Diamond Tool Research Articles

Cryogenic assisted femtosecond laser ablation of polycrystalline diamond

Polycrystalline diamond (PCD) tools have gained popularity in machining industry ascribed to superior surface quality and durability at elevated temperature and abrasive forces. A major obstacle for high-speed PCD machining is the excessive heat production that transcend the heat dissipation capacity, resulting in reduced tool life and performance. Surface microstructures on PCD tools can improve thermal performance by increasing the heat transfer area and reducing the thermal contact resistance, therefore enhancement in durability and operation. Femtosecond laser processing is a non-contact, high precision and low thermal effect technique for creating superior quality microstructures. This study investigates the effects of cryogenic-assisted femtosecond laser processing in improvement of diamond microstructures quality. Initially the effects of different laser settings on the performance of the process were investigated by conducting single-factor experiments at ambient conditions. Later, the effects of cryogenic assistance on diamond irradiation, surface quality and chemical changes were investigated utilizing laser confocal scanning microscopy (LCSM), scanning electron microscopy (SEM) and Raman spectroscopy. Cryogenic laser ablation had no effect on the diamond removal rate, on contrary improved the surface quality by reducing the surface roughness and graphite disorderliness. This study reports superior surface quality finish for cryogenic assisted laser ablation than ambient conditions therefore it is recommended to irradiate PCD at low temperatures.

Study on the atomic removal behavior and damage formation mechanism of nano cutting copper–nickel alloy with diamond tool

The effects of tool rake angle and cutting depth on cutting temperature, cutting force, friction coefficient of rake tool face, atomic accumulation of chip flow and removal, surface quality, sub-surface damage layer thickness, atomic stress, and dislocation evolution were studied by molecular dynamics simulations. The results showed that the cutting temperature was concentrated on the chip, and the chip was easy to flow out with the increase of the tool rake angle, which weakens the extrusion and shearing action of the workpiece, resulting in the gradual reduction of tangential force. The tool rake angle of 10° is beneficial to improve the surface/subsurface quality of the workpiece. The minimum root-mean-square roughness obtained was 0.73 Å. The atomic stress of the workpiece was mainly concentrated around the area of interaction with the tool, and the atoms on the finished surface underwent elastic recovery, so the atomic stress was not significant. The 1/6<112> (Shockley) dislocation density had always been in the leading position, and 1/6<112> (Shockley) dislocation was continuously synthesized and decomposed during the nano-cutting process. With the increase of cutting depth, the number of atoms removed increases rapidly, and the width of chip side flow increases, but the symmetry is weakened. The contour line map even shows deep wave valleys caused by the absence of atoms, which increases the surface roughness. Moreover, the area and depth of the atomic stress distribution in the subsurface layer increase, and the number of amorphous atoms and dislocation density increase.

Wear performance of diamond tools during sawing with reciprocating swing frame saw

The kinematics analysis of the reciprocating swing frame sawing machine was carried out, and the theoretical cutting depth and scratching mechanics models of diamond grain were established. Furthermore, sawing test and cutting force test were fulfilled on a reciprocating swing frame saw prototype to verify the interaction characteristics between segment and stone and explore the wear characteristics of diamond tools. It was indicated from the results that the segments in the synchronous contact region initially participated in sawing once at a reversal point in 1 cycle, and then scratched and removed the accumulated stone debris before cutting into the stone and after separating from the stone. The macroscopic crushed and pull-out diamond grains on segment surface in the synchronous contact region were relatively common, while the ratio of the failed diamonds in the sequential contact region decreased significantly and changed positively with the theoretical sawing depth. The diamond exposure in the synchronous contact region was associated with the scratching length of the diamond at the corresponding side, while the diamond exposure in the sequential contact region was relevant to its theoretical sawing depth in the corresponding stroke. Trailing tails shaped like those generated in circular sawing were developed on the side of diamond grain with less wear on the matrix bond in sawing process with reciprocating swing frame saw. The radial residual height of the segments in the synchronous contact region was significantly lower than that in the sequential contact region.

