Diamond Abrasives Research Articles

Investigation of material removal in vibration polishing of NiCo alloys with millimetre-sized tools

Safety-related plastic parts for the automotive industry require sophisticated, retroreflector mould inserts with a surface roughness in the near optical range (Sa ≈ 20 nm). Due to wear, only a limited number of plastic parts can be moulded and visual inspection and reconditioning of the structured mould insert by manual polishing is tedious and costly. Current work aims to establish an automated process chain as a remedy but due to the limited access to edges and corners, a vibrational motion with a frequency of 133 Hz is applied. This paper investigates the fundamental influence of polishing parameters in this process like polishing pad, grain size of diamond abrasives and polishing time on the material removal and the Archard wear coefficient, which then is applied to estimate the ratio of 2- and 3-body abrasion and compared to the actual surface topography. It was found that the material removal rate is not constant and decreases with longer polishing times. Generally, larger grain sizes and denser polishing pads with shorter fibres cause a higher material removal rate. For all investigated parameter combinations, a 2-body abrasion was present, which is proven by both Archard wear coefficient and surface topography images.

An experimental analysis of strontium titanate ceramic substrates polished by magnetorheological finishing with dynamic magnetic fields formed by rotating magnetic poles

Strontium titanate (SrTiO3, STO) ceramic substrate is an incipient ferroelectric material with a perovskite structure and which has a wide range of applications in the fields of microwave, millimetre wave, and optic fibre. This paper reports on a system of experiments carried out on STO substrates using a new magnetorheological (MR) finishing process where dynamic magnetic fields are formed by magnetic poles rotate. The results show that a circular ring shaped polishing belt with a stability evaluation zone appears on the surface after being polished by MR finishing with a single-point dynamic magnetic field. The dynamic magnetic fields are stronger when the revolutions of magnetic pole increase and eccentricity of pole enlarge, with the surface finish is smoother and more material is removed. The optimum machining times, machining gap, oscillation distance, eccentricity of pole, revolutions of the workpiece and magnetic pole are 60 min, 0.8 mm, 0 mm, 7 mm, and 350 r min−1 and 90 r min−1, respectively, and the best MR fluid consists of 6 wt% of diamond abrasives in W1 particle size and 18 wt% of carbonyl iron powder in W3.5 particle size. A surface roughness of Ra and a material removal rate of 8 nm and 0.154 μm min−1 can be obtained in these optimum process conditions. Finally, the polishing mechanism for dynamic magnetic fields and the mechanism for removing material from STO ceramic substrates are discussed in detail.

Przecinanie materiałów niemetalowych tarczą diamentową

The article presents a specificity of cutting with abrasive diamond blade saws. The types of blades considering construction are discussed. Also possibilities of the application of this method in relation to various, hard – machinable mostly nonmetallic materials are described. Paper presents advantages and limitations concerning different types of blades.

Three-dimensional Topography Simulation Research of Diamond-wire Sawing Based on Matlab

The influence law of the surface topography and roughness by processing parameters of diamond wire-saw slicing simulation is researched in this paper. At First, the wire saw slicing model is built. The position relation between the wire saw and the machining surface is definite in the model. The motion trajectory of the diamond abrasive on the wire saw is generated. Processing the motion trajectory of the diamond abrasives and the 3D topography of the slicing surface is generated. According to the 3D topography and the roughness formula, the surface roughness can be calculated. Finally, by changing machining parameters, such as wire saw linear velocity and workpiece feed velocity, the corresponding surface roughness will be obtained. Therefore, the influence law of wire saw linear velocity and workpiece feed velocity on the surface roughness is studied. The influence law provides a theoretical basis to improve the quality of wire saw slicing.

