Diamond Abrasives Research Articles

Experimental evaluation of magnetic abrasive finishing process with diamond abrasive

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, in which, the work-piece is kept between two magnets and cutting force is controlled by the working gap and magnetic field. In this investigation, cylindrical surfaces of stainless steel were processed using MAF process to examine the percentage improvement in surface finish (PISF) and material removal rate (MRR). In order to complete the objective, four input process parameters (current, quantity of magnetic abrasives (MA), rotational speed, and percentage of diamond abrasives) were varied at different levels. Response surface methodology was adopted to investigate the significance of selected parameters. Further, mathematical models were proposed for response characteristics. Results exhibited that all the input parameters are significant for both the responses. The quantity of magnetic abrasives was found to have a major effect on PISF in comparison to the rotational speed. The minimum surface roughness value of Ra 17.7 nm was obtained.

Experimental evaluation of magnetic abrasive finishing process with diamond abrasive

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, in which, the work-piece is kept between two magnets and cutting force is controlled by the working gap and magnetic field. In this investigation, cylindrical surfaces of stainless steel were processed using MAF process to examine the percentage improvement in surface finish (PISF) and material removal rate (MRR). In order to complete the objective, four input process parameters (current, quantity of magnetic abrasives (MA), rotational speed, and percentage of diamond abrasives) were varied at different levels. Response surface methodology was adopted to investigate the significance of selected parameters. Further, mathematical models were proposed for response characteristics. Results exhibited that all the input parameters are significant for both the responses. The quantity of magnetic abrasives was found to have a major effect on PISF in comparison to the rotational speed. The minimum surface roughness value of Ra 17.7 nm was obtained.

The Effect of Different Post Space Surface Treatments on Push-out Bond Strength of Fiber Posts Adhesively Bonded to Root Canal Dentin

Aim: The purpose of this study was to analyze the effect of different post-space preparation and irrigation protocol on bond strength of resin cement to root canal dentin. Methods: Teeth were endodontically treated. After post-space preparation every sample was assigned to one of three groups. In each group different preparation and irrigation protocol was performed as follows: 0.9% saline solution (Group A), 37% phosphoric acid etch which was activated with an ultrasonic tip then rinsed with 10 mL of 0.9% saline solution (Group B), and manipulated with abrasive diamond tapered stone with round end then rinsed with 10 mL of 0.9% saline solution for 10 seconds (Group C). Two parts (coronal and apical) of each sample were analyzed by push out test. Push out bond strength measurements were recorded. Results: For coronal part, group C showed the highest significant values followed by Group B followed by Group A. For apical part, group B showed the highest significant values followed by Group A followed by the Group C. For the total; Group B and C showed highest value compared to group A with insignificant difference between B and C. For comparison between Coronal and Apical; Apical section showed a significant lower value compared to Coronal section for all tested groups at p≤0.05. Conclusions: Phosphoric acid etch activated with an ultrasonic tip then rinsed with saline solution appeared to be the best mode of preparation and irrigation when self-etch bonding is used since the adhesion interface is made by a thick smear layer.

Research of the Cutting Possibility of Magnesium Alloys with Abrasive Diamond Wire Saw

Abstract Wire saw technology is a method that works great in industrial applications – it is a dominant method in the production of silicon wafers. But almost all kinds of brittle materials (ceramics, rocks, meteorite and minerals or wood) can be cut using wire saw. Question, this article will try to answer is whether this is also applicable to magnesion alloys? Article presents selected problems from an area of abrasive treatment of magnesium alloys. This includes effects of research, concerning possibilities of application of abrasive diamond wire in the process of cutting magnesium alloys AM60 and AZ91 as well as results concerning surface quality obtained after cutting with the abrasive diamond wire German Company HK Präzisionstechnik.

Microscopic wear study of the sintered diamond trepanning drill during machining alumina armor ceramics