Fabrication of polycrystalline diamond micro-milling cutter with different grain sizes by picosecond laser

Polycrystalline diamond (PCD) is an excellent material for machining micro-tools due to its high hardness and wear resistance. However, the diameter of micro-milling tools is generally required to be less than 500 μm. When preparing micro-milling tools with a large aspect ratio, the processing load introduced by traditional grinding methods is easy to cause tool fracture. Therefore, a composite structure of carbide tool holder and diamond tool head is proposed in this paper. A technique of picosecond laser machining PCD micro-milling tool was studied, and the overall manufacturing process of tool blank preparation, nanosecond laser roughing and picosecond laser finishing was formed. A two-dimensional ablation mathematical model for tangential machining of PCD with a multi-pulse picosecond laser was established, and experiments verified the reliability of the mathematical model. In addition, the effects of picosecond laser pulse pitch, pulse energy, and track spacing on the surface quality of PCD materials with different particle sizes and cutting edge radius were studied by orthogonal experiments. The results showed that after picosecond laser processing, the surface roughness (Sa) of PCD with a particle size of 2 μm was the best, which can reach 0.33 μm, and the cutting edge radius of PCD micro-milling tool with a particle size of 25 μm was the smallest, which can get 1.67 μm. Using the optimized picosecond laser parameters, the high-sharpness single-edge micro-milling cutters with different particle sizes PCD with a diameter of 100 μm, aspect ratio greater than 3, and a cutting edge radius less than 3 μm were successfully fabricated.

Effect of Fe: Cu ratio on microstructure and mechanical properties of Fe-Co-Cu-based diamond tools

Co-based diamond tools are widely appreciated for their exceptional mechanical properties and good holding ability for diamonds. However, the reliance on cobalt (Co) poses challenges due to its high cost and scarcity as a strategic resource. A potential alternative is the Fe–Co–Cu alloy, emerging as a promising substitute for Co matrix alloys. In this work, hot-press sintering was utilized to create pure matrix and diamond tools utilizing Fe–Co–Cu pre-alloyed powders of varying compositions as raw materials without the use of any sintering additives. The investigation explores the influence of different Fe: Cu ratios on the mechanical properties of diamond tools produced from Fe–Co–Cu alloys, focusing on the diamond holding force, microstructure, and phase structure evolution. Results indicate that at a Co content of 15 wt% and Fe: Cu ratios ranging from 7.5:1 to 1:7.5, the Fe–Co–Cu alloy's phase structure primarily comprises α-Fe and a Cu-rich phase. Co predominantly exists in α-Fe as a solid solution. As the Fe: Cu ratio decreases, the alloy's phase structure gradually transitions from α-Fe to a Cu-rich phase, accompanied by a progressive decline in both bending strength and hardness, while the densities gradually increase. The matrix's holding force on the diamond exhibits an increasing and then diminishing trend, peaking at the Fe: Cu ratio of 6:1. The Fe–Co–Cu alloy sintered by hot-pressing has a nearly equiaxed grain structure with no obvious texture.

Electrodeposition of nanocrystalline cobalt from sulfate baths containing butynediol ethoxylate

Cobalt electrodeposit is a potential ideal matrix for precision diamond tools. In this work, cobalt electrodeposition was conducted in sulfate baths and the effects of butynediol ethoxylate (BEO) on the surface morphology, crystal structure, surface roughness and microhardness of cobalt deposits were investigated. Experimental results revealed that BEO had a strong inhibitory effect on the cobalt deposition process due to its high adsorption ability on cobalt; the addition of BEO favored the formation of smooth deposits of hexagonal close packed structure with [0002] preferred orientation, whose morphology was characterized by tiny granular structures, but it had trivial effects on their microhardness and average crystallite size. The changes in the properties of cobalt deposits could be related to the adsorption of BEO on (0002) plane of cobalt crystals, since the adsorption energy of BEO on this plane is much lower than that on other planes according to the results of molecular dynamics simulation.

