Diamond Grits Research Articles

Numerical Modelling of Stress/Strain Field Arising in Diamond-Impregnated Cobalt

Abstract The paper presents results of computer simulations of the stress/strain field built up in a cobalt matrix diamond impregnated saw blade segment during its fabrication and after loading the protruding diamond with an external force. The main objective of this work was to create better understanding of the factors affecting retention of diamond particles in a metallic matrix of saw blade segments, which are produced by means of the powder metallurgy technology. The effective use of diamond impregnated tools strongly depends on mechanical and tribological properties of the matrix, which has to hold the diamond grits firmly. The diamond retention capability of the matrix is affected in a complex manner by chemical or mechanical interactions between the diamond crystal and the matrix during the segment manufacture. Due to the difference between the thermal expansion coefficients of the diamond and metallic matrix, a complex stress/strain field is generated in the matrix surrounding each diamond crystal. It is assumed that the matrix potential for diamond retention can be associated with the amount of the elastic and plastic deformation energy and the size of the deformation zone occurring in the matrix around diamonds. The stress and strain fields generated in the matrix were calculated using the Abaqus software. It was found that the stress and strain fields generated during segment fabrication change to a large extent as the diamond crystal emerges from the cobalt matrix to reach its working height of protrusion.

Investigation of chipping and wear of silicon wafer dicing

Wafer dicing chipping and blade wear processes in transient and steady stages were investigated. Dicing blades with two different diamond grit sizes were used to cut wafers. In the cutting experiments, the dicing blades with two different diamond grit sizes were used to cut wafers and for a given type of wafer, the cooling water temperature, cutting feed speed, and rotational speed were fixed. The chipping size, blade surface wear area and surface roughness of the wafer were measured at cutting distances of 50, 150, 300, 975, 1350, and 1900m, respectively. Cutting debris of cutting distances of 300m and 1900m was collected and analyzed. The correlation between blade surface properties and chipping size was investigated. Based on this experimental system, attention is to pay to examine the correlation between blade surface properties and chipping size for transient stage and steady stage. In transient stage, the roughness of dicing blade increases rapidly. This will rapidly increase the chipping size. In steady stage, the chipping size decreases slowly with the decreasing roughness of blade surface. This concludes that blade surface condition is an important factor that affects the chipping size. Moreover, in transient stage, diamond grits that are salient or less bonded to the blade detach leave caves on the blade surface which increases surface roughness of the blade and the chipping size. In steady stage, the heights of grits become even and the chipping size decreases accordingly.

Generation of diamond wire sliced wafer surface based on the distribution of diamond grits

Diamond wire sawing is one of the abrasive machining processes. The cutting tool is a tiny steel wire coated with a large number of diamond grits. Although wire saw is widely used for slicing hard and brittle materials, it is still very complicated to be analyzed and understood because of the unique characteristics of the wire. This study takes the advantage of modern computer technology to simulate the wire sawing process kinematically. The wire parameters with random features including the sizes and positions of the abrasive grits have been considered in the wire model. Based on process parameters, the cutting process was simulated by mapping the cutting profile into the array representing the workpiece. The sliced surface topography was then generated depended on interaction between the active abrasive grits and the workpiece. Experiment was conducted to verify the simulation results. The effects of process parameters including wire speed, feed rate, the size and distribution of the diamond grits to the sliced wafer surface quality are also investigated. The approach proposed in this study makes it possible to investigate the effect of process parameters and diamond grits to improve the practical wire sawing process.

Surface and subsurface damage characteristics and material removal mechanism in 6H-SiC wafer grinding

In this paper, a cross-sectional cleavages microscopy method was used for subsurface damage detecting of 6H-SiC wafer grinding. The OLS4000 laser confocal microscopy was used to observe the surface morphology and subsurface cracks. The surface and subsurface damage characteristics and material removal mechanism in different grinding conditions were analysed. The results show that the major types of surface damage in SiC grinding are chipping pits, plough scratches and smear products. Lateral and median cracks are found in the subsurface. The grinding surface quality and the depth of subsurface crack can be altered by changing the maximum undeformed chip thickness that can be adjusted with different diamond grit sizes, feed rates and wheel speeds. With the decreasing the maximum undeformed chip thickness, the grinding surface roughness decreased and a trend of a brittle–ductile transition was observed.

