Effect of Transient Reoxidation on Inclusions in Rare‐Earth‐Treated Bearing Steel

Abstract

The impact of transient reoxidation environments on the chemical morphology evolution of nonmetallic oxide inclusions in rare‐earth‐treated bearing steel is investigated using FactSage thermodynamic simulation calculations, vacuum induction furnace experiments, and high‐temperature laser confocal microscopy experiments. Thermodynamic calculations indicate a direct correlation between the initial rare‐earth content and the oxygen required to transform Ce2O2S to CeAlO3 during secondary oxidation. Furthermore, a higher initial rare‐earth content leads to a more extensive and complete conversion to CeAlO3. Vacuum induction furnace experiments reveal that the inclusions transform from Ce2O2S to CeAlO3 and Al2O3 and eventually into composite oxide clusters. This results in a significant increase in inclusions, with near‐spherical Ce2O2S inclusions transforming into aggregated CeAlO3, leading to an increase in the average inclusion size from 2.4 to 4.2 μm. Laser confocal scanning microscopy experiments show that CeAlO3 exhibits a higher tendency to aggregate than Ce2O2S inclusions, the primary factor contributing to the observed increase in the average inclusion size after secondary oxidation. The results of this study provide theoretical guidance for mitigating the adverse effects of rare‐earth secondary oxidation on bearing steels, particularly in terms of inclusion control.