Effect of PCD tool wear on surface morphology and material removal mechanisms in the micro-drilling of Cf/SiC composites: Experiment and simulation

This study investigates the polycrystalline diamond (PCD) tool's wear mechanism and the effect of tool wear on hole morphology in the micro-drilling of Cf/SiC composites. A 2D woven material model and tool wear model are created for the drilling simulation. The findings indicate that the wear mechanisms of the tools are mainly abrasive and adhesive. As the tool is worn, the quality of the hole entrance/exit and the shape accuracy deteriorate, and the surface roughness of the hole wall increases. Furthermore, a blunt cutting-edge radius shifts material removal from a shear effect to a compressive effect, transitioning from micro-brittle to macro-brittle removal. Notably, the simulation results approximately agree with the experimental results.

Simultaneous high-speed cutting and high-feed milling: An investigation on surface integrity

In this article, the potential of high-speed machining with an inverse cutting ratio b/h < 1 (uncut width of chip b to uncut chip thickness h) is presented based on the evaluation of surface integrity. If the machining is realized with a low cutting ratio many process quantities and chip formation mechanisms are fundamentally changed. As a result, the cutting process is stabilized through reduced feed forces and improved chip removal conditions. For the investigations, face-milling trials were carried out on an aluminum alloy (EN AC-42100) under conventional and high cutting speeds with variation of the feed per tooth and the use of cemented carbide and polycrystalline diamond tools. It is shown that when both machining strategies are combined, there is no further reduction in force components or improvement in surface topography. When the feed per tooth is increased at high cutting speeds, there is a linear increase in force components but surface roughness remain almost unchanged. After an initial increase in surface residual stresses, increasing the cutting speed leads mainly to compressive surface residual stresses. Overall, the surface integrity is influenced by the choice of cutting material and the micro-geometry of the cutting edge radius.

Effect of cutting speed on the surface integrity of single point diamond turned (100)Ge

The surface integrity of single crystal (100)Ge machined by on-axis single point diamond turning was investigated. The specimen was machined with a -25◦ rake angle single crystal diamond tool, with a depth of cut of 10 μm and a feedrate of 4 μm/rev. Six circular bands were machined on the specimen at different cutting speeds, ranging from 0.2 m/s to 10 m/s, while keeping all other machining and geometrical parameters constant. The surface topography was measured by atomic force microscopy and the near surface lattice disorder was investigated by Raman spectroscopy. The cutting and thrust forces were measured during machining, and their frequency domain was analyzed. Machining resulted in four lobes with four-fold symmetry, with differing amounts of surface fracture at each cutting speed. It was found that increasing the cutting speed generates surfaces with less or no brittle fracture for all cutting directions, causing some lobes to be undistinguishable. As the speed increased, the cutting and thrust force decreased monotonically. The frequency content of the force changed accordingly with the appearance of the surface, with a shift from 8 oscillations per revolution to 4 oscillations per revolution.

Characterization of Iron – Based Partial Pre - Alloyed Powders as Matrix Materials for Diamond Tools

Fe-Cu-Co is a structural component used in applications requiring both high strength and high hardness. A diamond cutting tool with iron -based (Fe -53%, Cu – 28%, Co -17%, P– 1% &amp; Ni -1%) pre-alloyed powders was prepared in the laboratory using powder metallurgy technique. Commercially available pure powders were combined to create the alloys, which were then roll compacted into bars and right away hot processed into fully dense alloy bars. Solid state sintering technique is used to manufacture composite material as it gives less defectives, more accurate than casting and excellent dimensional control. During sintering process metal powders are blended in ball milling and are compacted on hot press machine by applying heat and pressure simultaneously at different elevated temperatures. The sintered specimens are subjected to hardness, impact, density and porosity tests along with fractography study. From experimental observations it is found that material has high hardness than the steel, which can withstand mechanical vibrations, high impact strength and high toughness. According to experimental results it is most suitable for cutting applications, and there is a possibility to add diamond crystals in this tool, to strengthen hardness helping to cut the rocks.

