1 - 5 October 2017

Milan, Italy

Diamond and Superhard Materials, Manufacturing and Applications

Session Chairs:

Prof Dr Igor Konyashin (Element Six GmbH, Germany)
Dr Stuart Nailer (Hilti Corporation, Liechtenstein)

Some sixty years after its frst successful synthesis, the lustre of diamond as the hardest industrial material remains undimmed. In its diverse particulate and composite forms, diamond continues to offer unmatched performance in applications from fne polishing and rock drilling through to precision machining.

Catering for both the casual listener and the specialist, this seminar aims to provide a comprehensive overview of the manufacture, application and behaviour of diamond and its related superabrasive, cubic boron nitride. Consequently, the seminar features presentations from industrial and academic experts, providing experimental and computational insights into polycrystalline and particulate (‘grit’) superabrasive materials and their respective defned and undefned abrasive processes.

The seminar will begin with an introduction to superhard materials and their latest advances and continue with performance studies of these materials in such diverse applications as the machining of aerospace alloys and the coring and sawing of construction materials. Complementing these industrial insights with academic research, the seminar presents investigations into diamond wear on an atomistic level, and concludes with the latest research into such felds as binderless polycrystalline superhard materials and protective coatings for diamond cutting tools.


Synthetic Diamond and Superhard Materials: State of the Art
Dipl. -Ing. Bernd Ries (Element Six GmbH, Germany); Prof  Dr Igor Konyashin (Element Six GmbH, Germany / National University of Science and Technology MISiS, Russia)

An introduction to synthetic diamond, superhard materials and their latest advances will be given. The history of the invention of synthetic diamond and cubic boron nitride (c-BN) manufacturing processes at high temperatures and ultra-high pressures as well as that of chemically vapor deposited (CVD) diamond will be briefly reported. The state of the art in the field of the fabrication of synthetic diamond and cubic boron nitride grits at high-pressure high-temperate conditions will be described. The production of polycrystalline diamond films and large diamond single- crystals by CVD at low pressures will presented. The state of the art in the field of the fabrication of polycrystalline diamond (PCD) layers on cemented carbide substrates will be reported. Major applications of synthetic diamond and superhard materials on the basis of diamond and c-BN will be briefly outlined. The extreme properties of diamond and c-BN based superhard materials make them ideal for a surprising variety of advanced applications in industry, science and the home.

 

High Performance Machining of Aerospace Alloys with Ultrahard Cutting Tool Materials
Dr Rachid M'Saoubi (Seco Tools AB, Sweden)

Abstract: The surface integrity and functional performance of machined components are closely related to the characteristics of the part produced, in terms of the surface topography and the metallurgical and mechanical state of the subsurface layers. In Nickel-based super alloys (e.g. Inconel 718) and Titanium alloys (e.g. Ti6Al4V), materials commonly used for rotating parts in medium-high temperature sections of aero engine components, the critical importance of controlling surface integrity produced by machining has been highlighted in several investigations. Typically, uncoated and coated cemented carbide are often preferred for medium finish/finish machining applications where acceptable surface integrity requirements need to be achieved and low cutting speeds are usually employed for maintaining a reasonable tool performance for the cemented carbide. With the development of ultra hard cutting tools such as polycrystalline cubic boron nitride (PCBN) and polycrystalline diamond (PCD), possible alternatives to cemented carbide in finishing of superalloys and Titanium alloys have emerged and productivity gains could therefore be achieved due to higher cutting speeds employed. This presentation will come some recent advances in ultrahard cutting tools materials development and associated high performance cutting technologies for successful machining of Titanium and Nickel based alloys.

