OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 a b c Fig. 17. The fatigue crack on the sample surface: a – image obtained by light microscopy; b, c – images obtained by synchrotron radiation computed laminography [38] MnS inclusions. Manganese sulfide inclusions are oriented perpendicular or parallel to the sample surface. Before testing, the samples were annealed with heating at 1,103 K for 0.5 h and then tempered at 453 K for 2 h. Ceramic balls 6.0 mm in diameter with a Young’s modulus of 300 GPa were used as indenters. The indenter performed multiple reciprocating movements over the sample surface. The length of the resulting friction track was 3.0 mm (Fig. 19) [39]. This paper presented the results recorded at the maximum Hertzian stress pmax = 5.39 GPa. The works allowed drawing the conclusions about the duration of the initiation and propagation processes of vertical and horizontal cracks, as well as about the effect of the size and orientation of MnS inclusions on the processes of pitting in ball-bearing steel. The images of defects recorded by the laminography method made it possible to assess the nature of the material destruction at various stages of testing the samples. The analysis carried out by the authors of papers [39–41] indicates the effectiveness of the application of the computed laminography method using synchrotron radiation when studying the processes of contact fatigue loading of metals. Ta b l e 4 Composition of bearing steel (wt. %) C Si Mn P S Cr Fe 1 0.35 0.47 0.006 0.02/0.049 1.5 Rest Fig. 18. Schematic of a contact-fatigue test setup [40]
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