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Erschienen in:
20.06.2019
Effect of Solid Solution Elements on Solubility Products of Carbides and Nitrides in Austenite: Thermodynamic Calculations
Erschienen in: Metallurgical and Materials Transactions A | Ausgabe 9/2019
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Abstract
To provide guidance on composition design of steel through control of the fraction of carbide or nitride precipitates in austenization, the effects of solid solution elements on solubility products of titanium, niobium, and vanadium carbides and nitrides in austenite were investigated by thermodynamic calculations using the two sublattice model. Solubility products of the carbides and nitrides in pure austenite were calculated, and the results were highly consistent with findings of previous studies. Solubility products of the carbides and nitrides in austenite containing different solid solution elements were evaluated and, in general, were also consistent with the reports of previous studies. Solubility products of titanium, niobium, and vanadium carbides and nitrides in austenite containing solid solution elements, on the condition that the total alloy content is relatively small, are given as follows:
$$ \log^{\gamma } K_{\text{TiC}} = 3.77 - \frac{8339}{T} + \left( { -\, 0.002 + \frac{14.2}{T}} \right)\left[ {\text{wt pct Mn}} \right] + \left( { -\, 0.009 + \frac{84.6}{T}} \right)\left[ {\text{wt pct Ni}} \right] + \left( {0.019 + \frac{12.3}{T}} \right)\left[ {\text{wt pct Cr}} \right] + \left( { -\, 0.017 + \frac{52.1}{T}} \right)\left[ {\text{wt pct Mo}} \right] $$
$$ \log^{\gamma } K_{\text{NbC}} = 3.72 - \frac{8534}{T} + \left( {0.004 + \frac{3.0}{T}} \right)\left[ {\text{wt pct Mn}} \right] + \left( {0.013 + \frac{35.1}{T}} \right)\left[ {\text{wt pct Ni}} \right] + \left( {0.010 + \frac{41.2}{T}} \right)\left[ {\text{wt pct Cr}} \right] + \left( { -\, 0.013 + \frac{40.4}{T}} \right)\left[ {\text{wt pct Mo}} \right] $$
$$ \log^{\gamma } K_{\text{VC}} = 4.70 - \frac{7041}{T} + \left( { -\,0.004 + \frac{18.6}{T}} \right)\left[ {\text{wt pct Mn}} \right] + \left( { - \,0.004 + \frac{37.0}{T}} \right)\left[ {\text{wt pct Ni}} \right] + \left( {0.003 + \frac{52.8}{T}} \right)\left[ {\text{wt pct Cr}} \right] + \left( { - \,0.036 + \frac{63.4}{T}} \right)\left[ {\text{wt pct Mo}} \right] $$
$$ \log^{\gamma } K_{\text{TiN}} = 4.37 - \frac{15029}{T} + \left( {0.009 + \frac{36.5}{T}} \right)\left[ {\text{wt pct Mn}} \right] + \left( { -\, 0.014 + \frac{73.4}{T}} \right)\left[ {\text{wt pct Ni}} \right] + \left( {0.004 + \frac{122.9}{T}} \right)\left[ {\text{wt pct Cr}} \right] + \left( { -\, 0.002 + \frac{37.3}{T}} \right)\left[ {\text{wt pct Mo}} \right] $$
$$ \log^{\gamma } K_{\text{NbN}} = 3.94 - \frac{10036}{T} + \left( {0.015 + \frac{25.2}{T}} \right)\left[ {\text{wt pct Mn}} \right] + \left( {0.008 + \frac{23.9}{T}} \right)\left[ {\text{wt pct Ni}} \right] + \left( { - \,0.004 + \frac{151.8}{T}} \right)\left[ {\text{wt pct Cr}} \right] + \frac{34.1}{T}\left[ {\text{wt pct Mo}} \right] $$
$$ \log^{\gamma } K_{\text{VN}} = 3.33 - \frac{8278}{T} + \left( {0.007 + \frac{40.6}{T}} \right)\left[ {\text{wt pct Mn}} \right] + \left( { - \,0.009 + \frac{26.0}{T}} \right)\left[ {\text{wt pct Ni}} \right] + \left( { - \,0.012 + \frac{163.5}{T}} \right)\left[ {\text{wt pct Cr}} \right] + \left( { - \,0.023 + \frac{57.1}{T}} \right)\left[ {\text{wt pct Mo}} \right] $$