Diamond Abrasives Research Articles

Influence of contact form on mechanical wear characteristics of single diamond scratching on Ta12W

Purpose Mechanical wear is the main wear form of abrasive single crystal diamond (SCD) grit. The mechanical wear of SCD grit has a significant influence on the tool life and machining quality. This paper aims to investigate the influence of grit–workpiece contact form on the mechanical wear characteristics of SCD grit. Design/methodology/approach Three different grit–workpiece contact forms, which involved point/line/face contact forms, are investigated to reveal the wear mechanism of SCD grit scratching on Ta12W. The wear morphology, wear volume and scratching forces are measured, and the stress models of different contact forms are analyzed. Findings The results show that mechanical wear mainly occurs in the grit–workpiece contact area and increases gradually from contact area to entire SCD grit. The scratching forces vary with the mechanical wear progress of SCD grits. The SCD grit with point contact form is the most prone to produce wear. The SCD grit with face contact form can remove more material volume than the other two SCD grits, and it is the most wear resistant. The stress state is closely related with the mechanical wear of SCD grit. The contact form has a significant influence on the mechanical wear of SCD grit. Originality/value The results of this study can provide a theoretical basis for the fabrication of abrasive tools.

Effect of diffusion barrier and interfacial strengthening on the interface behavior between high entropy alloy and diamond

The double effect of diffusion barrier and interfacial strengthening on the interface behavior in a Ti-coated diamond and high entropy alloy (HEA) composite was investigated. The first-principles simulations exhibited that the in-situ formed TiC played a significant role as a diffusion barrier between diamond and HEA matrix, resulting in the reduction of sp2 hybridization of diamond and enhanced the interface bonding strength. The simulation results were further confirmed by experiments. In Ti-coated diamond-HEA composite fabricated by selective laser melting, the TiC layer obstructed the direct contact between diamond particles and the transition metal elements in HEA, thus preventing graphitization of diamond and enhancing the interface bonding strength. Moreover, part of Ti in Ti coating entered into the HEA matrix and increased the lattice distortion, resulting in substitutional solution strengthening effect and improving the retention on diamond abrasives. The superior wear properties of Ti-coated diamond composite attributed to the diffusion barrier of TiC and interfacial strengthening of TiC and Ti containing HEA solid solution.

Characteristics of Diamond Abrasive Used in Magnetic Abrasive Finishing of Nickel-Based Superalloys

Abstract Nickel-based superalloys have a wide range of high-temperature applications such as turbine blades. The complex geometries of these applications and the specific properties of the materials raise difficulties in the surface finishing. Magnetic abrasive finishing (MAF) has proven effective in finishing the complex geometries. In MAF, the magnetic properties of the workpiece, tool, and abrasive play important roles in controlling finishing characteristics. This paper presents the effects of nickel coating on the abrasive behavior during finishing and resulting finishing characteristics of Ni-based superalloys. The Ni-coated diamond abrasive is more attracted to the magnet than the Ni-based superalloy surface. As a result, fewer Ni-coated diamond abrasive particles, which are stuck between the magnetic-particle brush and the target surface, participate in surface finishing. Because of this, coupled with the reduced sharpness of abrasive cutting edges due to the coating, Ni-coated diamond abrasive cannot effectively smooth the target surface in MAF. However, the Ni coating is worn off during finishing of the hard, rough, additively manufactured surface. Then, the diamond abrasive participates in finishing as uncoated diamond abrasive and facilitates the material removal, finishing the target surface.

An investigation on the dressing contact behavior between vitrified bonded CBN abrasive wheel and diamond grit dresser

Abstract In order to better understand the dressing behavior, an investigation was carried out to detect the contact zone between vitrified bonded cubic boron nitride (V-CBN) abrasive wheel and diamond grit dresser. The grinding experiment of single diamond grit dresser on V-CBN abrasive segment was designed and conducted to approach the actual dressing process. The moving trajectory during dressing was calculated and discussed. Acoustic emission (AE) signals were applied to evaluate the wear progression of V-CBN abrasive wheel. Results obtained discovered that the different trajectory length would result in different wear patterns of diamond grit dresser and vitrified bond of V-CBN abrasive wheel. With the increase of wear ratio, the AE root-mean-square (RMS) voltages also had an increasing trend during dressing V-CBN wheel. Furthermore, a shorter dressing trajectory length produced a lower and more stable surface roughness, a lower tool radial wear and a higher grinding ratio in the grinding experiment of Inconel 718 nickel-based superalloy.

