Diamond Grinding Tools Research Articles

Grinding quality evaluation and removal mechanism of resin-coated SiC and 2.5D-C-SiCs surface strategies

The paper proposes a strategy to enhance the processing quality of SiC and 2.5D-C-SiCs by coating epoxy resins on the material surface and edges, and then using resin-bonded diamond grinding tools for grinding. Epoxy resin acts as a protective layer that can absorb impacts during grinding, reduce damage, and thus improve the processing quality of the surface and edges. The experimental results show that resin coatings can effectively improve the surface quality of SiC and 2.5D-C-SiCs. By adjusting the RT and RE, processing parameters can be further optimized to achieve the best surface quality. This study provides new ideas and methods for enhancing the surface quality of SiC and 2.5D-C-SiCs materials, with important application prospects and practical significance.

Numerical simulation and experimental researches on different abrasive grain arrangements of monolayer diamond grinding tools fabricated by HFCVD method

The hot filament chemical vapor deposition (HFCVD) method has been used to fabricate monolayer diamond grinding tools, whose abrasive grain arrangements can be achieved by patterned masks. The orderly arrangement pattern of abrasive grains can improve the grinding trajectory density of abrasive grains and reduce the workpiece surface roughness. In this study, the numerical simulation method is used to investigate the effect of abrasive grain pattern arrangements on the grinding trajectories and ground surface topographies, including Archimedes spiral, concentric circular, phyllotactic, disordered, and staggered patterns. The simulation results indicate that the grinding trajectory is most uniform and dense when applying the staggered pattern arrangement, and the workpiece surface roughness is lower than that of the other pattern modes. Then monolayer diamond grinding tools with five types of abrasive grain patterns are fabricated on the SiC substrate by HFCVD method. The grinding tool surface has a complete grain pattern and as-grown diamond film on the substrate is homogeneous in thickness, which is regarded as the bonding layer of the abrasive tools. EDS carbon element mapping and Raman spectra analysis reveal that the as-grown diamonds, both on substrates and seeds, exhibit high quality. Grinding experiments are performed utilizing CVD diamond grinding tools. The ground surface with a staggered pattern exhibits the lowest surface roughness without periodic grinding bands, as is consistent with the simulation results. Besides, the graphitization evaluation and worn feature statistics show that abrasive grains are of low levels of graphitization and high quantity of dynamic active grains as well as have slight abrasive grain wear and large chip space applying staggered pattern, which is the ideal abrasive grain arrangement pattern.

АНАЛИЗ МЕТОДОВ ПРАВКИ КОЛЬЦЕВЫХ АЛМАЗНЫХ СВЕРЛ НА МЕТАЛЛИЧЕСКОЙ СВЯЗКЕ

The study objective is to analyze the existing methods to dress annular diamond drills of metal bonds and to develop new schemes of dressing used for diamond grinding tools.
 The paper is devoted to solving the problem, which consists in comparing different dressing methods, analyzing their disadvantages and advantages.
 Research methods are theoretical studies of various methods of annular diamond drill dressing.
 Novelty of the work: schemes for dressing annular diamond drills of metal bonds with free abrasive are developed.
 Research results: the existing methods and schemes for dressing annular diamond drills of metal bonds are analyzed, their main disadvantages and advantages are found. Dressing schemes for the free abrasive method are developed.
 Conclusions: when drilling hard non-metallic materials with annular diamond drills, the tool loses its functionality, glares and needs forced dressing. During the analysis, existing methods and possible dressing options are considered.