High purity engineering ceramics have been increasingly used for constituting novel lightweight ceramic composite armors along with various FRP materials. In the assembly process of ceramic composite armors, a large number of hole processing is required. Usually, diamond trepanning drills are preferentially adopted for machining relatively large holes of engineering ceramics. However, during drilling high purity armor engineering ceramics, the diamond tools are usually worn considerably due to their high dynamic compression strength and high hardness. In this study, taking the high purity alumina armor ceramics (99 wt% Al2O3) as machining object, the comprehensive wear features of the sintered diamond trepanning drill have been intensively studied through SEM examinations, including the microscopic wear morphologies of diamond grains and matrix binding agent, the diamond abrasion mechanism, the wear disfigurations of the drill labial surface and the drill slipping mechanism. According to the discussed results, the wear process of the diamond grains at the matrix labial surface can be divided into three stages: intact crystal, slight wear and severe wear stages. The quicksand phenomenon occurrence around the diamond grains is the typical feature of the matrix binding agent wear. The normal grinding of the drill can be interrupted by the severe inner-trumpet-shape wear and the cutting-groove wear of the drill labial surface. In most situations, only the slight inner-trumpet-shape wear occurs for the drill, which does not affect the normal drilling operation. The drill slipping is mainly attributed to the fact that most exposed diamond grains at the drill labial surface have been rubbed down into a polished planar shape and totally blunted. The results achieved in this study can provide helpful references for the performance improvement design of the sintered diamond trepanning drill.

Realization of high efficiency and low damage machining of anisotropic KDP crystal by grinding

Potassium dihydrogen phosphate (KDP) is a non-linear material used in various opto-electronic applications including Q-switches, high-speed photography shutters, frequency harmonic generation lens and Pockels cells in the Inertial Confinement Fusion (ICF) devices. KDP belongs to the most difficult-to-cut material, due to its delicate and unique characteristics including the combination of softness with brittleness, anisotropic performances, tendency for deliquescence and sensitivity to temperature change. Single point diamond turning (SPDT) is considered to be the ideal method for machining KDP components. However, the process efficiency is rather low and often accompanied with severe tool wear issues. This paper studies the feasibility using grinding method to remove the surface material of KDP components with high process efficiency and low damage, fulfilling the task of re-aligning the surface orientation to the crystalline axis. The grinding tests were carried out on a common CNC grinder, using resin bonded diamond grinding wheel, whilst the diamond abrasives are coated with Ni-P alloy. The direction of precision grinding was determined by studying the anisotropy of KDP, including its elastic modulus E, Vickers hardness HV and fracture toughness KIC, to reduce the influence of material anisotropy on machining quality. The grinding process parameters were preliminarily determined based on the experimental results investigating the effects of peripheral speed of the grinding wheel, worktable feed rate and grinding depth on the ground surface roughness. The surface defects, surface morphology and sub-surface damage under different process parameters were investigated. Surface roughness Ra ≤ 0.3 μm and sub-surface damage depth SSD ≤ 6 μm were obtained. The machining efficiency can be improved by nearly ten times using the proposed precision grinding method, producing nearly the same surface quality (Ra ≤ 0.2 μm, SSD ≤ 6 μm) as that in the axis fixing phase in SPDT.

Fabrication of fixed polishing tool by knitting diamond/CNT fiber threads on cloth

In this paper, a novel polishing tool has been prepared by knitting diamond/CNT fiber threads on cloth. Diamond particles are adhered to the surface of CNT fibers which are immersed in the diamond solution. Heat treatment is used to fix diamond abrasives on the CNT fibers, and the corresponding experimental parameters are discussed. Then the diamond/CNT fiber threads are knitted on cloth by method of cross-stitch and the processing performance of polishing tool is evaluated. Results reveal that the concentration of diamond solution and immersing time have great effect on the amount and uniformity of diamond on the surface of the fiber. And the effect of adhesion get an ideal result when the concentration of diamond is 0.5 wt% and the immersing time is 5 min. Diamond particles are bond with carbon nanotube fibers under heat treatment conditions, and the effect on the tensile strength of the fiber is obvious. Proper heat treatment parameters make it reach to 168.74 Mpa compared with the original's 83.35 Mpa, increased by 102.4%. The fixed diamond abrasives polishing tool is used to process agalmatolite, whose performance is compared with polishing tool made of pristine carbon nanotube fibers, and results indicate that the former has certain removal effect, and its wear resistance is better than the latter.

The effects of deposition parameters on the grain morphology and wear mechanism of monolayer diamond grinding tools fabricated by hot filament CVD method