Investigation of in-plane and out-of-plane micro-hole drilling on 2D-Cf/SiC composites

Carbon fiber-reinforced silicon carbide matrix composites (Cf/SiCs) are extensively utilized in the field of aviation and aerospace because of their superior mechanical qualities. However, it is difficult to machine high-quality small holes on them. To investigate the characteristics of micro-drilling on Cf/SiCs, the polycrystalline diamond (PCD) tool was used to machine holes on the in-plan and out-of-plan surfaces of Cf/SiC composites. The drilling force, the hole morphology and quality were explored. The mechanisms of material removal and tool wear were studied. The size effect during the micro-drilling process was also investigated. The outcomes showed that the out-of-plane drilling process yielded more thrust force and torque than the in-plane drilling process. The main forms of damage at the hole entrance and exit are tearing and burrs during in-plane drilling. The damage is mainly in the form of edge breaking caused by debonding and fracture of longitudinal fiber during out-of-plane drilling. The surface defects of the hole exit and entrance during out-of-plane drilling are fewer than those during in-plane drilling. The roundness errors of holes during in-plane drilling are fewer than those during out-of-plane drilling. Additionally, the surface roughness of the hole wall during in-plane drilling is less. Besides, brittle and ductile removal areas were observed at different fiber orientation angles (FOA). Furthermore, the rapid rise in specific cutting energy and the deterioration of surface quality when the feed rate is much smaller than the cutting edge proves the presence of the size effect. A new observation was that the abrasive wear of the flank face and chisel edge during out-of-plane drilling was more severe than that of in-plane drilling.

Investigation of milling performance and removal process mechanism of 3D SiCf/C-SiC composites using brazed diamond tools

The present paper evaluates the machinability of brazed diamond tools for milling 3D SiCf/C-SiC composites. Defined three milling modes of fiber orientation, transverse, longitudinal, and perpendicular, and surfaces, SA (transverse and longitudinal), SB (transverse and perpendicular), and SC (longitudinal and perpendicular), are chosen to reveal factors influencing milling force and surface integrity. Besides, the removal process mechanism is analyzed through high-speed cameras. The results show that combining fiber orientations influences milling force waveform, whereas surface quality is related to fiber orientation and damage types. The lower cutting speeds obtain better surface quality on SA surfaces, while superior surface quality on SB and SC surfaces is attained with higher cutting speeds. Dominant damage modes include direct fiber breakage and matrix fragmentation. Moreover, the removal process is sequentially matrix cracking and fiber/matrix debonding, fiber breakage, and ultimate failure. Toughening mechanisms of composites containing fiber bridging and fiber pullout are observed during milling.

Precision tailoring of laser beam propagation in a single crystalline diamond tool for in situ laser-assisted diamond turning.

The characteristics of laser beam propagation within a diamond tool critically influence the applied thermal softening capability of in situ laser-assisted diamond turning (In-LAT). In the present work, we perform optical geometric analysis, optical simulation and experimental validation to propose a novel diamond tool configuration for precisely tailoring laser beam propagation in In-LAT. First, the characteristics of laser beam propagation in the current In-LAT diamond tool are theoretically and experimentally explored. Second, according to the issues discovered in the current In-LAT diamond tool, an improved tool configuration based on the total internal reflection of a laser beam within the diamond tool is proposed, aiming for promoting refraction of the laser beam from the rake face of the diamond tool as well as eliminating the reflection of laser beam to tool holder. Finally, the optimization of laser beam incident position is carried out for achieving the superior profile and intensity of the emitted laser spot. Current work provides rational laser beam propagation for improving the thermal-softening capability of an In-LAT diamond tool.