Обоснование механизма доминирующего государственного участия в освоении ресурсов высоколиквидных полезных ископаемых Арктики

For a scientific discussion the authors present proposals on the formation in Russia of a new form of effective mineral resource base development of the strategic solid mineral resources in the Arctic zone of Siberia and the Far East. The mechanism is based on the prevailing govenmental participation in projects of development and exploitation of highly liquid metals (rare earth elements, Tomtor ore cluster in Yakutia) and minerals (diamond abrasive materials, Rock Popigai meteorite crater deposit in Krasnoyarsk region) in the Siberian Arctic, carried out under conditions of high risk. Shown, that due to the unique parameters of both rare earth and diamond ores flow of hi-tech products and semi-products is formed. With the extension of the technological and value chain - delivery to the domestic and the global markets of highly liquid products (oxides of rare earth metals and high-purity metals, technical super abrasive diamond powders and products for the treatment of materials). Thus, a cluster for the production of final products based on rare-earth metals and super abrasive rough diamonds with high added value can be created. Milestones and additional exploration operations, preparations for the operation and development of deposits are carried out by the State Corporation for Mineral Resources with the joint participation, investment, technological cooperation of private companies and research organizations. The Corporation could be considered as a platform for international cooperation and foreign investment in technological chains of a presented mega-project of development of two closely located deposits. Introduced organizational and economic mechanism allows to: a) carry out public administration of complex resource projects in the Arctic and to develop them to an economically efficient level with a gradual sale of business projects to the private sector; b) to initiate and stimulate long-term scientific and technological development in conditions of high risk; c) to form a system of preferences for the development of Russian high-tech exports; d) ensure Russia’s economic presence and increased geopolitical and geo-economic interests in the Arctic.

Photocatalysis assisting the mechanical polishing of a single-crystal SiC wafer utilizing an anatase TiO2-coated diamond abrasive

This study introduces a new technique for depositing photocatalytic TiO2 thin layers on a nanodiamond (ND) abrasive to polish a single-crystal 6H-SiC wafer with sol-gel tools. A controllable and simple method is utilized to prepare ND/TiO2 composite abrasives by isothermal hydrolysis without conventional post-heating treatment for crystallization. The composites are characterized by X-ray diffraction and transmission electron microscopy. The TiO2 layer appears on the ND surface completely and continuously, and anatase TiO2 can be synthesized directly in this manner. An electrochemical experiment is performed to oxidize NaNO2 utilizing an ND/TiO2 electrode. Results indicate that ND/TiO2 with a hydrolysis reaction time of 18h exhibits the best oxidative activity. The generation of hydroxyl radical (OH) from the ND/TiO2 composite has increased upon exposure to UV irradiation. A comparative polishing experiment revealed that an ultra-smooth surface and a higher MRR were achieved when applying the ND/TiO2 composite abrasives, superior to those of pristine diamond abrasives. This scenario is due to the SiC being oxidized by ·OH and forming a relatively soft SiO2 layer.

Prediction of sawing force for single-crystal silicon carbide with fixed abrasive diamond wire saw

Fixed abrasive diamond wire saw has been used to cut hard-and-brittle materials into wafers, such as silicon carbide. The force of a single abrasive determines the cutting depth, and affects material removal mode and crack propagation length. Therefore, the sawing force is a key factor that affects the surface/subsurface quality of wafers. In this paper, a numerical sawing force predicting method considering wire saw parameters was proposed with the combination of both ductile removal and brittle fracture removal for each single abrasive. A new calculation method of single abrasive cutting force considering frictional force component and new material removal way considering the effect of lateral crack were adopted. Then the influences of process parameters and wire parameters on sawing force were analyzed. Finally, mathematical sawing force formulas described by both process parameters and wire saw parameters were obtained using the new sawing force prediction method. The validity of this prediction method and sawing force formulas was verified through experiments in the literature under the same process parameters and wire saw parameters.

Damage-free finishing of CVD-SiC by a combination of dry plasma etching and plasma-assisted polishing

