an example, plasma-and gas nitriding are established methods for surface treatment [2,3]. Alternatively, it is possible to treat the surface with laser radiation and to directly synthesize hard coatings [4][5][6][7][8]. Previous works have shown the successful synthesis of titanium nitride with laser irradiation [9][10][11]. Here, a Q-switched Nd:YAG laser was used for the nitriding treatment. The main advantages of this method are a reduction of the processing time and the negligible heat load for the workpiece. Stress, microstrain and inhomogeneity remain the main problems. Also the texture of cubic titanium nitride is a decisive factor for the technical quality of the coatings, as the u Fax: +49-551-39-4493, E-mail: pschaaf@uni-goettingen.de texture influences strain development and finally crack formation and propagation. Some investigations on texture and strain development in relation to the process parameters have been reported in the literature [12][13][14].This work resolves the resulting grain size and strain development and relates them to laser treatment parameters like scan parameters. In this way, one can try to predict optimum treatment parameters for optimum coating properties, i.e. find parameters that minimize the lattice strain in order to reduce crack formation and propagation. Experiments 2.1 Sample treatmentConventional α-titanium (purity > 99.98%) was used for the treatments. Titanium sheets of 1 mm thickness were cut into pieces of 15 × 15 mm 2 and used in the asreceived state without any further treatment.For laser nitriding, the samples were placed in a chamber which was first evacuated and then fil...

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Section: Xrd Peak Analysismentioning

confidence: 99%

“…As an example, plasma-and gas nitriding are established methods for surface treatment [2,3]. Alternatively, it is possible to treat the surface with laser radiation and to directly synthesize hard coatings [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Microstructure of TiN coatings synthesized by direct pulsed Nd:YAG laser nitriding of titanium: Development of grain size, microstrain, and grain orientation

et al. 2008

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“…The processes and the structure of the corrosion layers caused by nitridation can be derived from kinetic considerations and it is known from the experience with nitriding [13,14] and oxinitriding [15,16], Fig. 13 shows the layers formed by ingress of nitrogen, upon oxidation growth of the oxides Fe 3 O 4 and FeCr 2 O 4 should occur by outward diffusion of cations.…”

Section: Kineticsmentioning

confidence: 99%

“…The NH 3 -H 2 O is also oxidizing, and according to the experience from "gas oxinitriding" an oxide layer grows on the iron nitrides, which is porous so that nitrogen can penetrate [15,16]. It is reported that the nitridation rate is even enhanced in the presence of oxidizing gases H 2 O, CO 2 or air.…”

Section: Kineticsmentioning

confidence: 99%

Nitridation in NH₃‐H₂O‐mixtures

Grabke

Strauß

Vogel

2003

Materials & Corrosion

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Exposures were conducted of iron, nickel, ferritic 1‐18%Cr steels, austenitic 18%Cr‐9%Ni‐ and 20%Cr‐31%Ni‐steels and a 16%Cr‐Ni‐base alloy at 500°C in He‐30%H2O and 70%H2O‐30%NH3, to compare the corrosion behaviour of these materials in water vapor as in conventional power plants with their behaviour in a NH3‐H2O mixture, i.e. under conditions of the “Kalina‐cycle”. After 50 h in He‐H2O generally a dense oxide scale had grown on iron and on the steels, whereas the scale grown in NH3‐H2O was porous, due to initial formation of the γ′‐ and ε‐nitrides, which are converted to Fe3O4 later. The porous scale allows internal nitridation of the Cr‐steels, nitrogen is transferred into the metal phase and reacts to finely dispersed CrN‐precipitates. This process causes stresses in the material and formation of cracks. The higher the Cr‐content of the material, the worse is the damage of the materials surface.Least corrosion damage occurs for iron and the 1%CrMo‐steel, however, the inward penetration of nitridation is greatest, and after 5 years on the low Cr‐steel a layer of about 15 mm would be embrittled by internal nitridation, formation of γ′ and ε‐nitride layers and external oxidation.Nickel is strongly damaged by intermediate formation of instable Ni3N, which causes internal stresses and cracking, but also pore formation by its decomposition. The surface region of the 15%Cr‐Ni‐base alloy is also destroyed by internal nitridation and extrusion of Ni‐particles, while for this material the inward penetration of nitridation is relatively slow due to the low solubility and diffusivity of N in Ni and Ni‐alloys.

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Laser Nitriding of Iron, Stainless Steel, and Plain Carbon Steel Investigated by Mössbauer Spectroscopy

Schaaf

Landry

Han

et al. 2002

Industrial Applications of the Mössbauer Effect

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Einfluß von Sauerstoffzusätzen beim Gasnitrieren auf den strukturellen Aufbau von Nitrierschichten

Cited by 13 publications

References 14 publications

Microstructure of TiN coatings synthesized by direct pulsed Nd:YAG laser nitriding of titanium: Development of grain size, microstrain, and grain orientation

Microstructure of TiN coatings synthesized by direct pulsed Nd:YAG laser nitriding of titanium: Development of grain size, microstrain, and grain orientation

Nitridation in NH₃‐H₂O‐mixtures

Laser Nitriding of Iron, Stainless Steel, and Plain Carbon Steel Investigated by Mössbauer Spectroscopy

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Einfluß von Sauerstoffzusätzen beim Gasnitrieren auf den strukturellen Aufbau von Nitrierschichten

Cited by 13 publications

References 14 publications

Microstructure of TiN coatings synthesized by direct pulsed Nd:YAG laser nitriding of titanium: Development of grain size, microstrain, and grain orientation

Microstructure of TiN coatings synthesized by direct pulsed Nd:YAG laser nitriding of titanium: Development of grain size, microstrain, and grain orientation

Nitridation in NH3‐H2O‐mixtures

Laser Nitriding of Iron, Stainless Steel, and Plain Carbon Steel Investigated by Mössbauer Spectroscopy

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Nitridation in NH₃‐H₂O‐mixtures