Composite materials of diamond–(Co–Cu–Sn) system with improved mechanical characteristics. Part 2. The influence of CrB<Subscript>2</Subscript> additive on the structure and properties of diamond–(Co–Cu–Sn) composite

The structural alterations in the diamond–metallic binder transition zone in the diamond(78.4Co–11.76Cu–7.84Sn–2CrB₂) composite upon its sintering in a mold in hydrogen atmosphere at 800°C for 1 h have studied versus the hot re-pressing parameters, and the influence of such alterations on physical-mechanical and tribological properties of the composites has been clarified. Adding 2 wt % CrB₂ to the starting diamond?(80Co–12Cu–8Sn) composite is shown to raise the ultimate compression strength from 816 to 1720 MPa, bending strength from 790 to 1250 MPa, and wear resistance by a factor of 2.4. The improvement of properties of the composite and the increase of its wear resistance are provided due to the formation of Cr₃C₂ nanocarbide in the transition zone and the uniform distribution of Co, CrB₂ phases and CoSn inclusions in the volume of the metallic binder.     

Composite materials of diamond−(Co–Cu–Sn) system with improved mechanical characteristics. Part 1. The influence of hot re-pressing on the structure and properties of diamond−(Co–Cu–Sn) composite

We have studied the structure and tribological behavior of composite materials of the diamond–(Co–Cu–Sn) system, which were produced by sintering in molds at 800°C for 1 hour with subsequent hot re-pressing. It is shown that a change of hot re-pressing conditions makes it possible to produce nanocarbide Co₃C in the diamond–metal binder transition zone, instead of particles of structurally free graphite arising during graphitization of the diamond grain surface. The presence of nanocarbide provides an essential improvement of wear resistance of the composites.     

Fabrication and Wear Performance of (Cu–Sn) Solution/TiC<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Bonded Diamond Composites

The Cu(Sn)–TiC_x bonded diamond composites were prepared by in situ reaction sintering of Cu, Ti₂SnC and diamond powders. Effect of Ti₂SnC content on the phase composition, microstructure and grinding properties were studied. The result shows that Ti₂SnC was decomposed to TiC_x and Sn. And then, Sn atom dissolved into the crystal lattice of Cu and formed Cu(Sn) solution. The rich C formed at the interface between diamond and the matrix. Excess Ti₂SnC inhibited the formation of Cu solid solution and reacted with Cu to form Cu₃Sn. Additionally, its matrix was mainly composed of TiC_x with better wear resistance, which may improve obviously the grinding performance of the composites. The grinding ratio value of copper–diamond composite was only 132. The grinding ratio value of the composite contained higher Ti₂SnC content in the raw materials was 636.     

Shrinkage and shrinkage rate behavior in Cdiamond-Fe-Cu-Ni-Sn-CrB2 system during hot pressing of pressureless-sintered compacts

The paper addresses the effect of pressure and a chromium diboride additive on shrinkage and shrinkage rate in hot pressing and on mechanical properties of the resulting diamond-containing composites based on Fe, Cu, Ni, and Sn powders. The shrinkage rate curves are found to have a stepwise trend. The shrinkage rate variations are shown to be associated with the phase and structural changes that occur in this system. The authors have determined the initial composition and p,T-conditions that ensure process activation and simultaneous improvement in mechanical properties of the composite.     

ISM High-Performance Tools for Drilling of Oil and Gas Wells. Review

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.     

New method for preparing composite containing nanometre diamond particles

Abstract

Different powder mixing methods were used to prepare Al-5Cu and Cu-10Sn wt- based composites containing nanometre diamond. A new method for obtaining ultrafine Cu, Sn particles and a good distribution of nanometre diamond aggregates was developed. The nanometre diamond aggregates were well dispersed in the Cu-10Sn matrix. However, the distribution of nanometre diamond in the Al-5Cu based composite was unacceptable. Owing to the dispersion of nanometre diamond, Cu-10Sn based composite possessed higher hardness and lower bend strength than Cu-10Sn alloy.     

