Polycrystalline diamond

The most frequently used bit types are the roller cone or rock bit (F g. 3.8) and the polycrystalline diamond cutter or PDC bit. 

A wide range of cutting-tool materials is available. Properties, performance capabilities, and cost vary widely (2,7). Various steels (see Steel) cast cobalt alloys (see Cobalt and cobalt alloys) cemented, cast, and coated carbides (qv) ceramics (qv), sintered polycrystalline cubic boron nitride (cBN) (see Boron compounds) and sintered polycrystalline diamond tbin diamond coatings on cemented carbides and ceramics and single-crystal natural diamond (see Carbon) are all used as tool materials. Most tool materials used in the 1990s were developed during the twentieth century. The tool materials of the 1990s... 

Cemented tungsten carbides also find use as a support for polycrystalline diamond (PCD) cutting tips, or as a matrix alloy with cobalt, nickel, copper, and iron, ia which diamond particles are embedded. These tools are employed ia a variety of iadustries including mineral exploration and development oil and gas exploration and production and concrete, asphalt, and dimension stone cutting. 

Natural diamonds used for jewellery and for industrial purposes have been mined for centuries. The principal diamond mining centres are in Zaire, Russia, The Republic of South Africa, and Botswana. Synthetic diamonds are made by dissolving graphite in metals and crystallising diamonds at high pressure (12-15 GPa) and temperatures in the range 1500-2000 K [6] see section 3. More recently, polycrystalline diamond films have been made at low pressures by... 

PDC bits get their name from the polycrystalline diamond compacts used for their cutting structure. The technology that led to the production of STRATAPAX drill blanks grew from the General Electric Co. work with polycrystalline manufactured diamond materials for abrasives and metal working tools. General Electric Co. researched and developed the STRATAPAX (trade... 

Figure 4-150 shows the major components and design of the PDC bit. The polycrystalline diamond compacts, shown in Figure 4-151. The polycrystalline diamond compacts (of which General Electric s) consist of a thin layer of synthetic diamonds on a tungsten carbide disk. These compacts are produced as an integral blank by a high-pressure, high-temperature process. The diamond layer consists of many tiny crystals grown together at random orientations for maximum strength and wear resistance.

Figure 4-151. Polycrystalline diamond compacts [43A]. (Courtesy Hughes Christensen.)...

The term PDC is defined as polycrystalline diamond compact. The term TSP is defined as thermally stable polycrystalline diamond. TSP materials are composed of manufactured polycrystalline diamond which has the thermal stability of natural diamond. This is accomplished through the removal of trace impurities and in some cases the filling of lattice structure pore spaces with a material of compatible thermal expansion coefficient. 

The section describes the first lADC standardized system for dull grading natural diamond, PDC, and TSP (thermally stable polycrystalline diamond) bits, otherwise known as fixed cutter bits [55]. The new system is consistent with the recently revised dull grading system for roller bits. It describes the condition of the cutting structure, the primary (with location) and secondary dull characteristics, the gage condition, and the reason the bit was pulled. 

Hard to extremely hard competent rock formations can be drilled with turbine motors using diamond or the new polycrystalline diamond bits. 

The positive displacement motor whose performance characteristics are given in Table 4-115 is a 5 6 lobe profile motor. This lobe profile design is usually used for straight hole drilling with roller rock bits, or for deviation control operations where high torque polycrystalline diamond compact bit or diamond bits are used for deviation control operations. 

The most common frequencies in use for CVD are micro-wave (MW) at 2.45 GHz and, to a lesser degree, radio frequency (RF) at 13. 45 MHz (the use of these frequencies must comply with federal regulations). A microwave-plasma deposition apparatus (for the deposition of polycrystalline diamond) is shown schematically in Fig. 5.18 (see Ch. 7, Sec. 3.4). 

Polycrystalline diamond, the hardest material, may provide the best wear and erosion resistance material once the deposition problems are solved and it has become commercially viable (see Ch. 7). 

Hot Filament CVD (see Figure 5.2(a)) is relatively cheap and easy to operate and produces reasonable quality polycrystalline diamond films at... 

Recently Butler et al. [4] reported the deposition of nanocrystalline diamond films with the conventional deposition conditions for micrometer-size polycrystalline diamond films. The substrate pretreatment by the deposition of a thin H-terminated a-C film, followed by the seeding of nanodiamond powder, increased the nucleation densities to more than 10 /cm on a Si substrate. The resultant films were grown to thicknesses ranging from 100 nm to 5 fim, and the thermal conductivity ranged from 2.5 to 12 W/cm K. 

S. Sumiya, T. Irifune, A. Kurio, S. Sakamoto, and T. Inoue, Microstructure Features of Polycrystalline Diamond Synthesized Directly from Graphite under Static High Pressure , Jour. Mater. Sci., 39,445 (2004). 

Polycondensation, 10 189-190, 191 as an aging mechanism, 23 64 of polyamide plastics, 19 781-782 polyester formation by, 20 390-391 silicone polymerization via, 22 556-558 in the sol-gel process, 23 61-62 Polycrystalline alloys, 13 523 Polycrystalline diamond films, deposition of, 24 744-745... 

It has been reported that when Ceo is rapidly and nonhydrostatically compressed above 20 GPa at room temperature, it transforms into polycrystalline diamond [524]. Although Ceo can be considered as a folded graphite sheet, we must take into account that in the pentagons there is an important tetrahedral distortion making the transformation of Ceo into diamond likely easier than the HP-HT conversion from graphite, and it is possible to use this reaction for industrial production of diamonds. 

Cubic Phase of Boron Nitride c-BN. The cubic phase of boron nitride (c-BN) is one of the hardest materials, second only to diamond and with similar crystal structure. It is the first example of a new material theoretically predicted and then synthesized in laboratory. From automated synthesis a microcrystalline phase of cubic boron nitride is recovered at ambient conditions in a metastable state, providing the basic material for a wide range of cutting and grinding applications. Synthetic polycrystalline diamonds and nitrides are principally used as abrasives but in spite of the greater hardness of diamond, its employment as a superabrasive is limited by a relatively low chemical and thermal stability. Cubic boron nitride, on the contrary, has only half the hardness of diamond but an extremely high thermal stability and inertness. 

A table of polycrystalline diamond may be manufactured and later attached to a prosthetic joint in a location such that it will form a bearing surface. The attachment could be performed by welding, brazing, or by the use of fasteners such as screws, bolts, or rivets (17). 

Since these masses of polycrystalline diamond possess extensive diamond-to-diamond bonding, they have, in contrast to single-crystal diamond, excellent crack resistance, since any crack that begins in one crystal on an easy cracking plane (parallel to an octahedral face) is halted by neighboring crystals that are unfavorably oriented for their propagation. 

Fig. 1.2 Illustration of a stagnation-flame configuration for the deposition of a polycrystalline diamond film. The photograph of the flame itself shows a highly luminous flat flame just above the deposition surface.

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