Effect of Solid Solution Elements on Solubility Products of Carbides and Nitrides in Austenite: Thermodynamic Calculatio
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8534 3:0 35:1 þ 0:004 þ ¼ 3:72 ½wt pct Mn þ 0:013 þ ½wt pct Ni T T T 41:2 40:4 ½wt pct Cr þ 0:013 þ ½wt pct Mo þ 0:010 þ T T
7041 18:6 37:0 þ 0:004 þ ½wt pct Mn þ 0:004 þ ½wt pct Ni logc KVC ¼ 4:70 T T T 52:8 63:4 ½wt pct Cr þ 0:036 þ ½wt pct Mo þ 0:003 þ T T 15029 36:5 73:4 þ 0:009 þ ½wt pct Mn þ 0:014 þ ½wt pct Ni logc KTiN ¼ 4:37 T T T 122:9 37:3 ½wt pct Cr þ 0:002 þ ½wt pct Mo þ 0:004 þ T T c
log KNbN
10036 25:2 23:9 þ 0:015 þ ¼ 3:94 ½wt pct Mn þ 0:008 þ ½wt pct Ni T T T 151:8 34:1 ½wt pct Mo ½wt pct Cr þ þ 0:004 þ T T
XUAN-WEI LEI, XUE-HUI ZHANG and TONG-XIANG LIANG are with the School of Materials Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, P. R. China. Contact e-mails: [email protected]; [email protected] DA-YONG LI is with the Bohai Shipyard Group Co., Ltd., Huludao 125000, P. R. China. Manuscript submitted December 23, 2018. Article published online June 20, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
VOLUME 50A, SEPTEMBER 2019—4445
c
log KVN
8278 40:6 26:0 þ 0:007 þ ¼ 3:33 ½wt pct Mn þ 0:009 þ ½wt pct Ni T T T 163:5 57:1 ½wt pct Cr þ 0:023 þ ½wt pct Mo þ 0:012 þ T T
https://doi.org/10.1007/s11661-019-05295-w The Minerals, Metals & Materials Society and ASM International 2019
I.
INTRODUCTION
THE addition of strong carbide- or nitride-forming element of titanium, niobium, or vanadium to microalloyed low carbon steels can generally improve their overall mechanical properties owing to formation of fine compound precipitates in the matrix. The fraction of such precipitates strongly influences the performance of the steel. Solubility product of a compound in iron is an essential concept that can be used to calculate its fraction. Solubility products of carbides and nitrides in austenite can be determined by experimental measurements[1,2] or estimated by thermodynamic calculations.[3,4] The errors associated with experimental measurements are strongly dependent on the experimental process and accuracy of detection of the experimental equipment. In contrast, theoretical work based on computer coupling of phase diagrams and thermochemistry (CALPHAD) can interrelate multiple data from different sources including experimental measurements. Optimized thermodynamic parameters can minimize experimental errors that impede the performance of experimental measurements. The optimization process in CALPHAD depends on assessment of the experimental measurement data, but generally speaking, the solubility products determined by thermodynamic calculations are close to, but more convincing than, those obtained by experimental measurements. Owing to recent developments in CALPHAD, considerably more thermodynamic parameters for carbides and nitrides in iron have been determined, thus enabling comprehensive study of solubility products of carbides and nitrides in austenite. Popov and Gorbachev analyzed solubilities of vanadium carbide and nitride,[5] niobi
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