The effect of technological parameters of intensive electric sintering on the efficiency of inserts produced from diamond-containing composite materials in a cobalt binder

A device and express methods to analyze operating characteristics of diamond-containing composite materials in a cobalt binder have been developed. The experimental studies of the dependence of the diamond-containing composite material tools efficiency on intensive electric sintering have been conducted under the close-to-real operation conditions. Correlation dependences between technological parameters of sintering, microstructure, physico-mechanical properties, and operating characteristics of diamond-containing composite tool materials have been established. The ranges of variations and combinations of technological parameters of sintering, which are most promising in terms of the quality of the resultant materials, have been defined. On the strength of the data obtained an improved technology has been developed of producing segments from diamond-containing composite materials to equip tools with improved operating characteristics to be used in stone working.     

Polymer-diamond composites based on detonation nanodiamonds. Part 2

The paper shows the influence of diamond-containing mixture and detonation nanodiamonds on the physical-mechanical properties of polymer composites based on polyisoprene, butadiene-styrene, and polysiloxane rubbers. Adding a diamond-containing mixture is demonstrated to endow the composites with high strength and fatigue endurance indices. The cohesive strength is improved by a factor of 1.3–2.0 and the tearing strength is almost doubled. The use of composite nanodispersed fillers with a diamond-containing mixture in polysiloxane results in almost 1.7 times higher strength parameters.     

Influence of interfacial carbide layer characteristics on thermal properties of copper–diamond composites

Copper–diamond composites are increasingly being considered for thermal management applications because of their attractive combination of properties, such as high thermal conductivity (λ) and low coefficient of thermal expansion (CTE). In this research, thermal properties of Cu–diamond composites with two different types of interfacial carbides (Cr₃C₂ and SiC) were studied. The interface thermal conductance (h _c) was calculated with Maxwell mean-field and differential effective medium schemes, wherein experimentally measured λ was entered as an input parameter. The λ and h _c of both the Cu–Cr₃C₂–diamond and Cu–SiC–diamond composites are higher than those reported in previous studies for Cu–diamond composites with no interfacial carbides. The value of h _c is intimately related to the morphology and thickness of the interface carbide layer, with the highest h _c being associated with a thin and continuous interface carbide layer. A lower h _c resulting from a thicker Cr₃C₂ layer can provide an alternate explanation for a previously reported trend in λ of Cu–Cr₃C₂–diamond composites with different Cr-contents. The experimentally measured CTE was compared with the Turner and Kerner model predictions. The CTE of both the Cu–Cr₃C₂–diamond and Cu–SiC–diamond composites is lower and better matches the model predictions than the previously reported CTE of Cu–diamond composite with no interfacial carbides. The CTE of Cu–Cr₃C₂–diamond composites agrees better with the Kerner model than the Turner model, which suggests that deformation during temperature excursions involves shear.     

Wear and mechanical properties of carbon fiber reinforced copper alloy composites

The mechanical properties and wear behavior of lead-free metal matrix composite, and carbon fiber reinforced copper alloy composites were studied, and compared with a common leaded copper (Cu-6wt.%Zn-6wt.%Sn-3 wt.%Pb) alloy. The effects of carbon fibers and alloy element Sn on these properties were investigated. Carbon fiber/Cu–Sn–Zn composites showed higher hardness and bending strength than the leaded copper alloy when carbon fibers content is less than 12 vol.%. Tribological tests were conducted with disks made from these materials, and tested against a steel counterface. The carbon fiber/Cu–Sn–Zn composites showed higher wear resistance than the leaded copper alloy under a constant load of 50 N. Observations on surface morphology were utilized in understanding the wear properties of these materials. The results show that the wear mechanism of the leaded copper alloy is adhesive wear, while it is mainly adhesive wear accompanied by oxidative wear for the 12 vol.% carbon fiber/Cu–Sn–Zn composites. The 12 vol.% carbon fiber/Cu–Sn–Zn composites are likely to provide optimum substitutes for the leaded copper alloy under the load of 50 N.     