To realize the damage-free finishing of CVD-SiC substrates, which are used as materials for space telescope mirrors and glass lens molds, plasma chemical vaporization machining (PCVM) and plasma-assisted polishing (PAP) were combined. In this study, the properties of such CVD-SiC substrates, including their surface morphology, composition and crystalline orientation, were investigated. Lapping using diamond abrasives and conventional chemical mechanical polishing (CMP) using CeO2 slurry were conducted for comparison with the proposed atmospheric-pressure-plasma-based finishing process. Many scratches and a subsurface damage (SSD) layer were formed by the diamond lapping of CVD-SiC. Conventional CMP using CeO2 slurry was conducted for the damage-free finishing of CVD-SiC. However, the polishing efficiency was very low. In the proposed process, PCVM, which is a noncontact dry etching process, was performed to remove the SSD layer while PAP, which combines plasma modification and soft abrasive polishing, was performed for damage-free surface finishing. PCVM was conducted on a diamond-lapped CVD-SiC surface. After PCVM for a short duration of 5min, the scratches and SSD layer formed by lapping were completely removed, although the surface roughness was slightly increased. PAP using a resin-bonded CeO2 grindstone was conducted to decrease the surface roughness of CVD-SiC processed by diamond lapping and PCVM for 5min, for which a loose-held-type grindstone was demonstrated to be very useful. A flat and scratch-free surface with an rms roughness of 0.6nm was obtained after PAP finishing.

Investigation on removal features of fixed abrasive diamond pellets based on elasticity tool

To obtain removal functions with high removal rate and stability in the polishing of hard and brittle material, an optical fabrication technology based on fixed abrasive diamond pellet (FADP) elasticity tool (ET) is designed. In this paper, we focus on the removal characteristics of ET, including removal profile, removal rate, stability of removal functions (RFs), and surface roughness. ET is analyzed theoretically about removal rate, stability, and fine surface adaptability. Modeling of the static influence function of ET based on finite element analysis (FEA) is proposed and fitted. A series of experiments are conducted to verify the effectiveness of the model. Within 640 min, the pellets could provide highly stable RFs with removal rate 1.71 mm3/min. In addition, the surface roughness about 43 nm is obtained.

Plastic deformation of the plastic matrix–hard inclusion composite system during high-temperature gas extrusion

The results of investigations of the production of abrasive rod or wire diamond tools by high-temperature gas extrusion are presented. The versions of preparation of an initial metallic workpiece filled with a mixture of abrasive diamond grains are considered. The forming of plastic materials with hard inclusions, which is caused by deformation redistribution in the volume and is accompanied by the formation of pores and discontinuities adjoined to the hard inclusions, is considered. The results obtained demonstrate the prospects of application of high-temperature gas extrusion for the production of diamond tools for various purposes.

Speed ratio optimization for ceramic lapping with fixed diamond pellets

High efficiency and stability are known as the advantages of fixed abrasive lapping for fabricating various materials, which are due to the effective positions of fixed abrasives on the tool surface and controllable trajectories during lapping. For speed ratio is regarded as one of the most important parameters in governing abrasive trajectory distribution, this work will focus on optimizing speed ratio of a fixed abrasive diamond pellet (FADP) pad for lapping alumina ceramic in order to reveal the influence of speed ratio on abrasive trajectory distribution and lapping results, which is of most importance to achieve a better surface workpiece. To obtain an optimal speed ratio in lapping, a method of extracting abrasive position information is put forward, and it is further used to optimize speed ratios based on trajectory analysis. Lapping experiments are carried out on alumina ceramics by a FADP pad, and removal characters of the FADP pad are investigated, including removal profile, surface morphology, trajectory scratches, surface roughness, and etc. Results show that the arranged structure of the FADP pad aggravates the influence of speed ratios on abrasive trajectory distribution. With the optimal speed ratios, better flatness and surface roughness of alumina ceramic can be achieved for the lower trajectory non-uniformity and a more complex trajectory distribution. The method of abrasive position information extraction and trajectory analysis can be used to optimize speed ratio for special lapping pads in different applications, especially for structured pad, which can further take advantage of fixed abrasive pads.

Polishing Characteristics of Transparent Polycrystalline Yttrium Aluminum Garnet Ceramics Using Magnetic Field-Assisted Finishing