Microstructural analysis of metal‐bond diamond tools in grinding of flat glass

This research is concerned with the structural analysis of the diamond grinding wheels. The effects of diamond mesh size are investigated using two types of grinding tools. One of them is iron based with diamond grits, the other one is copper based with diamond particles. Two kind of diamond grit size was used for the microstructure analysis. The microstructure analysis of the grinding wheels is presented, based on the spectrum results using scanning electron microscope (SEM) and energy dispersive X‐ray analysis device (EDX). In comparison between the Cu‐based and Fe‐based diamond grinding wheels, iron based diamond tool is detected to have a longer lifetime than the Cu‐based one.

New CMP Pad Conditioners with Increased Number of Diamond Tips for Longer Dressing Life

With the relentless progression of Moore's Law toward sub-virus sized (e.g. 28 nm) node of interconnected circuitry (IC), and also the planned debut of 450 mm wafers for 2015, CMP reaches a bottleneck that the polishing of the delicate IC wafers must be achieved by effective deglazing of pad with the extended life of dressers (diamond disks). The conventional diamond disks are made by bonding individual diamond grits by either brazing or electroplating. Brazing can allow higher protrusion of diamond tips that facilitate the deglazing process, but the tips leveling cannot be controlled due to the melting of the braze powder at high temperature (e.g. 1000 C). On the other hand, electroplating may improve the leveling of diamond tips, but the protrusion is limited (e.g. 50 microns) so the deglazing of metal layers cannot be achieved efficiently. Moreover, all pad conditioners today used an array of diamond grid that was invented by Dr. James Sung back in 1997. Due to the alignment of the diamond tips, the pad dressing may not be uniform so the wafer polishing could not be uniform. Worse still, deep penetrating diamond tips may be chipped and cause scratches on expensive IC wafers. Here we introduce the world's first diamond disks that are brazed with amorphous alloy without using powder and binder. Amorphous alloy can allow uniform melting across the diamond disk surface and also avoid the presence of residue carbon from charring of binder. Additionally, we use concentric rings of diamond placement that avoids stress concentration on certain diamond tips. Due to the improved process design, we have demonstrated a significant increase of working diamond tips from conventional number of a few hundreds to over one thousand. This can be seen by indenting diamond disks on colored films spread on a flat platform. Our diamond disks have been tested on CMP process with high removal rate of IC wafers and we expect that the life time may be at least twice of conventional diamond disks. This can allow the dressing of large pad such as that for polishing future 450 mm IC wafers.

Brazed Diamond Micropowder Bur Fabricated by Supersonic Frequency Induction Heating for Precision Machining

The common brazed diamond micropowder bur fabricated in a vacuum furnace produces an even brazing alloy surface. The small brazed diamond grits show low outcropping from the brazing alloy surface, and the chip space between them is small. The bur shows a low grinding efficiency and poor heat dissipation. In this study, a brazed diamond micropowder bur was fabricated by supersonic frequency induction heating. The method afforded a fluctuant surface on the brazing alloy. The brazed diamond grits with an outcropping height distributed uniformly on the fluctuant surface. The fluctuant surface showed a certain chip space. These characteristics of the tool increased the grinding efficiency and decreased the temperature of the grinding arc area. The roughness R a of the ceramic tile surface trimmed by the tool cylinder was between 0.09 and 0.12 μm. In the first 90 min, the decrease in the weight of the ceramic tile ground by the tool cylinder was higher than that ground by the tool fabricated in a vacuum furnace. When the ceramic tile was cylindrically ground, the temperature of the grinding arc area measured using a thermocouple remained below 70 °C.

Development and Application of a Cutting - Abrasive Impregnated Diamond Bit

Igneous rocks of Junggar Basin are hard, strong abrasive and poor drillability. ROP is low in drilling these rocks, and drilling cycle is long, which seriously affect the process of exploration and development in the Carboniferous reservoir. Considering the igneous rock formation characteristics and the drilling problems, using PDC impregnated diamond high strength, super abrasion as the main rock breaking device, a new type of cutting and grinding of diamond impregnated bit was developed. This bit has the following characteristics: Compound cutting structure with blades and cylindrical Impregnated cutters; big nozzle in the center + deep radiation water slot hydraulic structures; Natural diamond and TSP lengthened gauge design; Selection of 40/50 mesh diamond grit, mix two kinds of inserts with diamond concentration 70%.The bit has the combination of impregnated bit and PDC drill bit technical advantages, which improve the bit adaptability to the formations. Hassan3 Carboniferous igneous formations field test shows that: average ROP is 0.71m / h, single bit footage is 86.5m, which increased by about 20% and 302% respectively compared with high efficient three-roller bits. The success usage of this bit in Hassan 3 provide an effective means for high quality fast drilling in Junggar Basin igneous rock formation.

