Understanding the Effect of Heat Treatment Involving Heating in Hydrogen Medium on the Properties of Т15К6 Grade Hard Alloy
This research examined the effect of different cooling media applied during heat treatment on the physico-mechanical properties and performance (hardness and back side wear) of parts made of hard powder alloy. The study looked at clamp-on five-sided indexable inserts per GOST 19065-80 made of Т15К6 grade double hard alloy. Characterization was done with the surface layer on and after it had been removed. Heat treatment in chlorine-barium baths had almost no effect on the weight of the specimens. Quenching and tempering in nitre baths may lead to partial dissolution of hard alloys. For this reason, measurements were taken to determine the weight loss in the specimens. The specimens were subjected to single-step hardening and salt-bath isothermal quenching. The following variation ranges were applied in the case of single-step hardening: heating temperature - from 950 to 1,150<sup>о</sup>С; cooling rate - from 10<sup>о</sup>С/sec (air) to 110<sup>о</sup>С/sec (oil); tempering temperature - from 200 to 600<sup>о</sup>С; tempering cycles - from 1 to 3, the time of each cycle being 15 min. Analysis of the heat-treated inserts indicate that structural changes take place in them during heat treatment. When the inserts were heated to 1,300 and 1,450<sup>о</sup>С, the h-phase was observed in them. The cutting properties of the inserts were determined by cutting on a 6Н11 vertical milling machine. A 100 mm face cutter was used, and the test inserts were clamped. The heat treatment induced changes in the properties of hard alloys established through the above experiments can be linked to either the changing phase composition of the alloy or the composition of the binding phase or some finer changes in the structure of the carbide phase responsible for wear resistance.