Transparent polycrystalline yttrium aluminum garnet (YAG) ceramics have garnered an increased level of interest for high-power laser applications due to their ability to be manufactured in large sizes and to be doped in relatively substantial concentrations. However, surface characteristics have a direct effect on the lasing ability of these materials, and a lack of a fundamental understanding of the polishing mechanisms of these ceramics remains a challenge to their utilization. The aim of this paper is to study the polishing characteristics of YAG ceramics using magnetic field-assisted finishing (MAF). MAF is a useful process for studying the polishing characteristics of a material due to the extensive variability of, and fine control over, the polishing parameters. An experimental setup was developed for YAG ceramic workpieces, and using this equipment with diamond abrasives, the surfaces were polished to subnanometer scales. When polishing these subnanometer surfaces with 0–0.1 μm mean diameter diamond abrasive, the severity of the initial surface defects governed whether improvements to the surface would occur at these locations. Polishing subnanometer surfaces with colloidal silica abrasive caused a worsening of defects, resulting in increasing roughness. Colloidal silica causes uneven material removal between grains and an increase in material removal at grain boundaries causing the grain structure of the YAG ceramic workpiece to become pronounced. This effect also occurred with either abrasive when polishing with iron particles, used in MAF to press abrasives against a workpiece surface, that are smaller than the grain size of the YAG ceramic.

Analytical Force Modeling of Fixed Abrasive Diamond Wire Saw Machining With Application to SiC Monocrystal Wafer Processing

Free abrasive diamond wire saw machining is often used to cut hard and brittle materials, especially for wafers in the semiconductor and optoelectronics industries. Wire saws, both free and fixed abrasive, have excellent flexibility, as compared to inner circular saws, outer saws, and ribbon saws, as they produce a narrower kerf, lower cutting forces, and less material waste. However, fixed abrasive wire saw machining is being considered more and more due to its potential for increased productivity and the fact that it is more environmentally friendly as it does not use special coolants that must be carefully disposed. The cutting forces generated during the wire saw process strongly affect the quality of the produced parts. However, the relationship between these forces and the process parameters has only been explored qualitatively. Based on analyzing the forces generated from the chip formation and friction of a single abrasive, this study derives an analytical cutting force model for the wire saw machining process. The analytical model explains qualitative observations seen in the literature describing the relationship between the cutting forces and the wafer feed rate, wire velocity, and contact length between the wire and wafer. Extensive experimental work is conducted to validate the analytical force model. Silicon carbide (SiC) monocrystal, which is employed extensively in the fields of microelectronics and optoelectronics and is known to be particularly challenging to process due to its extremely high hardness and brittleness, is used as the material in these experimental studies. The results show that the analytical force model can predict the cutting forces when wire saw machining SiC monocrystal wafers with average errors between the experimental and predicted normal and tangential forces of 9.98% and 12.1%, respectively.

Mirror-Like Surface Finishing of PCD by Fixed Abrasive Polishing

Polycrystalline diamond (PCD) has excellent properties such as high hardness, high chemical inertness, high wear resistance and a low friction coefficient. Thus, it has been expected to be applied to used in various mechanical parts such as sliding parts. However, diamond is difficult to machine owing to its high hardness and chemical inertness. Therefore, a highly efficient and high-quality machining process is required for PCD. In this study, the authors developed fixed abrasive polishing tools for the mirror-like surface finishing of PCD that contain mechanochemical abrasive grains with diamond grains. As a result of fixed abrasive polishing experiments, it was clarified that a mirror-like surface can be obtained by fixed abrasive polishing using a tool containing SiO2 and diamond abrasives. Moreover, it was found that the removal efficiency can be increased under a high-temperature condition.

Study on the processing characteristics of SiC and sapphire substrates polished by semi-fixed and fixed abrasive tools

The semi-fixed and fixed polishing film with diamond and alumina abrasive are used for a contrastive experiment involving polishing SiC and sapphire substrates in this study. The material removal rate (MRR) and surface topography of substrate, the protrusion height of abrasive together with the wear debris, are investigated to reveal the processing characteristic of substrates. The removal mode of substrate is brittle removal when the material removal scale is tens of nanometers or more. It is plastic removal mode when the material removal scale is nanoscale. A smooth substrate surface with nanoscale roughness and a relatively high MRR can be achieved simultaneously only when the material removal scale is uniform with a size of tens of nanometers.

