| Summary: | Nitride and carbide are the second phases which play an important role in the performance of bearing steel, and their precipitation behavior is complicated. In this study, TiN-MC<i><sub>x</sub></i>precipitations in GCr15 bearing steels were obtained by non-aqueous electrolysis, and their precipitation mechanisms were studied. TiN is the effective heterogeneous nucleation site for Fe<sub>7</sub>C<sub>3</sub> and Fe<sub>3</sub>C; therefore, MC<i><sub>x</sub></i>can precipitate on the surface of TiN easily. The chemistry component of MC<i><sub>x</sub></i> consists of M<sub>3</sub>C and M<sub>7</sub>C<sub>3</sub> (M = Fe, Cr, Mn) and Cr<sub>3</sub>C<sub>2</sub>. TiN-MC<i><sub>x</sub></i> with high TiN volume fraction, TiN forms in early stage of solidification, and MC<i><sub>x</sub></i> precipitates on TiN surface after TiN engulfed by the solidification advancing front. TiN-MC<i><sub>x</sub></i> with low TiN volume fraction, TiN and MC<i><sub>x</sub></i> form in late stage of solidification, TiN can not grow sufficiently and is covered by numerous precipitated MC<i><sub>x</sub></i>particles.
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