Investigations of the adjustment of nitrogen and carbon in the {epsilon}-phase
- Freiberg Univ. of Mining and Technology (Germany)
The phase field of {epsilon}-(carbo)nitride together with its equilibrium solubility of nitrogen and carbon can be calculated by thermodynamic models as a function of the temperature and the nitriding potential K{sub N} = {var_phi}(NH{sub 3})/{var_phi}(H{sub 2}) and carburizing potential K{sub c} = {var_phi}(CO){var_phi}(H{sub 2})/{var_phi}(H{sub 2}O). The results are presented in the form of modified Lehrer diagrams. The calculations show that a non-coupled adjustment of nitrogen and carbon is possible in the {epsilon}-phase by a suitable choice of the nitriding and carburizing potential. However, the experimental adjustment of the interstitials in the {epsilon}-phase is not satisfactory. Therefore, iron foils (thickness: 10 {micro}m) were nitrided in retort-type furnaces (150 liters) with precisely controlled atmospheres. The gas mixtures were controlled by gas chromatographic analysis and oxygen probes. The complete transformation of the iron foils into the {epsilon}-(carbo)nitride was controlled by X-ray analysis. The nitrogen and carbon concentrations in the {epsilon}-phase were determined by chemical analysis. The experimental results are in good agreement with the calculations. The investigations of nitrided specimens allow conclusions for the production of compound layers with various nitrogen and carbon concentrations by the purposeful adjustment of the nitriding and carburizing potential. This is of interest for the corrosion and wear resistance of nitrided components.
- OSTI ID:
- 389758
- Report Number(s):
- CONF-951222--; ISBN 0-87170-561-3
- Country of Publication:
- United States
- Language:
- English
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