Możliwości zastosowania i analiza efektów przecinania wybranych materiałów metalicznych narzędziem strunowym

Możliwości zastosowania i analiza efektów przecinania wybranych materiałów metalicznych narzędziem strunowym

Adsorption and deposition of micro diamond particles in preparing diamond magnetic abrasives by electroless composite plating

Electroless composite plating is a valuable way to prepare diamond magnetic abrasives. Based on the two successive adsorption steps' principle, an adsorption model was established to demonstrate the relationship between the metallic matrix powders and micro diamond particles during the electroless composite plating. The concentration of micro diamond particles suspended in the plating solution, the diamond grit size, total surface area of the metallic matrix powders as well as the plating temperature, were taken into consideration for the adsorption of micro diamond particles. Diamond magnetic abrasives were prepared by the electroless composite plating method using iron particles and micro diamond particles. The experimental results show the adsorption rate of micro diamond particles on iron powder substrate can be forecasted by the established formula. The optimal ratio of micro diamond particles and Ni-P alloy in the deposit can be determined in preparing diamond magnetic abrasives by electroless composite plating.

Finite element analysis of multi-wire saw silicon rods with consolidated abrasive diamonds

A cutting model is presented in the paper for multi-wire saw silicon rods with consolidated abrasive diamonds. The stress of single diamond particles is analyzed. Besides, the calculation formula of normal and tangential cutting force is found out by formula derivation and calculation. The paper uses ANSYS 15.0 to make finite element analysis for multi-wire saw silicon rods with consolidated abrasive diamonds by loading different process parameters, including wire-line speed and feeding force. Meanwhile, according to removing mechanism of brittle materials, when the maximum cutting depth of single abrasive diamond silicon is less than the critical cutting thickness, the cutting way of multi-wire saw silicon rods is plastic removal. Comparing the deformation by finite element analysis with the maximum cutting depth, the error is not more than 15 %. So the cutting model and calculation of cutting force of multi-wire saw silicon rods with consolidated abrasive diamonds are proven to be basically consistent. The results indicate that when the wire-line speed is constant, with the increase of the feeding force, the maximum cutting depth is also increased, and with the feeding force is constant, with the increase of the wire-line speed, the maximum cutting depth increases first and then decreases. Therefore, considering the maximum cutting depth, setting the wire-line speed to 900 m/min and the feed force to 725 N is the best cutting process parameters.

Experiment study on electroplated diamond wire saw slicing single-crystal silicon

This paper conducted the slicing experiments of single-crystal silicon using a reciprocating electroplated diamond wire saw. The machined wafer topography and wire wear were observed by using scanning electron microscope (SEM). The influences of process parameters and cutting fluids on single-crystal silicon wafer surface roughness (SR), subsurface micro-crack damage (SSD) depth, total thickness variation (TTV) and warp were investigated. The bonded interface sectioning technique was used to examine the cut wafers SSD depth. Study results show that a higher wire speed and lower ingot feed speed can produce lower wafer SR and SSD; the lower warp of wafer needs lower wire speed and ingot feed speed; and low wafer TTV can be obtained by an appropriate matching relationship between wire speed and ingot feed speed. The synthetic cutting fluid has a better total effect to improve the wafer quality. The pulled-out of diamond abrasives is the main wear form of wire, which indicates that more research on improving the abrasives retaining strength on wire surface should be investigated in fixed-abrasive wire manufacturing process, in order to improve the wire life and wire saw machining process.

Study of surface finish of fiber-reinforced composite molds

One of the primary processes for the production of composite parts is the liquid composite molding process. This process is based on the injection of resin into a mold, which is usually metallic. Today, studies are being undertaken to produce these molds using Hextool™, a carbon fiber–reinforced thermosetting plastic. The molds, constructed by draping prepregs, must be finished by free-form machining to ensure the dimensional and surface quality requirements. An arithmetic roughness of 0.8 µm is required, and this quality is not attained by milling operations. Thus, a manual polishing operation is necessary. However, to minimize the time taken by this manual operation, it is necessary to verify the roughness obtained by milling. Thus, the work presented in this article consists first of a study of the capability of milling to produce molds from Hextool with given surface quality requirements. The conclusion of this study is to define values of radial depth of cut to attain a surface quality with minimum machining time. Second, this work highlights how to replace the manual polishing operation by a machining operation with an abrasive diamond tool. Thus, the capability of an abrasive diamond tool to machine a mold with high surface requirements is discussed.