Manufacture of drill bits from new diamond materials at high pressures and temperatures

The manufacture of diamond drill bits (diameter up to 212 mm) at pressures up to 1.5 GPa and temperatures up to 1250°C is described. This technology includes sintering by electric heating within a thermally and electrically insulating shell in a steel high-pressure chamber, for 120 min. Such high-pressure sintering is found to be a relatively rapid process, and the equipment may be employed repeatedly. Steel highpressure chambers of cylinder–piston type with working diameters up to 280 mm are developed and produced. In bit manufacture by this means, matrix material with diamonds may be pressed onto steel housing; alternatively, it is possible to use a powder housing with diamonds or with holes for subsequent attachment of diamonds by soldering or mechanical methods. Bits with model cutting elements made of polycrystalline carbonado diamonds are manufactured, and their operational properties are verified. In drilling a marble block under loads up to 50 kN, at speeds of 355 rpm, mechanical speeds up to 20 m/h are attained. In the technology developed, the cutting properties of carbonado diamonds may be retained, but the thermal stability matches that of PCD diamond–hard-alloy composites. The bits are rugged enough for use in the most challenging drilling conditions. The metal–ceramic matrix permits the reliable attachment of cutting elements made of ASPK diamond composites. It is strong and wear-resistant. This is an energy-saving technology with little environmental impact and is fast. It may be used to produce wear- and corrosion-resistant metal–ceramic housings, with subsequent attachment of diamonds by soldering or mechanical methods, on the basis of PCD composites with varying thermal stability.     

Structure and properties of WC-Co alloys in solid-phase sintering. II. Mechanical properties of samples

The mechanical properties of hard WC-Co alloys produced by solid-phase sintering at various temperatures are discussed. It is shown that the bending strength and hardness of these alloys may be the same as those achieved in liquid-phase sintering. The difference between solid-phase and liquid-phase sintering is only in the time it takes to achieve the dense state. Excellent mechanical properties at rather low temperatures (1150–1200 °C) can be obtained by sintering under pressure. High hardness can be achieved at 1000–1100 °C by hot isostatic pressing of nanoscale powders. The excellent mechanical properties of solid-phase-sintered hard WC-Co alloys indicate that strong interphase and intercarbide boundaries occur earlier than the liquid phase.     

Mechanical and Thermal Properties of Pulsed Electric Current Sintered (PECS) Cu-Diamond Compacts

In this work, dispersion strengthening of copper by diamonds is explored. In particular, the influence of 50- and 250-nm diamonds at contents of 3 and 6 vol. pct on the mechanical and thermal properties of pulsed electric current sintered (PECS) Cu composites is studied. The composite powders were prepared by mechanical alloying in argon atmosphere using a high-energy vibratory ball mill. The PECS compacts prepared had high density (>97 pct of T.D.) with quite evenly distributed diamonds. The effectiveness of dispersoids in increasing the microhardness was more pronounced at a smaller particle size and larger volume fraction, explained by Hall–Petch and Orowan strengthening models. The microhardness of Cu with 6 and 3 vol. pct nanodiamonds and pure sm-Cu (submicron-sized Cu) was 1.77, 1.46, and 1.02 GPa, respectively. In annealing experiments at 623 K to 873 K (350 °C to 600 °C), the composites with 6 vol. pct dispersoids retained their hardness better than those with less dispersoids or sm-Cu. The coefficient of thermal expansion was lowered when diamonds were added, being the lowest at about 14 × 10^?6 K^?1 between 473 K and 573 K (200 °C and 300 °C). Good bonding between the copper and diamond was qualitatively demonstrated by nanoindentation. In conclusion, high-quality Cu-diamond composites can be produced by PECS with improved strength and better thermal stability than for sm-Cu.     

