Polycrystalline Diamond Tools Research Articles

Nanotwinned diamond cutting tool processed by femtosecond pulsed laser milling with trochoidal trajectory

Ultrahard nanotwinned diamond (nt-D) is an excellent diamond material with higher hardness, better fracture toughness and thermal stability than the commonly used single crystal diamond (SCD), thus it is considered as a promising tool material applied in ultra-precision cutting. However, extremely high hardness results in the fabrication of nt-D tool more difficult than SCD because of very low machining efficiency when using the conventional mechanical methods. Aiming to mass-produce of nt-D tool, the femtosecond pulsed laser milling technique was applied, and the related phase transition mechanism was explored during processing nt-D. Then, a trochoidal trajectory was proposed to acquire high forming accuracy and sharp edge in this study. It is found that the cubic diamond within nt-D was transformed into amorphization directly rather than graphitization under laser processing, which is attributed to the enhanced phase stability for nt-D. Furthermore, the nt-D surface integrity processed by laser was mainly restricted by diamond falling-off pits dewetting from grain boundary. Then, an optimized trochoidal trajectory method was proved to effectively decrease the depth of the falling-off pits and improve the surface integrity by the aid of laser pulse delay. Through the distribution calculation of pulse overlapping with the deduced theoretical equations and processing parameters optimization of galvanometer rotation, an nt-D cutting tool was successfully fabricated with smooth surface and sharp cutting edge. Finally, the wear mechanism, wear resistance and cutting performance of the as-fabricated nt-D tool were explored through cutting testing of hard polycrystalline MgF2. The results supported that nt-D tool exhibits better wear resistance and cutting performance than nanograined polycrystalline diamond (NPD) tool.

Modeling of Active Gap Capacitance Electrical Discharge Machining

Abstract Active gap capacitance electrical discharge machining (AGC-EDM) is a high-speed EDM method for machining polycrystalline diamond tools utilizing the active capacitive effect and powder mixing effect formed by the kerosene dielectric added with graphene particles. The capacitive effect increases the discharge energy and explosive force, which in turn influences the material removal efficiency; the powder-mixed effect changes the states of dielectric and forms a non-fixed gap discharge process. Take into account these two aspects, a new discharge mechanism of AGC-EDM is proposed to describe the discharge process. Capacitance characteristics and chain stacking process of graphene-kerosene dielectrics are verified by experimental results. The material removal rate, relative electrode wear, and surface roughness are discussed with the pulse duration, peak current, and graphene concentration to study the theories of the new EDM process.

Investigation into the Effect of Cutting Conditions in Turning on the Surface Properties of Filament Winding GFRP Pipe Rings

There are numerous engineering applications where Glass Fiber Reinforced Polymer (GFRP) composite tubes are utilized, such as desalination plants, power transmission systems, and paper mill, as well as marine, industries. Some type of machining is required for those various applications either for joining or fitting procedures. Machining of GFRP has certain difficulties that may damage the tube itself because of fiber delamination and pull out, as well as matrix deboning. Additionally, short machining tool life may be encountered while the formation of powder like chips maybe relatively hazardous. The present paper investigates the effect of process parameters for surface roughness of glass fiber-reinforced polymer composite pipes manufactured using the filament winding process. Experiments were conducted based on the high-speed turning Computer Numerical Control (CNC) machine using Poly-Crystalline Diamond (PCD) tool. The process parameters considered were cutting speed, feed, and depth of cut. Mathematical models for the surface roughness were developed based on the experimental results, and Analysis of Variance (ANOVA) has been performed with a confidence level of 95% for validation of the models.

Grinding techniques for fabricating micro-lens array mold made of cemented carbide (Polycrystalline diamond tools and mold surface roughness)

Grinding techniques for fabricating micro-lens array mold made of cemented carbide (Polycrystalline diamond tools and mold surface roughness)

Fabrication and evaluation of diamond thick film-Si3N4 brazed cutting tool by microwave plasma chemical vapor deposition method

