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DS: Dünne Schichten

DS 6: Laserverfahren III

DS 6.2: Fachvortrag

Montag, 27. März 2000, 15:45–16:00, H31

Stability of laser produced iron nitrides tested by annealing treatments — •M. Han, F. Landry, E. Carpene, K.-P. Lieb, and P. Schaaf — II. Physikalisches Institut der Universität Göttingen, Bunsenstrasse 7/9, D-37073 Göttingen

Laser nitriding is very effective to improve the mechanical properties, surface hardness, corrosion and wear resistance of iron and steel, with the advantages of high nitrogen concentration, fast treatment and accurate position control without any undesired heating effect of the substrate [1-4]. The stability of the laser produced iron nitrides is still under investigation. In this article, the thermal stability of the iron nitrides is investigated by annealing treatments, which are conducted in vacuum and air respectively. The phase composition of the nitride layer is deduced from Conversion Electron Mössbauer Spectroscopy (CEMS), Resonant Nuclear Reaction Analysis (RNRA) and Grazing incidence X-ray Diffraction (GXRD). The surface hardness is measured by nanoindentation methods. We find two critical temperatures for iron annealed in vacuum: at 250^∘C, the predominant γ phase changed totally into γ’ phase, and when the temperature exceeds 500^∘C, all of the nitrogen has escaped from the surface layer, resulting in pure α phase. This is compared to the annealing treatments in air.

[1] P. Schaaf, F. Landry, K. P. Lieb; Appl. Phys. Lett. 74(1999) 153

[2] F. Landry, K.-P. Lieb, P. Schaaf; J. Appl. Phys. 86 (1999) 168

[3] C. Illgner, P. Schaaf, K.-P. Lieb, R. Queitsch, J. Barnikel; J. Appl. Phys. 83 (1998) 2907

[4] P. Schaaf; Advances in Solid State Physics 39 (1999) 561