OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 Ta b l e 5 Results of tribotechnical tests No. Friction pair (hob – shaft) Friction coefficient Weight wear, g Total wear, g Hob Shaft 1 SCh35 – 0.3C-Cr-Mn-Si(high quality) 0.11–0.13 0.11 0.84 0.95 2 ChMN-35M – 0.3C-Cr-Mn-Si(high quality) 0.10–0.12 0.15 0.45 0.60 3 SChKM-45 – 0.3C-Cr-Mn-Si(high quality) 0.10–0.12 0.10 0.43 0.53 4 SCh35 – 0.2C-Mn(cast) 0.11–0.13 0.24 0.86 1.10 5 ChMN-35 – 0.2C-Mn(cast) 0.11–0.12 0.23 0.60 0.83 6 SChKM-45 – 0.2C-Mn(cast) 0.12–0.12 0.22 0.58 0.80 7 SCh35 – 0.09C-2Mn-Si 0.13–0.14 0.40 0.45 0.95 8 ChMN-35M – 0.09C-2Mn-Si 0.11–0.12 0.24 0.66 0.90 9 SChKM-45 – 0.09C-2Mn-Si 0.11–0.12 0.20 0.55 0.75 a b c Fig. 6. Structure of fractures of cast irons after impact bending tests: a – SCh35; b – ChMN-35M; c – SChKM-45 The fractures shown in Fig. 6 have a characteristic facet structure. A morphology analysis shows that graphite inclusions played a significant role in the initiation and development of cracks. Microcracks extending deep into the material were fixed at the points where the graphite plates came to the surface. The structure of fracture surfaces of ChMN-35M is more uniform. The size of the cleavage facets is approximately 1.5 times smaller compared to SCh35 cast iron, which is explained by the more dispersed structure of the cast iron metal base [11]. The arrows in Fig. 6 indicate characteristic fracture zones of the transcrystalline mechanism of the material. The formation of fracture zones of this type can be explained by the strength properties of the
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