Orenburg State University, Orenburg, Russia:

S. I. Bogodukhov, Dr. Eng., Prof., Dept. of Materials Science and Technology, e-mail: ogu@mailgate.ru
E. S. Kozik, Cand. Eng., Associate Prof., Dept. of Materials Science and Technology, e-mail: ele57670823@yandex.ru
E. V. Svidenko, Cand. Eng., Associate Prof., Dept. of Materials Science and Materials Technology, e-mail: tzvetkova.katia2016@yandex.ru

The results of the study are presented on the effect of heat treatment in salt baths, bathtubs of silver Ø10 mm rods from R6M5 high-speed steel on the microstructure, carbide size, mechanical and resistance properties, fracture fractography and mass analysis of elements. Heat treatment of a tool made of high-speed steel was carried out, including the first hardening from a temperature from 1000 °C to 1100 °C, the second standard hardening and tempering according to the regime: heating (100 % BaCl₂) 1100 °C–2.5 min; air-water cooling; preheating 1050 °C (100 % BaCl₂)–1.5 min; final heating 1220 °С–1240 °С (100 % BaCl₂) / 1.5 min, then tempering 580 °С (Н-495) / 10 min, followed by cooling in air; cooling in air + water; tempering 580 °С (Н-495)–10 min followed by cooling in air and air-water flow, washing. Vickers hardness was determined for high-speed steel, and the microstructure and fine structure were studied. An analysis of the data of individual hardness measurements (НV) showed that the minimum carbide size after heat treatment decreased by 21 %, and the maximum by 12 %. The minimum size of objects after heat treatment decreased by 50 times, and the maximum size increased by 8 times, which indicates the process of grinding carbide particles. An analysis of the microstructure of R6M5 high-speed steel after various thermal conditions showed the presence of 2 phases: carbide grains and martensite. After heat treatment and the finished process, the drills are subjected to resistance tests. Conducted thermal hardening of high-speed steel P6M5 showed an increase in performance by 4 times, which indicates the effectiveness of heat treatment in salts. 

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