The hot filament chemical vapor deposition technique (HFCVD) is used to fabricate monolayer grinding tools with high quality diamond abrasive grains. The high pressure and high temperature (HPHT) diamond seeds are distributed on SiC substrate randomly by a spin coater machine. Then epitaxial growth of CVD diamonds is conducted on both seeds and substrate simultaneously. The heteroepitaxial diamond film on substrate serves as a bonding layer to anchor the seeds, and the homoepitaxial growth of the seeds leads to changes in their morphology, purity, as well as mechanical properties. The grown seeds can be used as abrasive grains of the grinding tools. In this work, a systematic study is presented into the effects of deposition parameters (substrate temperature, carbon concentration, reactive pressure, bias current) on the growth behavior of diamond seeds. As a result, it is found that the well-faceted single crystal diamond (SCD) grains can be grown at 800 °C, 4.5 KPa, carbon concentration of 1.5% and bias current of 2 A. Besides, the increase of temperature and decrease of pressure allow the changes from SCD grains to microcrystalline diamond (MCD) clusters or further, to nanocrystalline diamond (NCD) clusters, while the high bias current and carbon concentration promote the growth of dislocated planes and secondary nucleation. Moreover, it is found that the protrusion of the diamond abrasives can be controlled by the difference in growth rates between seeds and diamond bonding films under various conditions. Finally, the wear resistance of diamond grains is tested. Results show that the wear of SCD grains is dominated by a high rate of wear flat and few fractures, and the wear of MCD grains exhibits less wear flat but more fractures, while the NCD grains exhibit the worst wear resistance in terms of both fracture and wear flat.

Electrochemical Characterization of a Nickel-Phosphorus Coating on Diamond Grits

Abstract Machining tools electroplated with coated diamond abrasives are widely used because of their high wear resistance. However, the inconsistent quality caused by coating failure has hindered tools’ performances and service lives. In the present work, experimental investigation through electrochemical approach was conducted on a coating electrolessly plated on diamond grits. A newly designed working electrode with nickel-phosphorus alloy coating was fabricated. Subsequently, immersion test, potentiodynamic polarization, and linear polarization resistance (LPR) and open circuit potential (OCP) monitoring were performed on this electrode, in order to reveal insight from the failure mechanisms of coatings. Morphological characterization was carried out before and after both the potentiodynamic polarization experiments and immersion test. The results showed that, in a low-concentration (60 g/L nickel sulfamate) bath, the coating cracked and stripped off because of the current assisted breakthrough of pinholes, while the coating has less damage in the high-concentration (300 g/L nickel sulfamate) bath because of an extra passivation stage at lower potential (−0.30 V versus OCP). The increase in OCP and decrease in corrosion rate over time indicated the continuous coating cracking and exposure of the nobler diamond substrate. LPR and OCP monitoring is an effective approach to evaluate the coating durability before the coated diamond grits are actually used in wire saw manufacturing. The electrochemical characterization methods used in this work can be applied to other core-shell systems with metal coatings and particulate substrates.

Scribing Characteristics of Glass Plate with Ground PCD Scribing Wheel

Polycrystalline diamond (PCD) tools are widely used for cutting tools because PCD has no crystal orientation and is an isotropic material, it is low in cost, and it is easily machined by electric discharge machining. PCD is sintered from diamond abrasives with an alloy metal, such as cobalt, and it is difficult to reduce the surface roughness and the edge accuracy compared with single crystal diamond. In this study, high efficiency and high precision machining of the PCD wheel were investigated. In the experiments, PCD wheels were ground with a diamond wheel, and the effects of the grinding direction and the load on the tool preciseness and the scribing performance were examined.

Current Advances in the Development of Abrasive Tools and Investigation of Diamond Abrasive Machining Processes (Materials Science Approach). Review

The paper reviews the latest advances in the development of abrasive tools and investigation of diamond abrasive machining processes. The review demonstrates the necessity of taking into account the interaction between abrasive and workpiece materials as well as the influence of elements of a workpiece material on wear of abrasive grains; also, it shows the importance of sorting diamond grains by shape, especially within a wide range of their strength. Special features of application of CVD diamonds and the methods for changing the diamond–bond interface zone in order to improve grain retention are discussed.

The influence of crystallographic orientation on wear characteristics during single abrasive diamond grit scratching on sapphire

PurposeThe wear of an abrasive single-crystal diamond (SCD) grit affects the machining quality of the sapphire wafer. This paper aims to investigate the influence of crystallographic orientation on the wear characteristics of SCD grit scratching on sapphire.Design/methodology/approachThe wear characteristics of two SCD grits (SCD100 and SCD111) with different crystallographic orientations were systematically investigated. The wear mechanism involved in the scratching process was explored. The wear morphology, scratching forces and friction coefficient during the scratching process were measured and analyzed.FindingsThe experiment results show that the wear progress of the two SCD grits is obviously different. The wear resistance of SCD111 grit is greater than that of SCD100 grit in normal wear stage. However, the SCD100 grit could remove more sapphire material than SCD111 grit. The SCD grits mainly sustain extrusion stress and shear stress during scratching on sapphire. The crystallographic orientation of SCD grits plays a significant role in the wear progress during scratching on sapphire.Originality/valueThe results of the experimental studies could provide a theoretical foundation for improving the fabrication of abrasive diamond tools.

