Abstract
In this paper, a numerical and experimental study of the nitrogen concentration profile in the precipitation layer of gaseous nitrided 16MnCr5 alloy steel was performed. The gaseous nitriding was performed in ammonia atmosphere at 510, 550 and 590°C, and for each temperature four different nitriding times were chosen. Nitrogen concentration profile of the nitrided specimens was experimentally investigated with electron probe microanalysis and modeled with finite element method through ANSYS finite-element software package. The model was coded in ANSYS Parametric Design Language, and the validity of the model was demonstrated by comparison with experimental data. The accuracy of the proposed model makes it a valuable tool in complementing the experimental investigations on gaseous nitriding of 16MnCr5 and similar alloy steels. Key words: Finite element method, nitrogen profile, 16MnCr5, ANSYS, electron probe microanalysis (EPMA).
Highlights
Nitriding is an industrial thermochemical surface treatment process, usually carried out at temperatures ranging from 500 to 590°C, by which the surface of various steel materials is enriched with nitrogen that is introduced through a nitrogen donating species
Nitrogen concentration profile of the nitrided specimens was experimentally investigated with electron probe microanalysis and modeled with finite element method through ANSYS finite-element software package
During gaseous nitriding the ammonia gas under the influence of the process temperature dissociates at the surface of steel and subsequently followed by atomic nitrogen diffusion into the ferrite matrix
Summary
Nitriding is an industrial thermochemical surface treatment process, usually carried out at temperatures ranging from 500 to 590°C, by which the surface of various steel materials is enriched with nitrogen that is introduced through a nitrogen donating species. Time (h) 4 9 16 36 steel and depending on the process parameters it may be subdivided into two layers: A compound layer at the surface consisting mainly of iron nitrides ( Fe2 3N and ' Fe4N ) and a precipitation layer underneath the compound layer composed of interstitially dissolved nitrogen in combination with nitrides of alloying elements (Emami et al, 2010; Günther et al, 2004; Hosmani et al, 2008; Jung, 2011; Schacherl and Mittemeijer, 2004; Selg, 2012; Somers et al, 1989; Syla et al, 2010). A comprehensive finite element model should be time and cost effective, reduce considerably the number of experimental investigations, and in case of nitriding for example should be adjusted to include or fit various geometries, steels and a wide range of process parameters. Finite element method (FEM) was used to model the nitrogen concentration profile in the precipitation layer (diffusion zone) of gaseous nitrided 16MnCr5 alloy steel. The model can be customized very to include other alloy steels similar to 16MnCr5
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