Effect of copper content on the thermal conductivity and thermal expansion of Al–Cu/diamond composites

Al–Cu matrix composites reinforced with diamond particles (Al–Cu/diamond composites) have been produced by a squeeze casting method. Cu content added to Al matrix was varied from 0 to 3.0 wt.% to detect the effect on thermal conductivity and thermal expansion behavior of the resultant Al–Cu/diamond composites. The measured thermal conductivity for the Al–Cu/diamond composites increased from 210 to 330 W/m/K with increasing Cu content from 0 to 3.0 wt.%. Accordingly, the coefficient of thermal expansion (CTE) was tailored from 13 × 10⁻⁶ to 6 × 10⁻⁶/K, which is compatible with the CTE of semiconductors in electronic packaging applications. The enhanced thermal conductivity and reduced coefficient of thermal expansion were ascribed to strong interface bonding in the Al–Cu/diamond composites. Cu addition has lowered the melting point and resulted in the formation of Al₂Cu phase in Al matrix. This is the underlying mechanism responsible for the strengthening of Al–Cu/diamond interface. The results show that Cu alloying is an effective approach to promoting interface bonding between Al and diamond.     

超高分子量聚乙烯/金属复合材料的摩擦磨损性能

用MM-200型摩擦磨损试验机研究了Ag、Cu、Co、Cr、Fe、Mo、W、Ni、Zn、Pb、Sn、Al等金属粉末填充超高分子量聚乙烯(UHMWPE)复合材料的摩擦磨损性能,利用扫描电子显微镜观察了复合材料磨损表面形貌.结果表明:在低速条件下,金属填料可降低UHMWPE复合材料的摩擦系数;在高速条件下,金属填料对UHMWPE复合材料的摩擦系数影响不尽相同.Ag、Cu、Co、Cr、Fe、Mo、W、Ni、Zn、Pb等金属填料可使UHMWPE的耐磨性显著提高, 而Sn、Al导致UHMWPE的磨损率增大;Ag的减摩抗磨效果最佳.     

Densification of hot-pressed composite materials for diamond tools

A set of compaction equations suitable for final stage of hot-press forming and sintering is deduced, all physical parameters are analyzed, the analysis results are consistent with a part of empirical formulas. Composites for diamond tools are taken as the subject of the investigation. Under the conditions of hot-forming sintering, the priority is given to the research of the relation between heat capacity C _p at constant pressure. By combining analysis of the set of compaction equations, we performed differential thermal analysis (DTA) in the differential scanning calorimetry (DSC) mode of heat capacity at constant pressure of pure Co powder, composite powder that consists of 663Cu and 35% Fe-based powder, analyzed the relationship between C _p and composite densification, and modified C _p of matrix composites containing 35% Fe-based composite powder for diamond tools in the mode of mixing a rare earth to make it as similar to C _p of pure Co as possible. Such modified powder is used in practical hot pressing of diamond tool composites and guides it with a set of compaction dynamical equations to radically improve the stability of practical performance (bending strength, hardness, impact ductility, porosity) of powder metallurgy composites and compaction of diamond tool composites.     

石墨镀Sn调控对石墨/Cu复合材料组织及力学性能的影响

石墨/Cu自润滑复合材料具有良好的摩擦学性能和耐腐蚀性能,在高速铁路领域具有广阔的应用前景.传统石墨/Cu自润滑复合材料中由于石墨与基体不润湿,复合材料界面结合强度低,在材料承受载荷时容易造成石墨相的剥离、脱落,导致复合材料在高载荷服役条件下性能较差.采用化学镀覆工艺在石墨表面镀覆软金属Sn元素调控石墨/Cu复合材料界...     

Effect of Electrical Discharge Machining on strength and reliability of WC–30%Co composite

Tungsten carbide/Cobalt (WC–Co) composite is one of the important composite materials, which is used for manufacturing of cutting tools, dies and other special tools. It has very high hardness and excellent resistance to shock and wear. It is not possible to machine this material easily with conventional machining techniques. Due to the good electrical conductivity of WC–Co, it is usually machined by Electrical Discharge Machining (EDM). EDM process often results in the surface damage of bulk WC–Co, and the influence of the damage would affect the reliability. It is important to investigate the effect of electric discharge machining process on the properties of WC–Co cemented carbides before applying its engineering application. For these composites, maintenance of proper fracture strength is an important concern and is to be controlled. In this work, an attempt has been made to investigate the fracture strength and the reliability of EDMed WC–Co composite using the Weibull distribution analysis. The comparison of results between the machined composites and un-machined composites is carried out and presented in this study.     