Local Strain Distribution and Microstructure of Grinding-Induced Damage Layers in SiC Wafer

The high-angular-resolution electron backscatter diffraction (HR-EBSD) technique has been utilized to evaluate the elastic strain distribution of grinding-induced damage layers in silicon carbide wafers. HR-EBSD analysis, along with transmission electron microscopy observation, revealed that the damage layers formed beneath the wafer surface when the surface was ground by diamond abrasives; the layers were classified hierarchically based on the distribution of elastic strain and lattice defects. In particular, very large elastic strain formed in a defective region of roughly 0.6 μm in thickness, just beneath the ground wafer surface, where lattice defects such as dislocations, stacking faults, and microcracks were introduced inhomogeneously by abrasive interaction and related plastic deformation and fracture. Based on this inhomogeneity, the defective region was itself classified into two types: one, a highly defective region with very large, complicated strain and high defect density; and the other, a basal plane dislocation (BPD)-glide region, with small strain and few BPDs or stacking faults. Beneath the defective region, a strain gradient region of roughly 1.8 μm in thickness, which was unambiguously identified by HR-EBSD strain analysis alone, revealed a monotonic gradient in the dominant compressive strain component, with no grinding-induced defects. Overall, HR-EBSD analysis revealed a nanometer-scale, hierarchical elastic strain distribution in the grinding-induced damage layers.

Wear of diamond in scribing of multi-crystalline silicon

A practical challenge in slicing of low-cost multi-crystalline silicon (mc-Si) wafers by the fixed abrasive diamond wire sawing process is increased wire consumption due to greater wear of the diamond compared to slicing of the more expensive mono-crystalline silicon (mono-Si) wafers. In this paper, we present the results of scribing of mc-Si and mono-Si materials with two conical tip diamond indenters of the same geometry to understand the possible reasons for increased diamond wear in cutting of multi-crystalline silicon. Specifically, the scribing forces and the diamond indenter wear produced in scribing of the two silicon materials are analyzed. The results show that the forces generated in scribing of mc-Si are higher than in scribing of mono-Si. The higher forces in scribing of mc-Si are consistent with the corresponding higher tip radius of curvature (due to wear) of the diamond indenter compared to the tip radius produced in scribing of mono-Si. Scanning electron microscopy and confocal microscopy of the diamond indenters show that wear is primarily due to physical micro-fracture and blunting of the diamond. Raman spectroscopy shows evidence of stress-induced phase transformation of the diamond and the formation of compressive residual stress in the diamond. Plausible physical reasons, including the role of material inhomogeneity in mc-Si, for the wear of diamond during scribing are given.

Investigation of the progressive wear of individual diamond grains in wire used to cut monocrystalline silicon

The wear of diamond-coated wire is an important cost driver in the multi-wire sawing of silicon-based photovoltaics. Understanding the different forms of diamond wire wear could help the solar energy industry to be more competitive by reducing wafer costs. In this study, an innovative method was applied to investigate the wear of diamond wires: several diamond grains in a diamond wire loop were tracked during the slicing of monocrystalline silicon. The grains attached to the wire were analyzed by scanning electron microscopy and focus variation microscopy. Based on the observed non-uniformity of wear on the perimeter of the cross-section of the wire, the rotation of the wire on its longitudinal axis was investigated. A new method that promotes wire rotation during cutting was successfully applied. The form and progression of the wear were also investigated by tracking single grains during the cutting process. Observations show the occurrence of nickel layer removal/deformation, micro-chipping of the diamond grains, abrasion wear, and sporadic grain pullout.

Etching Shapes the Topography of Silicon Wafers: Lattice-Strain Enhanced Chemical Reactivity of Silicon for Efficient Solar Cells

Multiwire sawing of silicon (Si) bricks is the state-of-the-art technology to produce multicrystalline Si solar wafers. The massive indentation of the abrasive Si carbide or diamond particles used leads to a heavily mechanically damaged layer on the wafer surface. Etching the surface layer using typical HF–HNO3–H2SiF6 acid mixtures reveals an unevenly distributed etch attack with etch rates several times higher than known for bulk Si etching. The present study follows the hypothesis that lattice strain, introduced by the sawing process, leads to an increase of the etch rate and determines the topography of the etched wafer, the so-called texture. Scratches were introduced into single crystalline Si surfaces in model experiments, and the magnitude and local distribution of lattice strain were extracted from confocal Raman microscopy measurements. The essential parameter used to describe the local reactivity of Si is the local etch rate, which was derived by confocal microscopy from the local height before ...