Composition dependence of mechanical properties of diamond segments

This research is devoted to studying the mechanical characteristics of diamond-drilling-tool matrix. The infiltration method at a temperature of 1100–1150°C for 15 min in hydrogen medium was used for making model diamond-containing and diamond-free samples of 24 × 7 × 8 mm matrices of two types differing in content of nickel and fused tungsten carbide, namely WC-Co-Cu (1) and WC-Co-Cu-Ni + cast tungsten carbide (2). A8K160 (500/400 μm), AC50 (500/400 μm), and SDB1125 (30/40 mesh, i.e., 600/425 μm) diamonds were used as diamond-filling materials with a concentration of 9 vol % in the matrix. The bending strength, hardness, density, porosity, and abrasive resistance of drilling tool matrix samples are measured. It is found that WC-Co-Cu-Ni matrix samples have higher hardness and abrasive resistance when compared with WC-Co-Cu, which is explained by the occurrence of nickel and solid particles of tungsten carbide solids in them. The introduction of diamonds in the matrices results in a substantial increase in their hardness (by 8–10 HRC units), which distorts the hardness measured data of matrices in the diamond layer of drill crowns.     

Ultrafine high-cobalt hard alloys. II. Connection between mechanical properties and structure

The experimental dependences of strength, plastic properties, hardness, and fracture toughness on sintering or pressing temperature for ultrafine alloy WC-41 wt.% Co are presented. The alloy densifies in solid phase and temperature varies from 950 to 1250°C. The dependences of mechanical properties are extreme, excepting fracture toughness. The properties reach their maximum values at 1050 to 1150°C depending on the type of testing. Fracture toughness continuously increases with densification temperature. The highest values of some properties are reached after additional solid-phase annealing. The mechanical properties of ultrafine high-cobalt alloy samples are assessed with the use of structural parameters and empirical equations established for standard hard WC-Co alloys sintered in liquid phase. The calculated and experimental values of properties differ: transverse rupture strength, fracture toughness, and yield strength show higher values, while hardness and compressive strength have lower values as compared with calculated ones.     

Interfacial segregation of Ti in the brazing of diamond grits onto a steel substrate using a Cu-Sn-Ti brazing alloy

Diamond grits were brazed onto a steel substrate using a prealloyed Cu-10Sn-15Ti (wt pct) brazing alloy at 925 °C and 1050 °C. Due to the relatively high concentration of Ti in the brazing alloy, the braze matrix exhibited a composite structure, composed of β-(Cu,Sn), a Cu-based solid solution, and various intermetallic compounds with different morphologies. The reaction of Ti with diamond yielded a continuous TiC layer on the surfaces of the diamond grits. On top of the TiC growth front, an intermetallic compound, composed of Sn and Ti, nucleated and grew into a randomly interwoven fine lacey structure. An interfacial structure developed as the interwoven fine lacey phase was semicoherently bonded to the TiC layer, with the Cu-based braze matrix filling its interstices. The thickness of such a composite layer was increased linearly with the square root of isothermal holding time at 925 °C, complying with the law of a diffusion-controlled process. However, at 1050 °C, the segregation behavior of Ti and Sn to the interfaces between the TiC layer and the braze matrix diminished, due to the increased solubility of Ti in the Cu-based liquid phase. The enhanced dissolution of Ti in the Cu-based liquid phase at 1050 °C also caused the precipitation of rod-like CuTi with an average diameter of about 0.2 μm during cooling. SnTi₃ was the predominant intermetallic compound and existed in three different forms in the braze matrix. It existed as interconnected grains of large size which either floated to the surface of the braze matrix or grew into faceted grains. It also exhibited a nail-like structure with a mean diameter of about 1 μm for the rod section and a lamellar structure arising from a eutectic reaction during cooling.     

Theory and technology of sintering, thermal and chemicothermal treatment

The studies on the densification of WC-Co alloys in solid-phase sintering are analyzed. It is shown that solid-phase sintering of alloys with tungsten carbide particles smaller than 2.0 µm is characterized by high densification (shrinkage) and results in compact samples in some cases. Shrinkage is established to be nonmonotonic over a wide range of sintering temperatures. There are at least three different stages of densification over the range from room to solidus temperatures. Approximate temperature ranges for densification stages are 100 to 1050 °C, 1050 to 1200 °C, and 1200 °C to the eutectic melting temperature. The stages mainly differ in the extent and rate of shrinkage and in the activation energy. The compaction stages are separated by characteristic temperatures. The most important is 1200 °C, which separates the second and the third stages. The maximum rate of shrinkage is observed mostly at this temperature. The variation of initial WC particles from 5 to 2000 nm does not significantly affect the temperature at which the solid-phase shrinkage rate is maximum. In most cases, there are two maximum rates of shrinkage in WC-Co sintering: one at 1200 ± 30 °C and the other at the solidus temperature.     