 

Diamond Technologies for Construction Applications
Dr Stuart Nailer; Dr S. Huth; Dr Steven Moseley; Mr T. Klein; Dr S. Grasberger (Hilti Corporation, Liechtenstein)

More than sixty years after its realisation, synthetic diamond remains the material of choice for the sawing and core drilling of demanding construction materials such as heavily-reinforced concrete. In these applications, synthetic diamond is mostly used in particulate “grit” form within metal matrix segments, whilst polycrystalline diamond cutters may also be utilised in high-performance insert tools for niche purposes. Despite synthetic diamond being well-established, diamond systems in construction applications attain ever-higher levels of performance. These derive not only from increased capabilities of the power tools, but also from advances in the technologies underpinning diamond “inserts” (core bits, saw blades).This presentation provides an overview of the use of diamond technologies in the construction industry as well as insights into the latest advancements, with a principal focus on diamond inserts. An introduction to common construction applications, tools and base materials is provided, together with their consequent requirements of the diamond inserts. Insights into developments in the design, materials and manufacture of diamond-impregnated segments are given, and the wear and fracture behaviours of diamond particles under different operating conditions are discussed

 

Atomistic Understanding of Friction and Wear in Diamond
Prof Dr Micael Moseler (Fraunhofer IWM, Germany)

Although friction and wear in diamond systems is of importance in machining of rocks and non-ferrous materials as wells as in diamond-coated bearing systems, the underlying atomic-scale mechanisms remain elusive. Here, molecular dynamics simulations are presented revealing various friction regimes of dry and water-lubricated diamond surfaces. While extreme water starvation results in cold welding and anisotropic amorphization, already small traces of water can establish ultralow friction by mechanically inducing aromatic reconstructions that prevent formation of covalent bonds between diamond surfaces. For increased humidity, dissociative chemisorption of water molecules (frequently assisted by Grotthuss-type proton transport) results in another ultralow friction regime. The last part of the lecture addresses the mechano-chemistry during dry sliding of diamond with oxides surfaces.

 

New Horizons for Diamond Cutting Tools Industry: Mechanical Alloying, Disperse Strengthening, Self-Assembled Protective Coatings
Dr Daria A. Sidorenko, Dr P.A. Loginov; Prof Dr E.A. Levashov (National University of Science and Technology MISiS, Russia)

Diamond tools are widely used to machine the most difficult-towork-with materials. Conventional method for production of diamond tool binders is co-precipitation of metal hydroxides. As a new solution, we applied an innovative approach for binder and tool fabrication.Firstly, we utilized high-energy ball milling of the elemental powders, which provided production of mechanically alloyed materials with solid solution strengthening effect.Secondly, binders were modified with WC, ZrO2, h-BN nanoparticles, CNTs, etc., which led to significant improvement of mechanical and tribological properties.Thirdly, a new phenomenon of spontaneous WC-based coating formation on diamonds during sintering of composite contained WC nanoparticles was observed.Reinforced concrete drilling tests showed that introduction of nanoadditives into standard binders led to increase in tool life up to 2-4.5 times and cutting speed up to 50%. Comparative tests of diamond wheels and wire saws with modified binder demonstrated increase in tool life and productivity up to 2 times during cutting of cast iron and steel.Simultaneous enhancement of binder mechanical and tribological properties and formation of adhesive coatings on diamonds facilitate a synergistic effect, which results in increased performance.

 

Binderless nanopolycrystalline diamond and cBN - High Pressure Synthesis, Properties and Emerging Applications
Dr Marcus Schwarz (TU Bergakademie Freiberg, Germany)

The use of ceramic or metallic binder systems was and is the main road for industrial production of superhard materials based on diamond and cBN. The binders act as sintering aids, helping to decrease HP/HP parameters for sintering. The plasticity of a metal component provides toughness and mechanical damage tolerance to a cutting insert, while certain ceramic additives can retard tribochemical reactions with the workpiece. However, for machining of modern construction materials such as fiber-reinforced composites, the softer binder phase often is the "weak link", where degradation and failure start. In other cases, such as ultraprecision machining, the microstructure of a sintered composite would be simply to coarse. Nanopolycrystalline diamond (NPD) and c-BN (ncBN) are formed via direct conversion from graphite and h-BN without any additive or binder at very high pressures between 10 and 20 GPa. Industrialization of these extraordinary materials will therefore impose new challenges to the quality and lifetime of the tungsten carbidebased high pressure tools required for their synthesis. This talk gives an overview on recent trends and findings in the high pressure synthesis of NPD and ncBN and their potential use for precision machining, wire drawing and other applications.

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