Influence of surface decarburization on precipitated phase of high nitrogen stainless bearing steel
A decarburization and denitrification layer will be formed on the surface of X30N high nitrogen stainless bearing steel after heat treatment.In order to investigate the influence of local composition chan-ges of C and N on the precipitation of secondary phases in the material,the precipitated phases were separa-ted from the matrix by electrolytic extraction using 10 g/L lithium chloride-40 g/L sulfosalicylic acid-5％(V/V)glycerol methanol solution.The structure and morphology of precipitated phases were studied by X-ray diffraction(XRD)and scanning electron microscope(SEM).The elemental contents in precipitated pha-ses were measured using carbon-sulfur analyzer,nitrogen analyzer and inductively coupled plasma atomic e-mission spectrometer(ICP-AES).The results showed that the main types of precipitated phases in the test steel were M23C6 and Cr2(C,N).The decarburized surface was dominated by Cr2(C,N).With the increase of the depth from the decarburized surface,the diffraction spectrum peak of M23C6 was gradually obvious.The total content of precipitated phases gradually increased,and basically reached stability at 0.4 mm be-low the decarburized surface.The content of C increased by 460％compared to the surface of decarboniza-tion layer.Meanwhile,the content of N increased by 38.9％,and the content of total precipitated elements increased by 85.2％compared to the surface of decarbonization layer.The morphology of Cr2(C,N)was mainly in spherical particles,and the morphology of M23C6 was mainly in irregular short rods.
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