• A novel CVD-diamond thick film-Si3N4 brazed WC-Co tool was proposed. Sandblasting-nanodiamond seeding pretreatment method was adopted for the diamond thick film deposition on Si3N4 substrates. • Tribological behaviors of the polished diamond film, diamond thin film and PCD were compared. • Cutting performances and wear mechanisms of CVD-diamond thick film-Si3N4 brazed WC-Co, diamond coated and PCD tools were investigated. Chemical vapor deposition (CVD) diamond thick film, due to its higher hardness and better wear resistance, is a potential competitor of the poly-crystalline diamond (PCD) when used as the brazed tool tip. Besides, compared with the thin diamond coated tool, the diamond thick film brazed tool does not have the risk of catastrophic coating delamination. However, due to the fragile characteristic of the free-standing diamond thick film, the conventional polishing is complicated and inefficient. In this study, a novel CVD-diamond thick film-Si 3 N 4 brazed WC-Co (i.e. DB) tool is proposed. The diamond thick film was deposited on the Si 3 N 4 substrate by microwave plasma CVD (MPCVD), using the optimized deposition parameters: microwave power = 3.5 kW, reactant pressure = 20 kPa and methane concentration = 10 %. Adopting the sandblasting and nanodiamond seeding pretreatment methods could improve the film surface smoothness and suppress the voids formation on the film-substrate interlayer, which are beneficial for the post polishing process. In addition, Si 3 N 4 as the supportive substrate could help to prevent the diamond film breaking from polishing. The polished CVD diamond thick film-Si 3 N 4 was laser cut to small tips and then brazed on the WC-Co cutter body. The cutting performance of DB tool was tested in dry turning hypereutectic Al-Si alloy, adopting the PCD and thin diamond coated WC-Co (i.e. DC) tools as comparisons. The cutting results suggest that DB tool outperformed the PCD and DC tools in term of service life and surpassed the DC tool in machining quality. Moreover, the novel tool in this study avoided some typical problems for the conventional diamond tools, such as the coating delamination for thin diamond coated tool and preferred wear of the binder for PCD tool. Noteworthy is that the worn DB tool still presents a rather sharp cutting edge, only some micro-columnar diamond crystals chipped from the flank face.

Experimental Investigation on CO2 Laser-Assisted Micro-Grinding Characteristics of Al2O3

Fabricating micro-scale features in ceramic materials, such as alumina (Al2O3), is challenging because of their high hardness and brittleness. Laser-assisted machining, in which a laser beam is a heat source for pre-softening the local area on a workpiece, is an effective hybrid method for machining ceramics. The study identified the effects of carbon dioxide (CO2) laser-assisted micro-grinding (LAMG) with a wire electrical discharge grinding polycrystalline diamond tool on Al2O3. Comprehensive investigations have been conducted on the effects of laser beam machining itself and the effect of machining parameters, such as laser beam power, axial depth of cut, and feed rate. The average grinding force was found to decrease by 46% in the thrust direction and 44% in the feed direction, and surface roughness decreased by 17% with LAMG. Moreover, machining at a higher feed rate was possible without tool fracture. The results indicate that the CO2 laser heating of Al2O3 has significant advantages over conventional methods regarding machinability and channel geometry. Finally, an improved LAMG process to prevent edge cracks by revising the machining conditions is proposed.

Lathe Parameters Optimization for UD-GFRP Composite Part Turning with PCD Tool by Taguchi Method

The aerospace and automobile sectors are widely utilized the polymer composites. The composite materials, like unidirectional glass fiber reinforced polymer (UD-GFRP), is difficult to machine due to its anisotropic that is non-homogeneous character and such material requires special cutting tools. The proposed work is going to examine the tool wear, quality of the surface and forces generated in the various stages of inputs given to the machining of unidirectional glass fiber reinforced polymer (UD-GFRP) composites. The assessment of the machining incorporates tool wear investigations, surface roughness investigations and quality of material by varying input parameters. The Taguchi optimization technique with experimental design of L9 orthogonal array employed. The parameters range identified by trail runs and observations of conducted machining utilized for optimization. The Turning process parameters of cutting velocity or speed, rate of tool movement or feed rate and cutting depth on composite part or depth of cut were considered. The other factors, like tool material i.e., Poly-Crystalline Diamond (PCD) tool, its cutting regime (dry), profile of cutting tool are considered as constant parameters. The responses, like tool wear, surface finish, and cutting force, were measured against various input parameters, while machining the composite (UD-GFRP) composite part. The objective of this research is to establish relationship among various operating parameters to achieve desired results. That is major focus of the work on the economic condition for getting better values based on setting of input parameters.