Influence of quenching methods on martensitic transformation and mechanical properties of P/M processed Cu–Al–Ni–Ti shape memory alloys

The effect of quenching conditions on phase transformation characteristics and microstructural features of Cu–Al–Ni–Ti shape memory alloys (SMAs) have been studied. The alloys were synthesised via conventional powder metallurgy process using elemental metal powders. Four different quenching techniques, such as (a) two-step quenching, first to 100°C and then to 0°C; (b) two-step quenching, initially to 40°C and later to 0°C; (c) direct quenching to 40°C and (d) direct quenching to 0°C, were used. The microstructural features and phase transformations that the alloys had undergone were studied using FE-SEM and XRD techniques. The martensitic phase transformation analyses were carried out by differential scanning calorimeter while the mechanical properties were studied by microhardness and flexural bending tests. The results obtained clearly indicate that the quenching routes followed have a remarkable influence on the properties of Cu-based SMAs.     

Development of High-Strength High-Temperature Cast Al-Ni-Cr Alloys Through Evolution of a Novel Composite Eutectic Structure

Aiming to develop high-strength Al-based alloys with high material index (strength/density) for structural application, this article reports a new class of multiphase Al alloys in the Al-Ni-Cr system that possess impressive room temperature and elevated temperature (≥ 200 °C) mechanical properties. The ternary eutectic and near eutectic alloys display a complex microstructure containing intermetallic phases displaying hierarchically arranged plate and rod morphologies that exhibit extraordinary mechanical properties. The yield strengths achieved at room temperatures are in excess of 350 MPa with compressive plastic strains of more than 30 pct (without fracturing) for these alloys. The stability of the complex microstructure also leads to a yield stress of 191 ± 8 to 232 ± 5 MPa at 250 °C. It is argued that the alloys derive their high strength and impressive plasticity through synergic effects of refined nanoeutectics of two different morphologies forming a core shell type of architecture.     

Diamond cutting tools with a Ni<Subscript>3</Subscript>Al matrix processed by reaction pseudo-hipping

Nickel aluminide, Ni₃Al, has high hot strength, which could help overcome the high heat and the interrupted vibrations that diamond cutting tools encounter during operation. Reaction pseudo-hipping, on the other hand, require only a short dwell time at high temperatures, which are detrimental to the diamond grits. Thus, it is promising to combine the unique nickel aluminide with the unique reaction pseudo-hipping process and replace the commonly used cobalt matrix. This study reports for the first time the process and application of reaction-pseudo-hipped Ni₃Al matrix for diamond tools. In this work, mixtures of elemental nickel, aluminum, boron powder, and diamond particles are reaction-pseudo-hipped. Densities greater than 99 pct and mechanical properties comparable to those of the cobalt are attained. With high-grade diamond grits, the tools thus prepared show, under dry cutting conditions, a grinding ratio 118 pct higher than that with the cobalt matrix.     

Mechanical Properties of Mg-Gd and Mg-Y Solid Solutions

The mechanical properties of Mg-Gd and Mg-Y solid solutions have been studied under uniaxial tension and compression between 4 K and 298 K (?269 °C and 25 °C). The results reveal that Mg-Gd alloys exhibit higher strength and ductility under tension and compression attributed to the more effective solid solution strengthening and grain-boundary strengthening effects. Profuse twinning has been observed under compression, resulting in a material texture with strong dominance of basal component parallel to compression axis. Under tension, twining is less active and the texture evolution is controlled mostly by slip. The alloys exhibit pronounced yield stress asymmetry and significantly different work-hardening behavior under tension and compression. Increasing of Gd and/or Y concentration leads to the reduction of the tension–compression asymmetry due to the weakening of the recrystallization texture and more balanced twinning and slip activity during plastic deformation. The results suggest that under compression of Mg-Y alloys slip is more active than twinning in comparison to Mg-Gd alloys.     