Analysis on the Thermal Stress of Brazed Diamond Bit During Cooling Process

Brazed diamond process is a new green manufacturing technology, and metallurgical bonding with the mixed chemical bond in the transition layer can be achieved between the diamond grits and its matrix. The high brazed temperature (970-1050 ̊C) and the expansion coefficient difference between the matrix and moulds cause thermal stress harm to the bit quality during cooling. To study the brazed diamond bit, a thermal elastic mechanics model of the matrix and the graphite mould was built based on the analysis of cooling process. The radial and tangential thermal stress between the matrix and the core mould were obtained. The study is shown as follows: the radial stress and the tangential stress approximate to a linear relationship with the temperature difference and the expansion coefficient difference. The thinner the matrix thickness becomes, and the greater the tangential stress increases obviously. Generally, the radial stress is smaller than the tangential stress for the special bit.

Influence of Surface Integrity on the Tribological Performance of Cold Forging Tools

In forming industry the tool is fundamental for the profitability, as it determines efficiency of cold forging process. In this regard, the tool surface has a distinctive influence on the tribological conditions and thus on the occurring tool stresses. The present study investigates the influence of different fine machining strategies on the tribological performance of cold forging tools made of WC-Co cemented carbide by applying the double cup extrusion test.The results reveal that a peened surface causes higher friction in the forming process compared to polished tool surfaces up to 100%. For polishing a minimum in friction is found for the diamond grit D 6μm with a friction factor of m = 0.03.

Study on Preparation and Cutting Performance of a New Diamond Grinding Fiber

A new kind of diamond fiber with a certain length to diameter ratio and macroscopic dimensions(1mm×1mm×10mm)by powder injection molding and buried sand sintering method is designed and obtained. The new diamond fiber uses the Na2O-Al2O3-B2O3-SiO2 system ceramics adding a certain amount of iron group metal Co as the diamond abrasive ceramic-metal bond. Different from the traditional diamond grits, this new kind fiber has orderly arrangement in accordance with the requirements and can prepare ordered diamond fiber grinding wheel. Then the flexural strength, hardness and other properties of the diamond fiber are measured, and the contrast test between single diamond fiber specimen and normal ceramic wheel processed ultrahard material SiC enhanced high silicon aluminum alloy is conducted. The results shows that the new diamond fiber prepared has a certain strength and hardness; ceramic-metal bond in the new fiber gives better wet-ability and stronger holding force to the diamond abrasive particle and makes it difficult to fall off; meanwhile, the new diamond fiber has good processing performance and the workpiece has good surface quality, which can achieve precise machining SiC enhanced high silicon aluminum alloy. Effective diamond abrasive particles have a high percentage in the new diamond fibers, and the distribution is uniform. The abrasive particles have a good quality of high uniformity of protrusion height, and have a high utilization with large amount of abrasive particle participated in cutting. Diamond in the diamond fibers realizes three-dimensional arrangement, which means that the lower diamond can continue to play its cutting ability when the upper abrasive loses cutting ability or falls off due to bearing greater friction and extrusion pressure.

A Roughness Study of Ytterbium-Doped Potassium Yttrium Tungstate (YB: KYW) Thin-Disk Femtosecond Ablated Dentin.

The aim of this study was to evaluate the morphological changes and quantitatively assess the roughness of dentin after the ablation with a Ytterbium-Doped Potassium Yttrium Tungstate (YB: KYW) thin-disk femtosecond pulsed laser of different fluences, scanning speeds and scanning distances. Twelve extracted human premolars were sectioned into crowns and roots along the cementum-enamel junction, and then the crowns were cut longitudinally into sheets about 1.5 mm thick with a cutting machine. The dentin samples were fixed on a stage at focus plane. The laser beam was irradiated onto the samples through a galvanometric scanning system, so rectangular movement could be achieved. After ablation, the samples were examined with a scanning electron microscope and laser three-dimensional profile measurement microscope for morphology and roughness study.With increasing laser fluence, dentin samples exhibited more melting and resolidification of dentin as well as debris-like structure and occluded parts of dentinal tubules. When at the scanning speed of 2400mm/s and scanning distance of 24μm, the surface roughness of dentin ablated with femtosecond pulsed laser decreased significantly and varied between values of dentin surface roughness grinded with two kinds of diamond burs with different grits. When at the scanning speed of 1200mm/s and scanning distance of 12μm, the surface roughness decreased slightly, and the surface roughness of dentin ablated with femtosecond pulsed laser was almost equal to that grinded with a low grit diamond bur. This study showed that increased laser influence may lead to more collateral damage and lower dentin surface roughness, while scanning speed and scanning distance were also negatively correlated with surface roughness. Adequate parameters should be chosen to achieve therapeutic benefits, and different parameters can result in diverse ablation results.