Fabrication of PCD face grinding wheel with positive rake angle by femtosecond laser and its performance evaluation in cemented carbide grinding

Super-hard abrasive grinding is considered to be the main approach to realize precision and ultra-precision machining of difficult-to-machine materials such as cemented carbide, engineering ceramics, titanium alloys and superalloy materials encountered. However, heavy grinding force, high grinding temperature and poor surface integrity are prone to be encountered in conventional negative rake angle grinding of difficult-to-machine materials. In response to these problems, a novel concept of positive rake angle grinding is first proposed and an abrasive grain regularly arranged binder-less polycrystalline diamond face grinding wheel with positive rake angle has been designed and fabricated by femtosecond laser ablation. To evaluate the grinding performance of the face grinding wheel with positive rake angle, grinding experiments of YG8 cemented carbide are conducted and compared with the traditional electroplated diamond grinding tool with equivalent abrasive grain dimension and distribution. The results show that compared with the conventional negative rake angle grinding, the normal and tangential forces in positive rake angle face grinding are reduced by 30.3 % ∼ 36.4 % and 21.1 % ∼ 29.3 %, respectively, and the ratio of normal to tangential force is reduced by 12.6 % ∼ 20.3 %. The surface roughness and average depth of subsurface metamorphic layer are also significantly smaller. The laser fabricated polycrystalline diamond face grinding wheel also has better wear resistance in the grinding of cemented carbide. Therefore, it can be concluded that better ground surface quality is obtained by the novel grinding wheel with positive rake angle. The innovative grinding method can fill the research gap on the grinding mechanism of positive rake angle grinding and further enrich the grinding theory of difficult-to-machine materials.

Finite element based 3-D modelling of residual stress in high vacuum actively brazed diamond/Ni-Cr filler/C45 steel joint

In active brazing of diamonds, high brazing temperature and difference in the thermo-mechanical properties of the diamond grain, filler alloy, and substrate lead to the development of unfavorable residual stresses in the bonding region. This residual stress can potentially cause initiation of cracks within the interfacial reaction layer formed between diamond and filler-alloy, weakening the joint. Since the diamond particles used in diamond grinding tools are micro-sized and complex in shape, it is experimentally difficult to measure residual stress at the grit-filler interface. In the present investigation, a coupled thermo-mechanical three-dimensional finite element model has been developed to predict, map, and analyse the formation of residual stresses in diamond-bond-substrate systems. The presented model uniquely differs from those in literature, which are mostly 2-D type and did not consider the presence of interfacial reaction layer between diamond and filler. A Ni-Cr-Fe-B active brazing alloy has been selected as the filler and C45 steel as the substrate in the current simulation. Chromium carbide has been considered to be the interfacial compound. The numerical simulation suggests that the maximum value of residual stresses, predominantly tensile in nature, gets shifted from the diamond to the intermetallic zone at the bond level when the interfacial reaction compound is introduced between the diamond and filler. It also establishes that orientations of diamond during its placement on substrate for brazing have significant influence on the magnitude of induced residual stress. Approximately 40 % reduction has been observed in case of hexagon-base brazed diamonds when compared to that (1620 MPa) developed on square-base brazed diamonds. Raman spectral analysis of brazed specimen was conducted to experimentally validate the numerical simulation results. Residual stress was estimated from the peak shift of D-band in the spectra. The numerically computed residual stresses were found to deviate within the range of 3–15 % of the experimentally determined values.

The effect of temperature and dwell time on diamond-WC brazed joint quality using low-melting point active Ag-Cu-In alloy

The recent demand for developing micro-pin Diamond grinding tools has gained tremendous importance in tool manufacturing industries. A successful development of these tools requires joining Diamond grits to carbide surface firmly. In this context, the present paper demonstrates the joining of Diamond grits to WC-cermet surface via brazing route using Ag-Cu-24.3In-3Ti active alloy (Incusil-ABA). All brazing experiments were conducted using a resistance type heating furnace under a highly controlled vacuum environment to eliminate contamination. Experimental findings of this investigation indicate that both brazing temperature and dwell time have significant influence on microstructure and other related properties of the alloy. Titanium present in the alloy was found to segregate towards Diamond-alloy interface. It was expected that such segregation would ensure a proper wetting by the alloy. However, the overall morphology of the brazed joint revealed that improper melting and poor wetting by alloy on cermet surface were two major challenges. The current study showcases that a careful control on brazing temperature and dwell time demonstrates a remarkable improvement in wetting characteristics and alloy morphology. It has been observed that a brazing temperature of 780 °C and dwell time of 15 min resulted in a good brazed joint morphology. The study also investigated the effect of said brazing temperature on grits physical characteristics using Raman spectroscopy. At the end, scratch test and wear characteristics of the filler are investigated in detail. The outcome of this investigation will be of immense interest to tool manufacturing industries associated with development of brazed micro-pin Diamond grinding tools using alloys having low melting point.