Abrasive Segmentation of Multiple Diamond Images Based on Secondary Morphological Reconstruction

Faced with a lot of noise problems in diamond abrasive image segmentation under complex background, a segmentation method of diamond abrasive images is proposed based on secondary morphological reconstruction. The method of histogram equalization was firstly used to pre-process the original image, which aim is to improve the image by adjusting the global contrast, and an appropriate structural element is constructed to carry out to determine abrasive size by using the morphological smoothing operation; Secondly, the first morphological reconstruction is carried out to further virtualize the complex background and clear garget abrasives by using the geodesic corrosion operation; Then, the second morphological reconstruction is carried out by calculating geodesic expansion operation. Combined with the local extreme value processing of the image, each target abrasive area can be obtained. Finally, the segmented target abrasive area is used to extract the multiple abrasives from complex background. It is found that the complex background noise can be readily eliminated by the proposed method, and the abrasives in the image can be well segmented. The results show that segmentation boundary is clear, without background noise, and the segmentation region is significant. The extracted diamond abrasives can be used for advanced image analysis such as abrasive characteristics and abrasive identification.

Electrochemical cleaning grinding (ECCG) of aluminum alloy 6061 with electroconductive resin-bonded diamond wheels

A new manufacturing process named Electrochemical Cleaning Grinding (ECCG) is introduced to help reduce wheel loading in grinding of the highly ductile metals which exhibit high adhesion tendency. The key component of the ECCG system is an electroconductive resin-bonded diamond wheel, and its abrasive layer is made of phenolic resin bond and core-shell structured Ni-P alloy coated diamond abrasives. The alloy coating over diamond grains not only helps to increase the bond strength between the resin and the abrasives but improve the electrical conductivity properties of the grinding wheel. During the ECCG process, the abrasives on the wheel surface simultaneously act as micro cutting edges as well as microelectrodes where the anodic dissolution of the adherent metal materials takes place. This dissolution process is defined as “cleaning”. When the rate of accretion of adherent material is balanced by its electrochemical dissolution rate, the sharp abrasives are exposed to carry out efficient grinding, so that better grinding performance can be achieved. The grinding experiments of aluminum alloy 6061 (AA6061) were conducted to verify the effectiveness of the ECCG process. Compared with conventional grinding experiments, the most important changes brought in by the ECCG are the decrease in wheel loading degree and the improvement in machined surface quality. Additionally the electric energy consumption of the cleaning process is relative low and equal from 1.88 × 10−3 J/mm3 to 9.34 × 10-3 J/mm3.

Cost-Efficient High-Throughput Polishing of Silicon Carbide Seed Crystals

Polishing of Silicon Carbide (SiC) seed crystals and substrates to achieve an extremely smooth, level surface, and an optically clear finish takes many surface finishing steps with very long processing times producing a significant amount of slurry waste and utilizing numerous lapping and polishing machines. This paper presents a newly developed cost-efficient SiC polishing process which reduces these operations to two surface finishing steps for achieving an optically clear finish on monocrystalline SiC material where the same size of diamond abrasives for lapping and polishing steps allows to carry out stock removal lapping and polishing processes on a single platform (machine) without concern of cross-contamination and making it as a very cost-efficient and high-throughput polishing process for SiC seed crystals and substrates.

Dynamic characteristics of abrasive grains and machined surface features for variable axis diamond grinding of quartz glass

There is a fine application prospect for multi-axis grinding of hard and brittle materials with diamond ball end tool. The effects of tool inclination angles and grinding modes of multi-axis grinding of quartz glass on the dynamic characteristics of the diamond abrasives, surface topography, surface fragmentation phenomenon, and surface roughness were investigated in this work. Material removal characteristics and surface formation conditions would be significantly affected by the effective cutting speed, material stress characteristics, and movement space path derived from different grinding modes and tool inclination angles. The surface texture direction is mainly determined by feed direction of the cutter and initial cutting moment and geometry feature of the engaged diamond abrasives. The surface fragmentation phenomenon of the formed surface is apparent when the corresponding surface roughness values are relatively larger. The machined surface with significant surface fragmentation phenomenon is mainly produced by materials' brittle fracture modes, such as larger positive lead and smaller negative tilt under conventional grinding and smaller negative lead angles and larger positive tilt angles under down grinding. Ideal surface evenness could be obtained by using lead or tilt 0° for conventional and down grinding. The ground surface with smaller surface roughness could be produced when employing tool postures, such as negative lead or positive tilt under conventional grinding and positive lead or negative tilt under down grinding condition.

