Vol 40, No 5 (2018)

Basic achievements of the Bakul Institute for Superhard Materials in the field of synthesis and sintering of superhard materials at extremely high p-T parameters while being in the composition of the National Academy of Science of Ukraine are presented.

The investigations performed at high pressures and high temperatures (HTHP crystallization) have permitted clarifying the mechanism of phase transformations and carbon transport in solvent metals for diamond growth and elaborating methods for growing large-size structurally perfect diamond single crystals of types Ib, IIa, and IIb. The findings have provided the basis for the process of production of diamonds for applications in electronics, laser technology, precision machining operations, well drilling tools. The use of a large-volume six-punch high pressure apparatus makes it possible to grow diamond single crystals with a higher efficiency. It is estimated that this apparatus is capable of producing annually at least 1 mln carats of structurally perfect crystals of required types for various applications.

Based on the analysis of published studies, thermodynamic functions describing the processes of the formation of intercarbide and interface surfaces during the solid- and liquid-phase sintering of WC–Co cemented carbides. At present a certain progress in studies of the structure and composition of intercarbide WC/WC and interface WC/Co surfaces is attained, the technologies are developed that allow affecting the composition and structure of these surfaces. It is noted that the composition and structure of intercarbide and interface surfaces (Ti, W, Ta)C–WC–Co and (Ti, W, Nb)C–WC–Co of cemented carbides are not adequately investigated. The studies on the influence of the composition and structure of intercarbide and interface surfaces on physico-mechanical properties of cemented carbides and their operational characteristics remained urgent.

The paper reviews the latest advances in the development of abrasive tools and investigation of diamond abrasive machining processes. The review demonstrates the necessity of taking into account the interaction between abrasive and workpiece materials as well as the influence of elements of a workpiece material on wear of abrasive grains; also, it shows the importance of sorting diamond grains by shape, especially within a wide range of their strength. Special features of application of CVD diamonds and the methods for changing the diamond–bond interface zone in order to improve grain retention are discussed.

The publications addressing the diamond tools for drilling oil and gas vertical and controlled directional wells are reviewed. The performance of diamond drilling tools of various functionalities is assessed by drilling in soft and medium hard formations. Rock destruction tools of different designs, which are fitted with novel thermally stable and wear-resistant diamond-containing composites, are compared with similar tools of earlier models. The main factors responsible for premature tool wear in medium and hard formations at increased speeds are discussed. Some promising areas in the development and application of diamond drilling tools are identified.