Powder Metallurgy Group Meeting,Coventry, 24–26 October 1977: Report of Proceedings

Abstract

The feasibility of producing room temperature superplastic Zn–Al alloys by hot extrusion of gas atomised powders has been investigated. Commercially pure zinc, and Zn–8wt-%Al and Zn–28wt-%Al binary alloys were gas atomised; the resulting powders were cold compacted into cylindrical billets and extruded to form consolidated rod. Two extrusion temperatures (200 and 300°C) were used, chosen to lie on either side of the invariant (eutectoid) temperature of 275°C. It has long been established that in conventional cast alloys rapid quenching from above this temperature is required to produce a microstructure having superplastic properties. (It was anticipated that the 300°C extrusions would contain quantities of near equilibrium eutectoid and thus be unlikely to deform superplastically. The 200°C extrusions were expected to exhibit a non-equilibrium structure that might have potential in terms of superplastic deformation.) The microstructures of the extrudates were investigated by transmission electron microscopy and the mechanical properties established by room temperature tensile testing and Charpy impact testing. PM/0502     

Ultrafine high-cobalt VK40 hard alloy. I. Structure and properties

Ultrafine WC-41 wt.% Co powders (VK40) are densified under 1000–1200 MPa at 950–1250 °C and in 0.13 Pa vacuum. It is examined how the pressing temperature and annealing at 1190 °C influence the density, structure, physical and mechanical properties of VK40 alloy. It is shown that high-pressure sintering produces dense samples with ultrafine structure (L_WC = 0.35–0.45 µm) and low degree of contact for carbide particles (contiguity C_WC = 0.08–0.1) in solid phase. The highest mechanical properties are exhibited by samples densified at 1150–1250 °C or by samples annealed after preliminary pressing at 1050–1150 °C. The alloy has the following properties: transverse rupture strength (TRS) of 3200–3400 MPa, fracture toughness of 25–33 MPa · m^1/2, Vickers hardness of 7.5–7.7 GPa under 300 N, compressive strength of 2600–2800 MPa, compressive offset yield stress σ_0.2 = 2200–2400 MPa, compressive plastic strain of 6.5–7.0%, and fracture energy of 180–200 MJ/m³. These mechanical properties of ultrafine VK40 alloy differ from those of standard impact-resistant coarse-grained hard metals in higher TRS, fracture toughness, and yield stress.     

Consolidation of diamond tools using Cu–Co–Fe based alloys as metallic binders

Abstract

The present work reports the results obtained on the evaluation of both the response of commercially available Cu–Fe–Co pre-alloyed powders during processing for the consolidation of diamond tools under several fabrication routes, and the performance of the tools during in field cutting operations. The new metallic binders look attractive since they combine good sinterability with adequate values of hardness and wear resistance, as observed from the cutting tests carried out on granite and marble. The consolidation routes under research were conventional hot pressing, pressureless sintering, and hipping after sintering. The amount of copper contained in these alloys leads to fully dense parts by hot pressing at temperatures approximately 150°C lower than those used for cobalt. Pressureless sintering experiments showed that full densification requires the application of hipping post-sintering treatments. During processing under non-reducing atmospheres, the presence of metallic oxides contained in the powder was observed to exert a direct influence on the degradation of the diamond grits.     

Examination of the Influence of Heat Treatment on the Properties of AI‐Si Alloys

In this paper the influence of heat treatment on the structural and mechanical properties of Al‐Si alloys was investigated. Silicon content in the examined alloys was in the range 11 to 14%, the contents of the other alloying elements were in the standard range [1] but all alloys were modified with strontium. The regime of the applied heat treatment was quenching (520°C/6h – cooling in water) + aging (205°C/7h –air cooling). The examinations were carried out at room temperature as well as at 250°C and 300°C. The obtained results showed a positive influence of the applied heat treatment on the mechanical properties of the examined alloys. The improvement of the mechanical properties can be considered as a consequence of a redistribution and change of morphology of the phases present in the structure of the alloys.     

Mechanical properties of NiAl-Y2O3-based powdered alloys produced by directional recrystallization

The mechanical properties of NiAl-Y₂O₃-based powdered composite alloys (0.5–7.5 vol %), including those with an NiAl intermetallic matrix alloyed with 0.5 wt % Fe and 0.1 wt % La have been studied. Structures with various aspect ratios (AR, the ratio of the grain length to the grain diameter) are formed using deformation and subsequent annealing. A combination of the optimum amount of strengthening phase (2.5 vol % Y₂O₃) and a quasi-single-crystalline structure with a sharp axial texture with the (100) main orientation and AR ≈ 20–40 provides the maximum short-term strength and life at temperatures up to 1400–1500°C. An NiAl-Y₂O₃ alloy (2.5 vol %) has the best strength properties among all known nickel superalloys at temperatures higher than 1200°C and can operate under moderate loads at temperatures higher than the working temperatures of nickel superalloys (by 100–400°C) and their melting points. Additional alloying with 10 wt % Co and 2 wt % Nb makes it possible to increase the ultimate tensile strength of an intermetallic NiAl matrix at 1100°C by a factor of 1.3–1.4.     

