MULTICOMPONENT BL-GROUP cBN COMPOSITES: TOOL WEAR IN NICKEL-BASE SUPERALLOY TURNING

Abstract

Superhard composite materials based on cubic boron nitride (cBN), differing in cBN content, were obtained by the method of thermobaric sintering using a toroidal type high-pressure apparatus (HPAT-30). The starting mixtures for sintering BL group composites contained 55 vol. % cBN micropowder (1–2 µm), 40 vol. %TiC (< 10 μm), or the same amount of Maxthal 312 powder (< 10 μm, nominal MAX phase Ti₃SiC₂). The remaining 5 vol. % consisted of Si₃N₄ additive (0.3–1.5 μm). Sintering was carried out at a pressure p » 8 GPa and optimal temperatures T = 2000–2050 °С for 45 s. The results of studies using X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive analysis system (EDS) indicated certain chemical reactions, phase and structural changes that occurred during thermobaric sintering of samples. In particular, the most significant changes are observed in the cBN-Ti₃SiC₂ system, where a multicomponent cBN-TiC-TiCN-TiB₂-TiSi₂ composite is formed as a result of the complete decomposition of the MAX phase. The physical and mechanical parameters (hardness, elastic modules) of the samples differed significantly from the properties of the BH group composite (BSNÔ), in which the content of cBN dominates and is ~97 vol. %. Blade processing of INCONELÒ 718 superalloy with a cutting tool from the obtained composites of the BL group when using a cooling by 8 % Sitala D 201-03 Shell emulsion is characterized by a much slower increase in cutting forces with turning time compared to BSNÔ. In addition, due to the high hardness and increased resistance of composite materials to adhesive interaction with Inconel, the development of such macrodefects as grooves is significantly restrained. The effect is especially pronounced when using a tool made of a composite based on the cBN-TiC system.