Shear Thickening Polishing of Black Lithium Tantalite Substrate

To achieve high efficiency in the polishing process to obtain a high surface quality of black LT substrate (a kind of soft brittle material), shear thickening polishing (STP),which is a “gentle” finishing process developed in recent years, was employed in this study. The influence of three key parameters in the STP process including polishing speed, diamond abrasive size and diamond abrasive concentration were analyzed. To investigate the potential mechanical effect of the nanometre abrasive, nano-SiO2 abrasive particles were added in the slurry, and the concentration of SiO2 abrasive was also taken as a factor. Taguchi method was utilized to evaluate the influence of the four factors and optimize the polishing conditions. The surface roughness (Ra/Rz) was used as the evaluation index, and the optimized polishing conditions were verified through experiments. Diamond abrasive size has the most significant effect on Ra/Rz, followed by diamond abrasive concentration and then SiO2 concentration, as the polishing speed has been selected and limited in a small variation rang according to the previous study. Based on the S/N average response analysis, the surface quality is the best under the conditions with 8000# diamond abrasive, 5 wt% diamond abrasive concentration, 90 rpm polishing speed and 10 wt% SiO2 concentration. After 4 min polishing, the surface roughness Ra/Rz is reduced rapidly from 200.5/1374.6 to 4.2/22.1 nm without embedded abrasive particles on the surface of the black LT substrate. It also shows that the mechanical effect plays a dominant role in the material removal. A certain amount (10 wt% in this study) of nano-SiO2 can reduce friction between solid colloidal and workpiece, and helps to improve surface quality.

Review of Silicon Recovery and Purification from Saw Silicon Powder

The demand for crystalline silicon wafers is continuing to increase. It is inevitable that high-purity silicon will be lost as loose abrasive slurry silicon powder (LASSP) and diamond wire saw silicon powder (DWSSP) during the process of wafer preparation. For this reason, some advanced processes or methods require further development to solve the problems of the high production cost, silicon wafer shortage, and environmental pollution caused by these silicon resources. Some processes and technologies for silicon recovery and purification from LASSP and DWSSP are comprehensively reviewed in this paper. These investigations inform some anticipated technological trends and required improvements, and encourage the development of technological solutions. Furthermore, the authors propose that high-purity silicon for industrial implementations can be recycled from LASSP and DWSSP via a combined process of an acid leaching pretreatment and a high-temperature treatment. Additionally, some existing deficiencies and areas that require enhancement are also proposed for improved impurity removal and silicon recovery with a higher process efficiency.

Technology of Production of Diamond-Abrasive Composites with Metal Matrix

The prospects of using the method of explosive pressing for solving urgent problems of creating high-performance diamond composites for instrumental purposes on binders of powders of fairly cheap materials are substantiated. Purpose of this work is to develop the technology of diamond-abrasive composites synthesis from powders mixtures of natural diamond and widespread low-cost iron-carbon alloys which combines explosive pressing and subsequent short-term high-temperature heating. The processes of varying the compositions of diamond-metal powder mixtures, the parameters of their explosive pressing and the modes of subsequent heat treatment of the resulting compacts are studied. It is shown that the use of explosion energy at the stage of powder briquetting opens up new opportunities for the production of high-performance diamond-containing materials with a matrix of iron-carbon alloy powders. This is due to the specifics of the explosive action which results in the activation of the bonding material which becomes obvious with further high-temperature heating in its intensive hardening and acceleration of diffusion processes. It is revealed that the shock waves create thermobaric conditions that allow for better preservation of the diamond component than with traditional methods of sintering. Samples of abrasive diamond composites with wear resistance corresponding to the level of wear resistance of industrial diamond dressers but with half the consumption of diamond raw materials were obtained.

Mechanical properties of toothpastes with diamond abrasives.

The aim of this study was to evaluate and compare surface roughness, gloss, and color change of dental enamel after being brushed with toothpastes containing diamond powder and traditional abrasives. Seventy enamel slabs were derived from 70 bovine incisors. The slabs were brushed with six different toothpastes and artificial saliva as a negative control. The specimens were then stained with black tea mixed with citric acid (3 days, pH = 4) and again brushed with the same toothpastes. Ra (contact profilometer), gloss (glossmeter), and color (CIE L* a* b* system) values were measured after each step. Emoform-F Diamond (contains diamond powder and traditional abrasives) offered significantly the best improvement of Ra and gloss values after the first brushing sequence and the best recovery of the brightness of enamel after staining and second brushing sequence (P < .05). AMC 2.5 (contains only diamond powder as abrasive) was not able to offer such improvement. Diamond powder as an additional abrasive in toothpastes could be able to offer a further improvement of Ra , gloss, and color values of enamel.

