Precipitation Thermodynamics of TiN in B439M Ferritic Stainless Steel during Solidification

doi:10.3901/JME.2020.18.073

Abstract

Abstract: The precipitation thermodynamic of TiN in ferritic stainless steel has been extensively researched. However, few works referring to the thermodynamics of TiN precipitation heterogeneously is performed. Thermodynamic calculation of TiN shows that TiN does not precipitate during the melting process in B439M ferritic stainless steel. During solidification, the content of Ti and N in the liquid is increased by 7.4 and 3.2 times the initial composition at the end of solidification. The EDS mapping and thermodynamics calculations of MgO and Al₂O₃ show that the Mg-Al spinel (MgO·Al₂O₃) will form preferentially in the melts. As a result, the composite inclusion can be observed in the microstructure. First, TiN can nucleate heterogeneously with MgO and Al₂O₃ oxides acting as heterogeneous sites. Then, NbC will nucleate with TiN as the core to form the composite include, which is in agreement with the calculated results. This can provide experimental evidences that in ferritic stainless steels, Ti tends to combine with N to form TiN, and Nb is prone to combine with C to form NbC.

Key words: B439 Ferritic stainless steel, TiN inclusion, solidification precipitation, thermodynamics analysis

CLC Number:

TG142

DONG Xuguang, FU Junwei. Precipitation Thermodynamics of TiN in B439M Ferritic Stainless Steel during Solidification[J]. Journal of Mechanical Engineering, 2020, 56(18): 73-80.

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