Influence of an Oxygen-Free Atmosphere on Process Forces and Workpiece Quality during the Surface Grinding of Ti-6Al-4V

Most manufacturing processes, such as grinding, are usually conducted in a standard air atmosphere. The oxygen within this atmosphere leads to oxidation effects on tools and workpieces when machining metal components. This is primarily a factor in the processing of titanium due to its high affinity for oxygen. The oxidation of the surface increases tool wear and reduces surface quality. Hence, this paper investigates the influence of the atmosphere on process forces and workpiece quality when grinding titanium (Ti6Al4V) with metal-bonded diamond grinding tools. To generate oxygen-free conditions in production processes, a novel approach allows an atmosphere with a very low oxygen partial pressure. Using a silane gas, which reacts with oxygen, the oxygen partial pressure, pO2, can be reduced below 10−12 mbar, equal to the oxygen partial pressure in an extremely high vacuum (XHV). The results show a significant influence of the atmosphere on the process forces. When grinding in XHV-adequate conditions, the grinding forces are reduced by 16% in the tangential direction and 50% in the normal direction on average, while the quality of the ground titanium surfaces is consistent (both atmospheres: Rz = 13–21 µm). Phase analysis via XRD revealed a distinct amount of titanium nitride (TiN) on the ground surfaces independently of the atmospheric conditions.

Influence of wire electrical discharge conditioning on the grinding performance of metal-bonded diamond grinding tools

Wire Electrical Discharge Conditioning (WEDC) is an efficient non-conventional method for conditioning metal, resin, and hybrid bonded super-abrasive grinding tools. Since the diamond and CBN grains are not affected directly by the WEDC and only the electrically conductive bond material is eroded by the process, high grain protrusions are achievable. Therefore, unlike the common mechanical conditioning methods using WEDC, the microtopography of the grinding tool can be influenced by the process parameters, directly affecting the grinding efficiency. However, the selection of WEDC process parameters is influenced by the specifications of the grinding tool, particularly the grain size and concentration. This study aims to investigate the effects of WEDC parameters and strategies on the microtopography and material removal rate of metal-bonded grinding tools, considering different grain sizes and concentrations. Additionally, the correlation between the microtopography of grinding tools conditioned by the WEDC process and their grinding efficiency was investigated by analyzing tool wear, grinding forces, and surface roughness of tungsten carbide workpieces. The results indicate that the material removal rate of the WEDC process decreases as the grain size and concentration of metal-bonded diamond grinding tools increase. Furthermore, it was observed that employing high spark energy parameters reduces the grain protrusion of grinding wheels with small grain sizes. However, the utilization of high-energy sparks is necessary to create larger spark gaps and achieve a higher material removal rate.

Dry grinding of Al-SiCP composite with patterned diamond wheel

Aluminium being soft and ductile in nature, is one of the challenging materials to grind in industrial practice. Furthermore, load-free grinding of Al-SiC composites has been the most daunting task for many of the researchers with the available tools. In the present work, the feasibility of grinding of Al-SiC particulate composite by an indigenously developed single-layered brazed diamond grinding tool having uniformly arranged abrasive grits has been investigated. The experiments were carried out in reciprocating surface grinding mode without providing any crossfeed. Dry grinding was performed with increasing order of downfeed up to 30 μm at two different grinding velocities of 30 and 40 m/s and table feed of 2 and 5 m/min. Cutting forces, specific grinding energy, and roughness of the ground surface at different cutting depths were studied to analyze the grindability of Al2124-17SiCP composite, which is, as such, known to be a sticky-abrasive material. There was no sign of wheel loading, but a hint of mechanical chip adherence on grit tips was noted at higher down feeds. Although such abrasive machining was realized without any trace of wheel loading, surface roughness was recorded to be unfavorably high due to fewer overlapping cuts and non-participation of passive grits. However, it was observed that roughness could be improved significantly with the application of suitable crossfeed.