A Comparative Study on the Wear Mechanisms of Uncoated and TiAlTaN-Coated Tools Used in Machining AMPCO® Alloy

A consistent evolution in materials developed for the industry and chip-start cutting processes has been acknowledged over the years. Cutting tool improvement through applying advanced coatings has proven very effective, enabling tool life (TL) extension while ensuring better surface quality. TiAlTaN coating enhances TL and surface quality in machining processes. However, only minimal research has been dedicated to comprehending the interaction between workpieces composed of Cu-Be and diamond tools. AMPCO®, a Cu-Be alloy, plays a crucial role in moulding inserts, offering high wear resistance and contributing to extended mould longevity and improved productivity. The main objective of this work is to assess, identify, and quantify tool wear (TW) mechanisms evaluation while machining AMPCO® with WC-Co uncoated tools and TiAlTaN-coated tools by physical vapour deposition (PVD). Evaluating tool performance while varying cutting length (Lcut) and feed rate (f) at three distinct levels and analysing the surface roughness (SR) produced in the machined surface were the primary purposes of this work. The results obtained with coated tools were distinct from those obtained with uncoated tools. While uncoated tools suffered from substrate abrasion and adhesion, the coated tools suffered mainly from delamination, followed by chipping. Furthermore, f and Lcut significantly influence the quality of the machined surface. TiAlTaN-coated tools performed significantly worse than uncoated tools, proving that the coating needs significant improvements to be considered as an alternative in milling Cu-Be alloys.

Material Removal Mechanism and Evolution of Subsurface Defects during Nanocutting of Monocrystalline Cu

Multigroup large-scalenanocutting models of monocrystalline Cu were established by molecular dynamics simulations to investigate the influence of cutting parameters on the material removal mechanism. The formation and distribution of subsurface defect structures were revealed, and the evolution behavior of the complete prismatic dislocation loop was analyzed in depth. It was demonstrated that the chips and machined surface of monocrystalline Cu were mainly formed under the coupling effect of shearing and extrusion forces. A diamond tool with a larger edge radius or a negative rake angle could produce a noticeable suppression on the chip formation. The corresponding relationship between the location of defect atoms and the distribution of von Mises stress was studied, which indicated that the shear stress would become larger at the subgrain boundaries, dislocation lines, and the amorphous atoms than that in their nearby regions. The complete prismatic dislocation loop was formed by cross-slip between two sets of stacking faults; meanwhile, the generated multiple Lomer–Cottrell locks hindered its movement and promoted the work-hardening phenomenon. These research results are of great theoretical value to enrich the nanocutting mechanism and technology of plastic materials.

Inhibition effect of covalent carbon nanosheets on mechanochemical wear of diamond

Diamond tools experience severe chemical wear when machining ferrous metals, which hinders their practical applications. In order to improve the wear resistance of diamond cutting tools, in the diamond-graphite strong covalent structure prepared by laser induced solid-phase diffusion, carbon nanosheets (CNS) can be obtained by electrochemical stripping of the graphite layer onto the diamond matrix, which provides a new way to improve the limitations of diamond tools in application. After 14,400 cycles of reciprocating sliding against the GCr15 ball at a normal load of 2–8 N, friction was reduced by 45.9 %–65.6 % with high durability. The oxygen content is reduced by an order of magnitude during this process, suggesting that the CNS can prevent oxidation behavior at the sliding interface. The bare diamond had a relative wear rate of 4.1–15.4 times that of the CNS. It showed competitive inhibition of mechanochemical wear. Our work provides a convenient and green method of preparing in-situ CNS covalently bonded on a diamond surface, extending the way for the prospect of carbon materials.

Fabrication of the curved Fresnel lens array on the spherical surface by 6-axis diamond ruling

The curved Fresnel lens array on the spherical surface owns exceptional optical performance and meets the growing demand for smart home and security alarm systems. However, the intricate three-dimensional microstructure of such optical component is typically considered impossible to be directly fabricated by diamond machining. In this paper, a novel 6-axis diamond ruling method is proposed to fabricate the complex optics utilizing a commercial 6-axis ultra-precision machine tool. The kinematic principle and tool path generation algorithm of this method are presented. A varying-angle sampling strategy is employed in the proposed algorithm to reduce the acceleration and following error in the rotation of the A-axis. Novel trial cutting processes are introduced to figure out the tool setting errors induced by visual inspection, which need to be compensated in the tool path. Based on the proposed tool path generation algorithm and cutting processes, this method enables the efficient processing of precise curved Fresnel lenses. There is no interference between the diamond tool and the curved microstructure in the 6-axis synchronized motions. Finally, the feasibility and superiority of this method are experimentally verified by analyzing the surface roughness and shape accuracy of the machined component. It can indeed generate high-quality curved Fresnel lenses on the spherical surface by the proposed 6-axis diamond ruling method.

