OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 7 2 5 Ta b l e 3 Results of tests in stage 1 No. Cutting speed V (m/min) Feed rate S (mm/rev) Cutting depth t (mm) Cutting distance L* (mm) Note 1 200 0.05 0.2 50 edge chipping, chip burning 2 300 0.4 5 3 400 0.1 10 4 0.1 5 5 200 0.4 50 edge chipping, oxidized chip 6 0.25 60 7 600 10 edge chipping, chip burning 8 100 50 edge chipping, increased vibrations 9 0.1 edge chipping, low surface roughness 10 200 0.4 100 11** 0.25 600 edge chipping *L – path until catastrophic wear (cessation of chip formation) ** – data from 4 repetitions. a b Fig. 5. Cutting process fragment with the formation of spiral (a) and burning (b) chips at cutting speeds of 200 and 400 m/min, respectively After the expected wear value had been reached, when the cessation of chip formation due to chipping was visually recorded, the insert was rotated clockwise, which made it possible to observe different stages of wear on the same cutting insert (Fig. 6, a, zone 1), i.e. the right part of the worn surface was rotated clockwise (Fig. 6, a, zone 2). The wear of the cutting insert begins to manifest itself in the form of a crater up to 1.1 mm long (Fig. 6, a, zone 1) on the rake surface. It is closely adjacent to the cutting edge and goes over to the main back surface (Fig. 6, a, zone 1). In this case, it is not so much wear that occurs (therefore, it is generally incorrect to speak about wear), as brittle fracture (delamination) of a radial shape along surfaces parallel to the rake surface. This is due to the action of tangential stresses, the greatest value of which is located slightly below the rake surface [26]. The zone of delamination of the cutting material passes far
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