Study on wear simulation of diamond abrasive tool for rotary ultrasonic grinding

The aim of this study is to explore the wear mechanism of diamond grinding tools in rotary ultrasonic grinding process and complete the simulation study of micro wear state of diamond grinding tools in different processing stages. Primarily, the morphology of single diamond abrasive grains is analyzed and studied, and a three-dimensional irregular abrasive grain simulation is carried out according to the morphology characteristics of diamond abrasive grains. Then, the center distance and spatial distribution law between diamond grits are obtained by calculation, and the discrete three-dimensional morphology simulation of diamond abrasive end face is completed based on the virtual lattice theory. Through the rotary ultrasonic grinding experiment, the wear form of diamond grits and the mathematical model of the wear amount of diamond grits changing with the removal amount of workpiece material are determined. The wear simulation of diamond abrasive tool with different workpiece removal is completed by using the mathematical model obtained from experiments. Last section, the number of abrasive particles in the simulation model and the wear amount of the abrasive tool are compared and analyzed with the corresponding experimental results. The above research provides a new research method for exploring the wear mechanism of diamond abrasive tools.

Three-dimensional topography modelling and grinding performance evaluating of micro-structured CVD diamond grinding wheel

Micro-structured chemical vapour deposition (CVD) diamond grinding tools are attracting increasing attention in precision grinding and micro-grinding because of their advantages in low grinding forces, high machining accuracy and good wear resistance. A well-developed wheel topography model for this kind of emerging grinding tool not only can facilitate the analysis and optimization the grinding process, but also is the essential basics for the intelligent machining. In this paper, a novel three-dimensional surface topography model of original CVD diamond grinding wheels was firstly established based on the multiple random data of the shape, size, posture and distribution of the CVD diamond grains. And the ground surface topography model was simulated depending on the established wheel model and grinding kinematics. Secondly, the models were verified by the results of grinding experiments in the means of topographical characteristics, surface roughness and PSD. Then, the influence of grinding parameters and wheel wear on the grinding performance of CVD diamond wheels was discussed. Finally, the micro-structured CVD grinding wheel models were presented by coupling different forms of micro-structures. And the effects of micro-structure parameters including widths, inclination angles, structuring ratios and types on the grinding performance of micro-structured CVD diamond wheels were investigated quantitatively. This study provides a quantitative and effective method for the design of CVD diamond grinding wheels and their surface structuring. Furthermore, the proposed micro-structured analysis method is also available for other structured grinding wheels.

Feasibility study on sharpening metal-bond metal diamond grinding tool by microwave-induced electric discharge machining

Microwave-induced electric discharge machining (MV-EDM) is an emerging machining method that can be applied to fine machining of metal materials. A feasibility analysis of the application of MV-EDM to sharpen diamond grinding tools was conducted in this study. A multiphysical simulation model for sharpening using MV-EDM was established, and MV-EDM sharpening experiments and measurements were performed to verify the accuracy of the simulation model. It was found that MV-EDM can effectively improve the protrusion height hp and does not result in severe graphitization of diamond grains under appropriate conditions. Under the conditions of a microwave power of 1 kW and a gap scale d of 0.1 mm, the hp of the diamond grain increased to 91 μm with a complete diamond crystal shape and slight graphitization. In addition, it was discovered that the gap scale d and initial protrusion height h0 had a significant effect on the protrusion height hp and the graphitization of the diamond grains. After verification, the accuracy of the simulation model for calculating the protrusion height of diamond grains was controlled within a range of ±15 μm. The results of this study provide a theoretical basis for the industrial application of MV-EDM to sharpening.