Analysis of chip compression ratio in turning of polyoxymethylene copolymer

The turning process is influenced by a synergy of various parameters that affect the machining mechanisms and the resulting process efficiency. Among these factors, the evaluation of chip morphology is of paramount importance and can often be quantified by the chip compression ratio. This key figure serves as a quantitative measure of the overall plastic deformation and provides information about the energy expended during cutting and the friction behavior at the interface between the chip and the cutting tool. This research is specifically concerned with modeling and analyzing the chip compression ratio during dry turning of polyoxymethylene copolymer (POM-C) using a polycrystalline diamond (PCD) tool. The experimental setup comprised a face-centered, central compound test in which three main parameters — depth of cut, feed rate and cutting speed - were adjusted to each other. After conducting the turning experiments and collecting the measurement data, a second-order mathematical model was formulated to establish the relationship between the turning parameters and the chip compression ratio. Statistical analysis of the results revealed notable main effects of depth of cut and feed rate, a quadratic effect of depth of cut and an interaction effect between feed rate and cutting speed, all of which have a significant effect on the change in chip compression ratio.

Dynamic simulation of powder spreading processes toward the fabrication of metal-matrix diamond composites in selective laser melting

A novel method for the integrated production of structural and functional metal-matrix diamond composites is provided by selective laser melting (SLM) in the field of diamond tools. However, the uneven distribution of diamond particles and loose packing density in the powder bed can easily result in poor performance of diamond tools. In this work, a discrete element method model of diamond/CuSn composite powders is developed to simulate blade-spreading processes. It investigates how powder bed quality and particle dynamics are affected by diamond powder physical properties and powder spreading process parameters. The findings reveal that coarse diamond particles exhibit strong force chains at low velocities, whereas contact force chains are weak for fine CuSn particles at high velocities. It shows that diamond particles with irregular shapes have poor diffusivity and spreadability due to the large friction and mechanical locking forces, which causes diamond particles segregation. Therefore, the packing density and uniformity of the powder bed are both improved by reducing the volume fraction and particle size of diamond particles. In addition, the powder bed quality is improved by increasing the powder layer thickness and decreasing the translational speed of the blade, which weakens the shear expansion and jamming of diamond particles. The results have some significance for optimizing powder spreading processes toward the production of metal-matrix diamond composites in SLM.

Enhanced holding ability between resin and silanization modified diamonds through sintering Si[sbnd]N bond formation at low temperature

Resin-bonded diamond tools often suffer from poor durability and short lifespan due to the agglomeration of abrasive diamonds and the poor holding ability between diamonds and resin, resulting in diamond detachment during the working process. Modifying the diamond surface is necessary to improve the dispersion of diamonds and the holding ability between diamond and resin. However, common metallic modification methods can cause fine-grained diamonds (FGDs) to agglomerate, and metal plating cannot form a chemical bond with resin at low temperatures for preparing resin-bonded diamond tools. A practical non-metallic method for modifying diamond surfaces was proposed to address these issues, utilizing a silane coupling agent to enhance the binding forces between diamonds and binding agents. A uniform amorphous SiO2 film, with a thickness of 30–40 nm, was developed on FGDs with the hydrolysis and condensation reactions of tetraethylorthosilicate in a water and alcohol mixed solution. The SiO2 layer formed with the CO, CO, and C-O-Si chemical bonds can increase electrostatic repulsion between diamonds, overcoming diamond agglomeration. FGDs modified with SiO2 were combined with phenolic resin and pressed at 170 °C, forming SiN bonds between the resin and SiO2 film and improving the bonding force. Moreover, the SiN bonds can be produced at low temperatures, reducing the risk of diamond detachment during their operation. Hence, the lifespan of modified diamond wheel increase by 22 % than that of pristine diamond wheel. This study provides valuable guidance for developing high-performance, long-lasting, resin-bonded diamond tools.