Fast aging kinetics of the AA6016 Al-Mg-Si alloy and the application in forming process

Preaging treatment of AA6000 alloys has been a focus of alloy development for automotive applications. A much better bake-hardening response can be achieved with preaged materials compared to those in the naturally aged state. Recently, fast aging kinetics have been found in preaged AA6016 alloys. A heat treatment at 230 °C to 260 °C for over 60 seconds can increase the strength of the material, in particular, the yield strength, significantly. Observations of high-resolution transmission electron microscopy (HRTEM) indicate that relatively large clusters exist in the preaged state; they can grow rapidly into needle-shaped semicoherent precipitates at 230 °C for over 60 seconds, leading to the rapid changes in the mechanical properties. During heat treatment at higher temperatures, the preaged material behaved in a similar manner as the naturally aged material. The fast aging kinetics have been applied in making thermal-treated blanks with microstructural gradients. The blanks were treated locally at 230 °C for approximately 90 seconds to increase the strength of the local region. A heat treatment at temperatures higher than 350 °C for approximately 10 seconds can effectively reduce the strength. A combination of these two treatments applied to different locations of a blank, introducing strong gradients in the mechanical properties, can improve the forming performance of the material significantly, relative to the homogeneous blanks in the original condition.     

Al-Fe-Ce alloys based on water-atomized powders for high-temperature applications

The microstructure and mechanical properties of Al-Fe-Ce alloys based on water-atomized powders between 20 and 300 °C are examined in comparison with the properties of similar alloys produced by other rapid crystallization techniques. Changes in atomization parameters vary both the cooling rate (from 10⁴ to 10⁶ K/sec) and powder size distribution (from 5 to 100 µm). The excellent compactability of water-atomized powders facilitates powder consolidation, which is based on hot extrusion and cold pressing of degassed powders. The mechanical properties are examined by tensile tests. The ultimate tensile strength is 500 to 550 MPa at 20 °C and 270 to 300 MPa at 300 °C at adequate plasticity. The properties achieved are comparable with those of similar alloys known from the literature.     

Processing Parameter Control of Lifetime-Limiting Failure Mechanisms in Al-Si Cast Alloys at Room and Elevated Temperatures

Aluminum-silicon cast alloys widely used throughout the transportation sector, A356, 319, and A390, have been studied with respect to chemical compositions and processing parameters that control the resultant mechanical behavior. First, the development of strengthening mechanisms is discussed in terms of the role that alloying elements, solidification behavior, and thermal treatments play. Based on this understanding, an extensive matrix of material conditions was developed and characterized in order to provide practical guidelines for alloy development. In order to provide an understanding of lifetime-limiting failure mechanisms, fatigue crack growth and hot compressive dwell behaviors were further investigated. Fatigue crack growth tests were conducted for all alloys at R?=?0.1 and room temperature, and creep–fatigue of 319 was studied at R?=???1.5 and 250 °C. The role of processing parameters in controlling the mechanical properties is identified and discussed, and recommendations for optimized design are made.     

Strength and ductile-phase toughening in the two-phase Nb/Nb5Si3 alloys

The effect of heat treatment on the mechanical properties of Nb-Nb₅-Si₃ two-phase alloys having compositions Nb-10 and 16 pct Si (compositions quoted in atomic percent) has been investigated. This includes an evaluation of the strength, ductility, and toughness of as-cast and hot-extruded product forms. The two phases are thermochemically stable up to ∼1670 °C, exhibit little coarsening up to 1500 °C, and are amenable to microstructural variations, which include changes in morphology and size. The measured mechanical properties and fractographic analysis indicate that in the extruded condition, the terminal Nb phase can provide significant toughening of the intermetallic Nb₅Si₃ matrix by plastic-stretching, interface-debonding, and crack-bridging mechanisms. It has been further shown that in these alloys, a high level of strength is retained up to 1400 °C.