Wear characteristics of micro-structured CVD diamond grinding tools

It was an effective method to improve the machining performances that appropriate structured surfaces can be machined on the surface of grinding tools. However, the wear characteristics which also as an important evaluation of tool performance have so far not been conducted for the micro-structured grinding tools. In this paper, the wear characteristics of the micro-structured chemical vapor deposition diamond (CVD-D) grinding tools were investigated by comparing with the micro-structured coarse-grained diamond electroplated (CGDE) grinding tools and the micro-structured fine-grained diamond metal bond (FGDMB) grinding tools. The worn topography, composition change, grinding ratio and grinding force were analyzed. And the influences of the micro-structured parameters on wear behaviors of grinding tools were obtained. The results indicated that the micro-structured CVD-D grinding tools had better wear resistance. The CVD-D grinding tools with cross groove arrays had a higher grinding ratio and lower grinding force than that with inclined groove arrays. And the grooves with narrower widths were more favorable to grinding performance. Different from the micro-structured CGDE and FGDMB tools, the wear form of the micro-structured CVD-D grinding tool was the coating shed at the edge of the micro-structure, while the graphitization wear was not observed.

Fabrication and grinding performance of CVD diamond abrasive tool

The chemical vapor deposition (CVD) method has become a new choice for the fabrication of diamond grinding tools with excellent wear resistance. Different diamond abrasive particles were deposited on the lapping and sandblasting pretreated silicon nitride ceramic substrate by hot filament chemical vapor deposition (HFCVD) method to fabricate CVD diamond abrasive tools. To analyze the influence of pretreatment methods on adhesion strength, the micromorphology, surface roughness, Raman stress, and Rockwell indentation of CVD diamond abrasive tools with different parameters were characterized. Meanwhile, grinding tests on cemented carbide wire drawing dies were carried out, and the grinding performance of different abrasive particles was evaluated. The results show that sandblasting pretreatment can increase the matrix surface roughness, accelerate the growth of diamond abrasive particles and improve the adhesion between the abrasive layer and substrate, and the CVD diamond grinding tool with sandblasting pretreatment substrate and coarse particle has the best dust removal ability and the longest grinding life. The cemented carbide grinding tests of the CVD diamond grinding tool and electroplated diamond grinding tool with the same particle size are processed and compared, it shows that the grinding life of the CVD diamond grinding tool is longer, and the surface roughness value of the workpiece is lower than that of the electroplated diamond grinding tool.

Modeling and experimental study on the grinding performance of precision diamond grinding tool with defined texture

Modeling and experimental study on the grinding performance of precision diamond grinding tool with defined texture

Wear-adaptive optimization of in-process conditioning parameters during face plunge grinding of PcBN

Polycrystalline cubic boron nitride is a very hard material. Machining of this material is performed by grinding with diamond tools. Due to its high hardness, grinding tools are subjected to severe microscopic and macroscopic tool wear. This wear leads to short tool life and results in high effort in conditioning the abrasive layer. Contrary to the usual conditioning of diamond grinding wheels with diamond dressing tools, this study investigates a conditioning process based entirely on the use of white corundum cup rolls. These conditioning tools allow the in-process face plunge conditioning of vitrified bond diamond grinding tools. The circumferential speed of the conditioning tool and the average grain diameter of the corundum are identified as the main factors influencing the topography of the generated grinding layer. To describe the performance of the conditioning process, a specific conditioning removal rate Q_{sd}^{prime } is derived. This parameter represents a cumulated variable that allows a comparison of different conditioning strategies. It is shown that an increase in Q_{sd}^{prime } significantly counteracts microscopic wear on the abrasive layer. Therefore, optimized process parameters enable the process of in-process conditioning to significantly reduce wear on the grinding tool without increasing the process time or the non-productive time.

