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Structure and properties of superhard cBN composites with a nanostructured binding

Tetiana A. Garbuz 

V. Bakul Institute for Superhard Materials NAS of Ukraine, 2, Autozavodska str., Kiev 04074, Ukraine


The process for obtaining PCBN composites by the reaction sintering powders cBN with Al at pressures of 7.7 and 4.2 GPa with a preliminary dispersion of Al in the mixture at p = 2.5 GPa and T = 1300 K is designed in the ISM NASU. The problems of sintering nanopowders cBN are following: high cohesive activity, tendency to a phase transition cBN→hBN; difficulty infiltration due to the small size of the pores. cBN submicron powder advisable used in the mixture cBN-Al, in submicron cBNthe 15 % nanofraction located on the surface of larger particles. Nanosized particles before others interacted with Al. The reaction product AlN inherit the size and morphology of nanoparticles cBN. Instead of a continuous frame cBN, resulting in sintering micron, highly dispersed structure of phase cBN in the shell with AlN nanoscale grains (15-30 nm) is formed. The material has a high fracture toughness - 10.5 MPa∙m1/2 at a hardness 27 GPa.

Nanocomposites system cBN-Al-TiB2 were obtained by the same principle, where a high modulus TiB2 in the mixture acts as an activating, alloying and modifying additives. Here nanophases were the reaction products - solid solutions Ti x Al 1-x B 2 (5-200 nm), Al x B y N z (≤ 100 nm) and on the boundary between cBN and Ti x Al 1-x B 2 formed Ti68B10N22 (≤ 30 nm). Structure of composite with strain hardening frame cBN and high modulus nanostructured binding formed in the nanocomposite cBN-Al-TiB2. The new composite has Knoop hardness 34-35 GPa and fracture toughness 6.5 MPa∙m1/2.

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Presentation: Poster at Nano and Advanced Materials Workshop and Fair, by Tetiana A. Garbuz
See On-line Journal of Nano and Advanced Materials Workshop and Fair

Submitted: 2013-06-05 15:47
Revised:   2013-06-05 15:47