The effects of porcelain finishing and polishing systems on the surface roughness of feldspathic porcelain: An in vitro study

Introduction: This in vitro study deals with the efficiency of surface polishing systems after the glaze layer of the ceramic has been altered using a medium grit diamond to simulate the chairside adjustment of a restoration. Materials and Methods: Forty porcelain discs measuring 10 mm × 3 mm with a metal substructure of 10 mm × 1 mm were used. Ceramco 3(ultra-low fusing feldspathic porcelain) porcelain system was used to fabricate the discs on the metal substructure. A medium grit diamond was used to simulate the chairside adjustment procedures. Ten samples were glazed (control group) and 30 samples were finished and polished using three finishing and polishing agents. (experimental group; Shofu Ceramaster, Kohinoor diamond polishing paste and Sof-Lex discs).These 40 samples and the initial roughened samples were subjected to a profilometer evaluation to obtain results in Ra (Average roughness in µm) and Rz (Mean maximum peak -to-valley height in µm). Results: One way ANOVA revealed a statistical significant difference amongst Ra values of the group. Amongst the finished and polished group of samples, the samples polished with Shofu Ceramaster diamond-impregnated silicon showed the highest efficiency among the three finishing and polishing systems followed by samples polished with Kohinoor L highly filled diamond polishing paste and the least efficient polishing system was the samples polished using Sof-Lex discs. The Rz (Mean peak-to-valley height) values showed the same results as the Ra values. Conclusion: The study concluded that among the three finishing and polishing systems tested, Shofu Ceramaster diamond impregnated silicon rubbers are the most efficient with significant differences in surface roughness compared to roughened samples

Investigation of CFRP machining with diamond abrasive cutters

Diamond abrasive cutters are more and more used for industrial applications of CFRP laminate machining, due to their resistance to abrasion and low cost. The objective of the approach is to improve productivity during trimming operations, by choosing adapted tools and cutting parameters. The objective of this article is to determine to what extent feedrate and spindle speed can be increased. To do so, specific cutting energy (Esp) and cutting forces are studied. Designs of Experiments and ANOVA are performed in order to analyze the influence of tool (grit size, level of nickel and diameter) and process (feed per revolution and cutting speed) parameters. It shows that high cutting speed is favourable to the cut due to thermal effects. Conversely, the study of specific cutting energy reveals that the feed increase is limited by diamond grit size and level of nickel due to the saturation of the tool intergrit space.

Rod-like brazed diamond tool fabricated by supersonic-frequency induction brazing with Cu-based brazing alloy

Supersonic-frequency induction heating was used to fabricate a rod-like diamond tool brazed with a Cu-based brazing alloy in order to control the dropping of liquid brazing alloys that takes place in other brazing technologies. The brazing alloy can be spread evenly and the diamond grits can be correctly exposed on the rod-like brazed diamond tool by using a proper induction brazing technique. Dissolution, diffusion, and chemical recombination took place between the diamond grits and the brazing alloy, and a diffusion band approximately 30μm wide was observed between the brazing alloy and the steel substrate. This demonstrates that metallurgical bonding occurred both at the interface of the diamond grits and the brazing alloy and at the interface of the brazing alloy and the steel substrate. A boring test of the brazed diamond drill showed that the total grain fracture percentage of the diamond grits was higher than the falloff percentage.

