Papers by Keyword: Polycrystalline Diamond (PCD)

Abstract: This paper deals with a new PCD named EC-PCD which is made up of boron doped diamond particles and its properties related to EDM machinability. For the purpose of improving various properties of standard PCD including resistance to heat, wear and reactivity, a new PCD (EC-PCD) was manufactured on a trial basis using electrically conductive diamond particle as a basic ingredient. Grain size, resistivity and thermal conductivity of the boron doped diamond used are 10μm, 5~37×10Ω•m and 440~580W/m•K. In this report, machinability of newly developed PCD (EC-PCD) by wire EDM was investigated in comparison with that of standard PCD. In wire cutting of 2 types of PCD in water under the condition of open gap voltage: ue=80V, set peak current: iP=0.8A and pulse condition: te/to=20/20μs, it was found that roughness of the first cut surface of standard PCD was approximately 8μm Rz, while that of EC-PCD was far better such as 3μm. Also in finish cut (7th cut), the latter achieved the value of Rz=1.7μm while the former achieved only the value of Rz=2.7μm. Expecting better performance, EC-PCD was tested also in oil. As a result, the best achieved roughness was improved to Rz=0.4μm with no chipping on the edge. To explore a reason for such a good roughness obtained, the cut samples were observed on the SEM, which revealed that the diamond particles in EC-PCD were flattened by electro discharge.

Abstract: Industrial application of synthetic diamond ceramics is growing very fast due to their super hardness, superb wear resistance and long-life durability. In rock, concrete and metal cutting, drilling, mining and quarrying and dimension stone industries, cutting tools made of diamond composites or impregnated diamond composite segments are gradually replacing the more commonly used cemented tungsten carbide (WC) tools. Through its SMARTCUT research program, CSIRO in the past 15 years has developed harder and stronger thermally stable diamond composite (TSDC) drag picks to encourage and help manufacturing and mining industries improve their cutting performance by replacing these traditional WC cutting tools with the new revolutionary TSDC tools. This improvement process however is much more complex than a simple material or cutting tool replacement, since the mechanism and configuration of cutting are substantially different in the two cutter head systems and its successful implementation requires a better understanding of the basics of rock cutting. Some of the factors influencing the differences are: cutter wear, fracture toughness, compressive and tensile strength, thermal properties, geometrical shape, spacing, angle of attack, rake angle, sharpness and bluntness characteristics, lacing design and cutter arrangements. Besides, it is most important to understand the relation between the tool or tool force and the fragmentation of the rock, which is the main focus of this paper.

Abstract: This investigation aims to develop a quantitative model to estimate the material removal of polycrystalline diamond composites by dynamic friction polishing. The model accounts for not only the polishing parameters that govern the material removal mechanisms, but also the constitutive properties of the diamond composites subjected to polishing. The model prediction was justified by relevant experimental measurements.

Abstract: Sintered polycrystalline diamond (PCD) compacts are normally used for cutting tools, drill bits and wire dies. A novel application of PCD has been developed to use its entire surface carved to create different patterns which are triangle or square shape loaded with leveled millers that can shave brittle materials in ductile mode. Due to numerous cutting edges formed on the same level of PCD tools, which can be used to thin the wafer surface to achieve both flatness and smoothness of the industrial requirements. SEM has been used to observe the surface and subsurface of the thinned wafer surface. The critical depth of cut between ductile and brittle cutting mode is close to 2 µm in this thinning operation. The damaged layers of machined surface have been observed and studied in this paper.

Abstract: This article reviews the state-of-the-art techniques for polishing diamond and polycrystalline diamond composites. A focus is on their material removal mechanisms and features. It concludes that while each of them has its advantages and drawbacks, the technique by dynamic friction has a promising potential for polishing production.

Abstract: When cutting titanium alloy, the temperature of a cutting tool edge is easy to rise and the tool edge is tend to be worn away quickly because the titanium alloy has the characteristics of low thermal conductivity and high chemical activity. Therefore, it is difficult to achieve a balance between the productivity and the tool life in cutting the titanium alloy, namely, low-speed cutting must be carried out at present. To examine the possibility of the improvement in the cutting efficiency, a PCD (polycrystalline diamond) tool having high thermal conductivity was adopted to the cutting of titanium alloy and its cutting performance was investigated. The PCD tool was found to have excellent flank wear resistance compared with conventional cemented carbide tools. It was also revealed that unprecedented high speed cutting become possible by use of PCD tool with an application of high pressure coolant.

Abstract: This paper discusses the temperature characterization for nano-polishing of polycrystalline diamond composites (PCDCs) by combined experimental and theoretical modelling. It was found that a higher polishing pressure-speed combination results in a higher temperature rise and material removal rate. To optimize the nano-polishing of PCDCs and achieve a surface roughness of Ra = 50 nm, the interface temperature at polishing needs to be maintained at an appropriate level.

Abstract: Diamond is the hardest material and has high chemical resistant which is one form of carbon. In the present work a study was carried out on polycrystalline diamond coated Si3N4 substrate. The diamond was deposited by Microwave Plasma Assisted Chemical Vapor Deposition (MPACVD) under varying deposition parameters namely CH4 diluted in H2, microwave power and chamber pressure. SEM and AFM are used to investigate the surface morphology and surface roughness. Nucleation phenomena and crystal width were also studied using AFM. Based on SEM investigation it was found that the chamber pressure and %CH4 have more significant effects on nucleation and facet of polycrystalline diamond, In addition microwave power has an effect on the diamond facet that changed from cubic to cauliflower structure. Surface roughness results show that increasing the %CH4 has decreased surface roughness 334.83 to 269.99 nm at 1 to 3% CH4, respectively. Increasing microwave power leads to increase in diamond nucleation and coalescence which lead to less surface roughness. Increasing gas pressure may eliminate Si contamination however it reduces diamond nucleation.

Abstract: This paper presents a cost-effective technique for achieving optical surface finish of thermally stable polycrystalline diamond (PCD) composites using dynamic friction polishing (DFP). The effect of polishing parameters on the material removal rate and surface characteristics of polished specimens were studied. The surface characterisation was carried out by optical microscopy, atomic force microscopy (AFM), scanning electron microscope (SEM) and its attached energy dispersive X-ray (EDX) analysis. It was found that optical surface finish of PCD with roughness Ra = 50 nm could be obtained efficiently with nearly a ten fold reduction in polishing time compared to the currently used method in industry.

Abstract: This paper proposes a new PCD (polycrystalline diamond) wheel with porous skeleton structure realized by removing the cobalt binder from PCD by EDM (electrodischarge machining), and investigates the grinding characteristics of the wheel. The pores are made successfully on PCD by adopting appropriate EDM conditions. The efficiency of making the pores is found to be higher, when the size of the diamond grains in the PCD material is small, and jumping motion to the copper electrode is not given during the EDM. A porous PCD grinding wheel made by this method using a rotating circular PCD (grain size of 10'm) disc of 20mm diameter has a good skeleton structure with sufficient projections on the wheel surface. A satisfactory grinding characteristics with a surface finish of Ra=0.02'm in grinding on a tungsten carbide work is achieved.