High-temperature ion nitriding of T15K6 indexable carbide inserts

High-temperature (t = 800 °С) ion nitriding of T15K6 indexable carbide inserts was carried out with regard to the structure formation, phase composition, surface coating thickness ensuring an increase in their durability during the cutting test. It was found that hardness and microhardness values increase to 15 % after ion nitriding, however, with a temperature increase of more than 600 °C they gradually decrease to their initial values. Flexural strength after ion nitriding increases by 27 %. The fractography of fractures in the T15K6 carbide surface layers after ion nitriding for 1 and 2 hours at different temperatures showed a very branched fracture structure on edges with a fragile pattern inside the material. The analysis of T15K6 carbide surface layer microstructures after ion nitriding showed that as the ion nitriding temperature increases, the size of conglomerate carbides in the surface layer decreases. The depth of the T15K6 nitrided layer is 1 to 7 pm. Certain regularities of the effect of various ion nitriding time and temperature conditions on the performance characteristics of products made of TK group titanium-tungsten alloys are determined. At 600, 700, 800 °C ion nitriding temperatures and 1 to 8 hours isothermal exposure time, the increase in hardness, microhardness and tensile strength with lower wear was found when cutting T15K6 indexable carbide inserts. It is determined that as the ion nitriding time increases, intergranular destruction areas expand, while the intragranular areas shrink. In case of ion nitriding, a solid solution (Ti_xW_x)(C_{1_y}N_y) and (Co_{1_x}W_x)(C_{1_y}N_y) supersaturated with tungsten is formed and three and four component compounds are released in the surface layer.

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