In vivo evaluation of machining forces, torque, and bone quality during skull bone grinding.

This study investigates neurosurgical bone grinding with varying parameters on skull bone using a miniature grinding burr. Three process parameters, namely, rotational speed, feed rate, and depth of cut, have been investigated at three different levels in the terms of tangential force, thrust force, and torque generated during grinding. The results revealed that as the rotational speed is increased, the cutting forces and torque showed a decreasing trend. Nevertheless, the increase in feed rate and depth of cut leads to the escalation in response characteristics. The best parametric combination for minimum cutting forces and torque is as follows: rotational speed = 55,000 r/min, feed rate = 20 mm/min, and depth of cut = 0.50 mm. Morphological analysis reveals cracks in the bone's surface at a higher feed rate. Furthermore, delamination and cutting streaks are also visible on the surface of the bone after grinding. Energy-dispersive spectroscopy and elemental mapping of the tool after bone grinding indicate the accumulation of the bone chips in the successive diamond abrasives. The outcomes of the study will be beneficial for the neurosurgeons in understanding the effect of various process parameters on cutting force, toque, microcracks, and bone's regeneration ability during surgical bone grinding.

Silicon nanoparticle generation and deposition on glass from waste silicon powder by nanosecond pulsed laser irradiation

Silicon nanoparticles can be used for fabricating electrodes in high-performance lithium ion batteries and other high value-added products. Currently, silicon nanoparticles are fabricated by pulsed laser irradiation of single-crystal silicon wafers in water. In this study, we proposed silicon nanoparticle generation by using a nanosecond pulsed laser to irradiate waste silicon powder which is disposed from wire-saw slicing processes of silicon ingots. The laser-induced nanoparticles were backward-transferred and deposited on a glass substrate. It was found that the morphology and amount of the deposited nanoparticles was strongly dependent on the distance between the glass substrate and the waste silicon powder target. Raman spectroscopy showed that the silicon nanoparticles were crystalline, and the average size was ~10 nm. The obtained silicon nanoparticles had high purity, as the diamond abrasives included in the waste silicon powder were removed through oxidation and vaporization during laser irradiation.

Effects of compound diamond slurry with graphene for lapping of sapphire wafers

Recently, sapphire has been used in a wide range of applications including optics, consumer electronics, and especially the rapidly growing LED wafer manufacturing. This paper investigates effects of a novel compound slurry composed of micron scaled diamond abrasives and various nano-platelets of graphene oxide (GO) for improving lapping performance of c-plane single-crystal aluminum oxide (Al2O3) sapphire wafers. Four kinds of graphenes including GO, reduced graphene oxide (RGO), ML-RGO (laminate), and MF-RGO (few-layer) are added into the diamond slurry to achieve compound slurries. Those compound slurries have been prepared with various graphene weight fractions in the range of 0.3 to 2.0 wt%, by LP (low power) or HP (high power) ultrasonication with different time spans in the range of 10 min to 48 h to adjust size of GOs. For the lapping process conducted by 10-min HP ultrasonicated GO (2.0 wt%)/diamond slurry, combination of medium down force pressure and the highest platen rotation speed of 45 kPa/80 rpm results in highest material removal rate (MRR) of 926.73 nm/min, which is 324% higher than MRR by pure diamond slurry. It is caused by high reactivity of GOs with sapphire wafer. As lapped at pressure/speed of 45 kPa/70 rpm by ultrasonicated GO (0.5 wt%)/diamond compound slurry, the average surface roughness Ra of wafer can reach 7.19 nm, which is 0.7% lower than 7.24 nm by pure diamond slurry. Experimental results demonstrate that the optimized planarization of sapphire wafer with high MRR and low surface roughness can be achieved using the GO compound slurry when the mechanical removal effect and the chemical reaction mechanism are in synergistic equilibrium. The XPS and EDS analyses clearly support the material removal model that a reactant aluminum carbonate layer and a residual carbon layer exist and both are efficiently removed by diamond abrasives. Results of this study can be applied to further explore high volume production of CMP of sapphire wafers.

