Effect of Ce on Inclusions and Precipitates in 10Cr5MoV Steel and the Microscopic Behavior of Solid Solution Ce in Steel

Abstract

In this article, the effects of Ce (0–120 ppm) on inclusions and precipitates in industrially produced CO2/H2S‐resistant 10Cr5MoVCe special oil well pipe steel and the microscopic behavior of Ce solid solution in steel were systematically studied by scanning electron microscopy, transmission electron microscopy, electrolysis separation of nonaqueous mixed solutions, and first‐principles calculations. After adding Ce to 10Cr5MoV steel the inclusions changed from chain‐like Al2O3 inclusions to polygonal Ce–O–S–Al–Ca complex inclusions and spheroidal Ce2O3, CeAlO3, Ce2O2S, and CeS inclusions. When the total Ce content was 25–120 ppm, the solid solution Ce content was maintained at about 20% of the total Ce content. The Ce had no significant influences on the types of chromium carbide precipitates, and the chromium carbide precipitates of all tested steels were Cr23C7 and Cr7C3. However, with the increase of Ce, the content of Cr23C7 and Cr7C3 precipitates decreased slightly, from 1.27% without Ce to 1.18% when Ce was 120 ppm. The first‐principles calculation results show that there was strong interaction between Fe, Ce, and Cr. Ce enhanced the interaction force between the Fe and Cr atoms, and improved the stability of the system, which facilitated the solid solution of Cr in the Fe–Cr system.