Ein neues Werkstoffkonzept zur trockenen Bearbeitung mineralischer Materialien

A new material concept for machining of mineral materials For the machining of mineral materials like rock, concrete and asphalt ultra hard cutting‐tools such as diamond tools are used. During the use diamond tools are cooled with water to remove the heat and to prevent an early deterioration of the diamonds. Without water cooling the diamonds at the cutting edge as well as in lower levels are damaged. For ecological and economic reasons a dry machining of mineral materials is of great interest. The consumption of coolant and the pollution of occupied buildings by alkaline water would be decreased. But specific diamonds tools are necessary to realise a dry machining. The Institute of Materials Engineering pursues a novel material concept for diamond impregnated composites to protect diamonds in deeper layers. Materials with a very low thermal conductivity are inserted in the diamond‐composites to protect the diamonds against heat and to reduce the deterioration of diamonds in lower levels. Cobalt and bronze (CuSn 85/15) with particle sizes of 45–90 μm and < 40 μm, diamonds with particle sizes of 300–450 μm and alumina with particle sizes of 350–500 μm, 150–210 μm and < 70 μm were used. The diamond‐alumina‐composites were powder metallurgically produced and were examined by light‐ and electron microscopy and digital image analysis.     

Interfacial characterization and thermal conductivity of diamond/Cu composites prepared by two HPHT techniques

With the aim of obtaining materials with high-thermal conductivities (TCs) for heat sink applications, diamond/Cu composites were produced via two different high-pressure-high-temperature (HPHT) techniques: powder metallurgy method (HPHT–PM) and infiltration method (HPHT–IM). The interfacial characteristics of composite materials are compared with respect to the sintering process and their effect on thermal properties is addressed. The HPHT–IM process is clearly more favorable than that of HPHT–PM and the obtained composites exhibited TCs as high as 717 W/mK for the former, but also as low as 200 W/mK for the latter. The advanced thermal property of HPHT–IM composites is attributed to a well-bonded interface layer with gradual and continuous element transition probably due to amorphous carbon detected by Raman spectra. EDS analysis indicate selective interfacial bonding between diamond {100} faces and Cu. Diamond skeleton with connected particles have been observed in this case, also resulting in enhanced interfacial bonding and thermal properties. The HPHT–PM composites with isolated diamond particles feature visible macro interfacial debonding, leading to rather low TC less than that of pure Cu.     

高压熔渗金刚石/铜复合材料的低温导热特性

为研究高压熔渗金刚石/铜复合材料导热率在低温区的变化规律,采用高压熔渗（HRF）的方法分别制备了不同粒度（100 μm,250 μm,400 μm）的金刚石/铜复合材料,利用扫描量热法分析评价了高压熔渗法制备的不同粒度金刚石/铜复合材料的低温导热特性,采用扫描电子显微镜（SEM）分析其显微组织。研究结果表明：由于高压熔渗制备的金刚石/铜复合材料中的部分金刚石发生聚晶反应,导致金刚石颗粒间晶界传热的热阻远小于界面传热热阻;高压熔渗条件下,金刚石颗粒内部变形破碎导致缺陷增多,且100~150 K低温下以声子为主要热载子的传热对裂纹和间隙等缺陷敏感,导致在较低温区内金刚石/铜复合材料的导热率低于普通压力熔渗（PF）所制备的金刚石/铜复合材料的导热率。     

Abrasive wear of individual grits in diamond rollers and sticks and its relation to the overall tool wear in dressing operations

Abrasive wear of individual grits in diamond dressing tools during the dressing of abrasive wheels is studied. The wear rate is assessed analytically allowing for mechanical-statistical and temperature characteristics of the grit operation in dressing with rollers and sticks, as well as for the temperature-induced variations of the diamond hardness. A relationship is established between wear of individual grits and that of the diamond-containing layer as a whole.     

Magnetic and superconducting nanowires

This article is focused on the use of electrodeposition and of various nanoporous templates for the fabrication of metallic nanowires made from single metals (Ni, Co, Pb, Sn), alloys (NiFe, CoFe, CoPt), and multilayers (Co/Cu, NiFe/Cu). An overview is given of our recent studies performed on both magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also discussed.