High-Temperature Ion Nitriding Carbide Disposable Inserts of T15K6 Brand

Abstract

High-temperature (t = 800°С) ion nitriding of carbide disposable inserts of the T15K6 brand is performed taking into account the formation of structures, phase composition, and thickness of the surface coating, ensuring an increase in their durability during cutting tests. It is revealed that hardness and microhardness increase up to 15% after such treatment, but gradually decrease to the initial values with an increase in temperature above 600°C. Bending strength increases by 27% after ion nitriding. Fractographs of cleavages of surface layers of the T15K6 hard alloy after ion nitriding for 1 and 2 h at various temperatures evidence that the cleavage over the edges is characterized by a strongly branched linear structure, while the brittle fracture pattern is observed inside the material. Areas of segments of intergrain fracture increase with an increase in the ion nitriding duration, while those of the intragrain fracture decrease. The results of an analysis of microstructures of the surface layer of the T15K6 alloy after ion nitriding show that the sizes of conglomerate carbides in the surface layer decrease with an increase in the ion nitriding temperature. The depth of the nitriding layer of the T15K6 alloy is from 1 to 7 μm. The regularities of the influence of various temporal and temperature ion nitriding modes on operational characteristics of wares made of titanium–tungsten hard alloys of the TK group are determined. An increase in hardness, microhardness, and ultimate strength with a decrease in wear when cutting carbide disposable inserts of the T15K6 brand is established at ion nitriding temperatures of 600, 700, and 800°C under isothermal holding from 1 to 8 h. It is established that the areas of intergrain fracture segments increase with an increase in the ion nitriding duration, while those of intragrain fracture decrease. It is shown that the (TixWx)(C1 – yNy) and (Co1 – xWx)(C1 – yNy) tungsten-supersaturated solid solutions are formed during ion nitriding and ternary and quaternary compounds are isolated in the surface layer.