Frequency coupling design of ultrasonic horn with spiral slots and performance analysis of longitudinal-torsional machining characteristics

Longitudinal-torsional (L-T) vibration in rotary ultrasonic machining (RUM) can further reduce the cutting force and improve the machining efficiency compared with the single longitudinal vibration in RUM. In this study, an ultrasonic step horn with spiral slots using the principle of mode conversion was designed to realize L-T vibration. The torsional amplitude to longitudinal amplitude (AT/AL) ratio is proposed to quantify the efficiency of mode conversion. Moreover, a simulation method was used to carry out the frequency coupling design of the ultrasonic horn with spiral slots. The influence of the step position and slot position with a spiral angle of 52° on the resonant frequency and amplitude of the ultrasonic horn were analyzed, respectively. Based on the simulation results, ultrasonic horns with different AT/AL were designed and fabricated. Finally, the results obtained through experiments with milling glass plane revealed that the cutting force was reduced by 48–73%, while the surface quality improved compared with single longitudinal vibration when the torsional vibration is coupled with the longitudinal vibration in RUM. The reasonable AT/AL ratio could effectively reduce the cutting force when the synthetic amplitude was the same. This indicates that the L-T vibration changes the trajectories of the diamond abrasives, which improves the machining performance.

Diamond abrasive based cutting tool for processing of advanced engineering materials: a review

Abstract The use of abrasives for grinding was first noticed in ancient Egypt in 2000BC. Quartz was the only abrasive known at that time. Further, emery, garnet and diamond were used as the other abrasive materials for grinding as per the need of various manufacturing processes. Diamond has been recognized as an alternate to various other available abrasive materials for grinding and finishing processes in last two decades. The machining of advanced materials such as titanium alloys, nickel alloys, heat treated steel, high strength temperature resistant alloys etc, resulted in the development of new machining processes, known as hybrid machining processes. These processes involve various new tools such as metal bonded diamond grinding wheel, diamond drill bits etc. and these are most widely accepted nowadays by the researchers in micro-machining field. In present paper, attempts have been made to do an exhaustive review of various advancements in the machining technology using the diamond abrasive based tools. Diamond abrasive tools are widely being used by various researchers in hybrid machining processes such as EDDCG, EDDFG, EDDSG, ECDG, ECDD etc. This paper illustrates the history of diamond abrasives and its use in recent advancements in the manufacturing technology till now with an overview of various manufacturing methods of the diamond abrasive based tools

Preparation, microstructure analysis and performance evaluation of bonded magnetic abrasives

The traditional edged tool for machining is uneconomical for harder and difficult to machine materials. In view of the seriousness of this issue, the newly unconventional fine finishing process i.e., magnetic abrasive flow machining (MAFM) has been developed. However, the major constraint in wide spread adoption of this technology is the exorbitant cost of magnetic abrasives, which acts as a cutting tool in MAFM. In this paper, to improve the finishing performance, iron (Fe) powder mixed with diamond abrasives were prepared as bonded magnetic abrasives. These magnetic abrasives were prepared by mechanical alloying followed by annealing of diamond abrasives of 52 μm grit size and Fe powder of 49 μm grit size. These abrasives were micro-structurally analysed. The results indicate that densification increases and porosity decreases with increasing temperature. Further it was clarified that the prepared bonded magnetic abrasives has potential performance as the new magnetic abrasives for fine finishing.

A fracture mechanics approach to enhance product and process sustainability in diamond wire sawing of silicon wafers for solar cells through improved wire design

By decreasing the subsurface damage in silicon wafers produced by diamond wire sawing, the mechanical strength of wafers can be increased, and the amount of silicon to be etched in subsequent manufacturing steps can be minimised, enhancing both product and process sustainability. Apart from the sawing process parameters, the subsurface damage in as-sawn silicon wafers is influenced by the design of the diamond wire. We present a fracture mechanics approach for the design of fixed abrasive diamond wires used in wire sawing of silicon wafers for solar cells. Starting from an allowable damage (crack) depth, indentation fracture mechanics and contact analysis are used to determine the wire design parameters, namely the grit protrusion and peripheral distribution of diamond abrasives. The improved wire design can reduce subsurface damage and thereby improve the surface integrity (product sustainability), and reduce the processing time and chemicals used in the subsequent saw-damage removal step (process sustainability).

A bow-free freestanding GaN wafer.

For applications as high-brightness light-emitting-diodes, a bow-free freestanding gallium nitride (GaN) wafer 2 inch in diameter and ∼185 μm in thickness was fabricated by process-designing pit and mirror GaN layers grown via hydride-vapor-phase epitaxy, laser lift-off, N-face polishing of the pit GaN layer, and three-step polishing of the mirror GaN layer using 3.0 μm-, 0.5 μm-, and 50 nm-diameter diamond abrasives and by inductively-coupled-plasma reactive-ion etching. The considerably large concave shape of the GaN wafer could be decreased by controlling the removal amount of the Ga-face mirror layer during the first step of the polishing process, which approached a bow-free shape or changed with further polishing; this well correlated with the residual stress of the polished GaN wafer.