Magneto-Abrasive Materials

Magneto-abrasive materials, obtained via the joint mechanical activation of magnetic (metal) and abrasive (diamond, silicon carbide) components in a high-energy planetary-type ball mill, are studied by means of XRD phase analysis and optical and scanning-electron microscopy. It is shown that a metallomatrix structure forms in an Fe/diamond system after only 10 min of mechanical activation. Diamond particles are ground from 40–50 μm to 0.5–3 μm and distributed over the volume of the iron matrix. Study of the abrasive properties of Fe/silicon carbide composite applied to zirconium alloy shows that an Fe/SiC composite obtained via 10 min of mechanical activation ensures the greatest reduction in the weight of the material and the lowest level of roughness.

The wear mechanisms of reaction bonded silicon carbide under abrasive polishing and slurry jet impact conditions

A study of the wear mechanism on a reaction bonded silicon carbide (RB-SiC) subjected to fixed abrasive polishing and loose abrasive waterjet (AWJ) impact conditions is presented. It is found that the wear of the material is characterised by different mechanisms in its silicon and silicon carbide constituents. The surface polished by diamond abrasives appears with brittle fractures on the silicon carbide phase, while the silicon phase is found to be plastically deformed and embedded onto the surface of the fractured silicon carbide. Sub-micrometer surface finish can be obtained by polishing using silicon carbide abrasives, and the process is initiated through the penetration of abrasive tips into the softer silicon matrix. Since the progressive wear flattens the tips of abrasives, the penetration depth of abrasives into the material gradually decreases. When the penetration depth is below a critical value, ductile material removal mode becomes dominant in the removal process. When abrasives that are softer than the silicon carbide grains are sufficiently introduced onto the material surface by a slurry jet, wear can occur even at a pressure below the critical value for phase transformation of the silicon constituent. Wear takes place mainly through weakening the Si bond by erosion and wedging, which eventually releases the SiC grain from the material structure. It is feasible to use a relatively low-pressure alumina slurry jet to machine RB-SiC without causing any surface damage and the processed surface quality depends mainly on the material structure.

ANN-NSGA-II dual approach for modeling and optimization in abrasive mixed electro discharge diamond grinding of Monel K-500

Hybrid machining processes (HMPs) have attracted the attention of investigators from both academia and industry due to their enhanced process performance and capabilities while machining so-called difficult-to-cut materials. In this paper, the dual approach of Artificial Neural Network (ANN) and Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) was used to model and optimize a new HMP called as Abrasive Mixed Electro Discharge Diamond Grinding (AMEDDG). Due to complex nature of AMEDDG process, the choice of an appropriate coalition of input factors is an effortful job for machinist. The central composite rotatable design was used to plan the experiments and ANN model was established to observe the effect of input machining parameters viz. Wheel speed, powder concentration, pulse current, and pulse-on-time on material removal rate (MRR) and average surface roughness (Ra). The established ANN model was found to be capable of forecasting the output responses within tolerable limits for the chosen set of machining parameters. An ANN-NSGA-II based dual approach was applied for multi-objective optimization of control factors in AMEDDG, and experimental validation directs that optimal data was in tolerable limits.

Novel Polishing Method of Cutting Edge Using AС Electric Field for Controlling Flank Wear

Polycrystalline cubic boron nitride (cBN), a super-hard material used for hard turning, has good compatibility with steel. However, because chipping occurs from already existing defects and worn out cutting edges, a cBN insert must be exchanged within a short cycle time. By reducing chipping and flank wear, one can reduce the tool costs related to cutting processes and reduce the number of times the insert has to be exchanged, leading to improved productivity. In this study, the authors hypothesize that chipping and flank wear during cutting reduced by polishing a tool edge finely, uniformly, and smoothly before cutting. An apparatus capable of polishing and smoothing a cutting tool edge uniformly is developed. In the free-abrasive control method, application of an AC electric field during polishing is applied to suppress the scattering of abrasives from the tool cutting edge. Results show that scratches created by grinding are nonexistent. Moreover, a smooth cutting edge is obtained after polishing treatment. The wear width of the polished cBN tool under a cutting speed of 50 m/min is half of that of the non-polished treatment tool. Furthermore, no chipping occurs with the polished cBN tool under any conditions. Additionally, results show that the same effect is obtained even when Silicon carbide (SiC) abrasives are used. The n value calculated using the Taylor tool life equation is almost identical in cases of both diamond and SiC abrasives.