OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 7 2 5 can be seen on the surface of the micro-crater near the cutting edge, already passing perpendicular to the rake surface. Their character indicates their thermal nature: near the cutting edge, the insert heats up much faster and more than when moving away from it, which leads to the appearance of thermal micro-cracks. At magnification (Fig. 6, d), a black cavity is observed on the surface of the micro-crater, which indicates the tearing out of a ceramic particle of about 20 µm in size. A thermal crack passing through this area indicates a possible weakening of the tool material due to a sharp temperature drop. Let us consider some features of wear of ceramic cutting inserts on which a chamfer was forcibly formed (Table 4). On the contact surfaces of the cutting insert, areas without traces of significant wear are recorded, and minor adherence of the workpiece material is observed only near the cutting edge (Fig. 7, a). No traces of abrasive wear are observed. In this regard, it seems advisable to continue research in the part of using Y-TZP-Al2O3 cutting ceramics for dry high-speed turning and milling of hardened and difficult-to-machine materials, as well as to conduct research on comparative resistance tests with a study of the roughness of the workpiece surfaces. Ta b l e 4 Results of tests in stage 2 No. Cutting speed V (m/min) Feed rate S (mm/rev) Cutting depth t (mm) Cutting distance L* (mm) Note 1 200 0.25 0.1 3300 no edge chipping, oxidized chip Fig. 7. Typical micrographs of wear and failure areas of ceramic cutting inserts with a chamfered cutting edge: а – general view; b – crater on the rake face; c, d – elemental mapping а b c d
RkJQdWJsaXNoZXIy MTk0ODM1