Optimization of diamond grinding conditions for steel R6M5F3 allowing for the process unsteadiness

The paper addresses optimization of machining conditions in diamond grinding of steel R6M5F3 taking into account the process unsteadiness. The optimization is accomplished for plunge-cut grinding by the elastic mode with a constant workpiece-to-wheel pressing force, the kinematics of the process being similar to the rigid-mode one. The region of possible machining conditions for an early stage of the elastic-mode diamond grinding is considered in the coordinates “workpiece speed—workpiece pressing force”. The workpiece speed is determined for a specified machined surface roughness. The workpiece pressing force is chosen to be minimal based on the condition of ensuring no phase-structural transformations in the surface layer of the workpiece material, no diamond oxidation, and no destruction of diamond grits. The process unsteadiness was allowed for through the use of the equations describing the time variation of the current limited cutting ability of the grinding wheel.

The effects of solder alloys on the morphologies and mechanical properties of brazed diamond grits

In this work, diamond grits are brazed with either Ag–Cu–Ti alloy or Ni–Cr alloy. Variations in the morphology of the brazed diamond grits, such as graphitization, erosion, microcracking and fracture, are observed. The compressive strength and thermal toughness index (TTI) of the brazed diamond grits are evaluated. The results obtained show that the morphologies of the original, unaltered diamond grits are similar to those of the brazed diamond grits. When the diamond grits were brazed using the Ag–Cu–Ti alloy, several disadvantageous phenomena, i.e., graphitization, erosion, microcracking, and fracture, were not observed, and the compressive strength and the TTI values of the brazed diamond grits were decreased only slightly. However, when the diamond grits were brazed with the Ni–Cr alloy, surface graphitization, erosion, microcracking, and fracture of the brazed diamond grits resulted, in addition to a significant reduction of the mechanical strength of the brazed diamond grits.

Study on the Machining Parameters in Polishing Single-Crystal SiC Wafers with SG Films

In this paper, diamond abrasive SG films were prepared by means of sol-gel technology for polishing single-crystal SiC wafers. The effects of machining parameters on processing quality including pressure, rotating speed and polishing time were investigated, respectively. The results indicated that the surface roughness decreased with increasing polishing time. While for pressure and rotating speed, there were inflections existing. Polishing SiC wafer under optimized machining parameters, an ultra smooth surface with the roughness of 3.7 nm could be achieved using 40 μm diamond grits.

Low‐temperature degradation of a Y‐TZP ceramic after surface treatments

The purpose of this study was to evaluate the influence of zirconia surface treatments on low-temperature degradation (LTD). Disc-shaped specimens were subjected to one of four surface treatments, denoted as C (control-no surface treatment), Si (air abrasion with 30 µm silica-modified alumina particles), Al (air abrasion with 30 µm alumina particles), and Gr (grinding with 120 grit diamond discs). Half of the samples were submitted to autoclave treatment for 12 h (127°C, 1.5 bar). Samples were characterized by x-ray diffraction and profilometer analysis and were subjected to biaxial flexural strength test. All of the groups exhibited an increase in the amount of monoclinic phase (m-phase) after LTD. The t→m transformation was remarkable for the specimens from the C group, which also exhibited a significant increase in strength. The Gr group also exhibited an increase in strength but lower initial roughness, which probably suppressed LTD on the zirconia surface. The specimens subjected to air abrasion exhibited higher initial amounts of m-phase and a small increase in m-phase after LTD; the strength was not affected in these groups. The effects of LTD were different with each surface treatment applied. Apparently, LTD may be suppressed by smoother surfaces or the presence of an initial amount of m-phase on zirconia surface.

Finish machining of mirror-like diamond surfaces using a composite electroplating in-process sharpening method

Finishing mirror-like surfaces on chemically vapor-deposited diamond film using an in-process composite electroplating of diamond grains onto the tool surface, the tool can maintain its sharpness in a grinding process. The effect of diamond grit size of the tool on the grinding characteristics of diamond film is investigated. To promote optimum grinding efficiency, a high variation rate in the surface roughness of diamond film and a small growth rate in the coating thickness are desired. A distribution model of the diamond grits in the coating layer is deduced, and a composite electroplating in-process sharpening grinding mechanism is developed using a body-centered tetragonal structure. A two-stage composite electroplating in-process sharpening grinding procedure is used to grind the diamond film. A grit size of 25 µm is selected to conduct the composite electroplating in-process sharpening grinding for 30 min at an initial surface roughness of 1.1 µm. Then, the operating conditions are switched to a grit size of 3 µm and a grinding time of 180 min, and a mirror-like surface on the diamond film with an average surface roughness of 0.03 µm is obtained.