Research on a novel fabricating method of diamond grinding tool with defined grain arrangement

Grain-arranged grinding tool refers to a kind of grinding tool in which the position of abrasive grains on grinding tool can be controlled artificially. In this paper, a new method for fabrication of grain-arranged grinding tool is proposed, which is to directly coat the mask material (UV ink) on the metal substrate, and then by combining laser ablation and grain electroplating technology, the grinding tool with orderly arrangement of abrasive grains can finally be obtained. For the proposed fabrication method, the fabrication process is introduced in detail, mainly including the relationship between laser ablation parameters and the ablated mask hole depth, and the relationship between mask hole aspect ratio and the morphology of the plated layer in the mask hole. It is found that for laser ablation of UV ink, the critical laser power to remove the UV ink is 1.79 W, and the critical ablation threshold is 0.269 J/cm2. When the used laser power is 5.4–21 W, the relationship between laser power and the ablated hole depth is basically linear. For mask hole electroplating process, it is found that the unevenness of the plated layer in the mask hole and the growth rate of the plating layer increase with the decrease of the mask hole aspect ratio. By using the proposed method, grain-arranged grinding tool with 6 mm diameter, 95 μm grain size, and 150 μm grain spacing has been successfully fabricated, and its processing performance has been preliminarily validated by machining experiments.

Analytical and experimental study on micro-grinding surface-generated mechanism of DD5 single-crystal superalloy using micro-diamond pencil grinding tool

Single-crystal superalloy is characterized by no grain boundary and widely used in the aviation and aerospace industry due to its high creep strength and high thermal fatigue resistance, especially applications in aero engine necessitate numerous micro-scale structures made of single-crystal superalloy material with high-dimensional accuracy and surface quality. Micro-grinding as one of micro-precision machining technology is capable to fabricate micro-parts and structures with high machining precision and quality. In this work, a series of diamond micro-pencil grinding tool (MPGT) with diameter ranged from about 100 to 800 μm are firstly prepared by hybrid processes. The surface-generated mechanism of micro-grinding process associated with effects of length ratio of rubbing, ploughing and chip forming were explored based on analytical and experimental investigations. In addition, a novel analytical force model for the DD5 material machined by MPGT is developed considering variable size effect under different length proportion, protrusion height distribution of MPGT and material mechanical properties, which can more accurately agree well with the measured results compared with the traditional micro-grinding force model. This study enabled an in-depth understanding of mechanical behaviour characteristics, surface formation and material removal mechanism under microscopic scale of single-crystal superalloy involved in micro-grinding.

Supporting Body Material for Ceramic Diamond Grinding Tools

The characteristics of abrasive tools (the type of grinding wheel, granulation of the super hard grain, type of structure, hardness, and the type of binder) contain information on the type of supporting body materials used (e.g., dural, ceramic, steel). In this work, diamond wheels were obtained on ceramic supporting bodies, containing a sintered mixture of white alumina 99A granulation F320, green silicon carbide 99A granulation F320, and binder Ba23 bis, together with modifiers. The mechanical properties (hardness, bending strength) of ceramic supporting bodies were tested. The structure of the phase boundary of the ceramic supporting body–abrasive grinding tool was analyzed on a BEC (backscattered electron composition) image by using SEM (Scanning Electron Microscopy). It was found that the hardness of the supporting body was slightly lower (70–75 HRB) than the diamond wheels (76–81 HRB). The bending strength of the supporting bodies was high (85 ±2 MPa). The BEC image from the scanning microscope did not show a sharp transition between the ceramic supporting body and the grinding wheel. Preliminary operational tests showed significant improvement in grinding wheel efficiency in comparison to diamond tools with the same ceramic binder on a duralumin supporting body during machining of G30 sintered carbide bush.

On Material Removal Mechanism in High Speed Single Grit Scratch-Grinding of Cryo-Treated Al2024-T351 Aluminium Alloy

Feasibility of utilizing cryogenic technology to improve the shearability of Al2024-T351 alloy is experimentally investigated by carrying out a single grit scratch-grinding test. A single grit brazed diamond grinding tool is developed for the study. Al2024-T351 work specimens are treated with liquid nitrogen for 6 hours before the scratch test. Although there was no significant change in the tensile strength of the material, the surface experiences change in the microhardness. It helps in arresting the side flow and ploughing of the material during high speed scratch grinding. The scratched grooves on cryo-treated samples, compare to those of untreated specimens, shows signs of cleaner shear-cuts, superior finish and produces less grinding force during grinding