Optimization of cutting parameters of hybrid metal matrix composite AA6061/ZrB2 and ZrC during dry turning

The predominant aim of the research has been meant to evaluate cutting characteristic features of machining on AA6061/ZrB2-ZrC hybrid composite metal matrix with polycrystalline diamond tool. Though researchers understand, Taguchi would be used for dry turning operations to find the optimal cutting parameters. We have used the Taguchi L16 orthogonal array in the current investigation to evaluate the cutting characteristics. Through this work it’s analyzed that the optimal cutting as well as main cutting parameters actually affects the cutting performance. In order to understand the effectiveness of investigational optimization, confirmatory tests have been carried out hybrid composites fabrication composite has proved that it has better machining characterization. Hence, the fabricated composite can be recommended for applications especially hypersonic flight and rocket propulsion systems and because of the presence of hard ceramic material it is used commercially for the manufacture of cutting tools inserts.

Prediction and control of surface roughness for the milling of Al/SiC metal matrix composites based on neural networks

In recent years, there has been a significant increase in the utilization of Al/SiC particulate composite materials in engineering fields, and the demand for accurate machining of such composite materials has grown accordingly. In this paper, a feed-forward multi-layered artificial neural network (ANN) roughness prediction model, using the Levenberg-Marquardt backpropagation training algorithm, is proposed to investigate the mathematical relationship between cutting parameters and average surface roughness during milling Al/SiC particulate composite materials. Milling experiments were conducted on a computer numerical control (CNC) milling machine with polycrystalline diamond (PCD) tools to acquire data for training the ANN roughness prediction model. Four cutting parameters were considered in these experiments: cutting speed, depth of cut, feed rate, and volume fraction of SiC. These parameters were also used as inputs for the ANN roughness prediction model. The output of the model was the average surface roughness of the machined workpiece. A successfully trained ANN roughness prediction model could predict the corresponding average surface roughness based on given cutting parameters, with a 2.08% mean relative error. Moreover, a roughness control model that could accurately determine the corresponding cutting parameters for a specific desired roughness with a 2.91% mean relative error was developed based on the ANN roughness prediction model. Finally, a more reliable and readable analysis of the influence of each parameter on roughness or the interaction between different parameters was conducted with the help of the ANN prediction model.

Tool wear in laser ultrasonically combined turning of tungsten carbide with PCD tools

Tungsten carbides are typical difficult-to-cut materials due to their high hardness and brittleness, which cause severe tool wear and shorten tool life when being machined during conventional processing methods, leading to a loss of quality and accuracy of the machined parts. In this paper, a novel laser ultrasonically assisted turning technology for tungsten carbides was proposed, and the primary objective of this study was to investigate the behavior of polycrystalline diamond (PCD) tools when turning tungsten carbides with the application of ultrasonic vibration to tools and laser-induced heating to workpieces. To determine suitable parameters, thermal modeling of laser ultrasonically assisted turning of tungsten carbide was employed. Through contrast experiments carried out during conventional turning, ultrasonically elliptical vibration turning, laser-assisted turning, and laser ultrasonically combined turning of tungsten carbides with PCD tools, the tool wear characteristics and dominant wear mechanisms were investigated, and the relation between tool wear and surface quality of workpiece was determined by analyzing the effects of tool wear on the surface roughness values and the microtopography of the machined surface. A significant reduction in the cutting force and a substantial improvement in the tool life were obtained in laser ultrasonically combined turning of tungsten carbides with PCD tools when compared with conventional turning, ultrasonically elliptical vibration turning, and laser-assisted turning; therefore, lower surface roughness values and a good surface quality of the workpiece were obtained. During laser ultrasonically combined turning of tungsten carbides with PCD tools, the wear on the rake face was characterized by micro tipping and chipping, the flank face had shallow micro-grooves oriented along the cutting direction, and the dominant failure mechanisms of the PCD tools were the synergistic interaction of diffusion, oxidation, tipping, and chipping. With the increase in tool wear, the surface roughness values steadily increased in laser ultrasonically combined turning, and the cutting mode was changed from ductile mode turning to brittle mode turning, which resulted in many defects, including pits, voids, grooves, etc., on the machined surfaces.

Fabrication of Large Aspect Ratio PCD Micro-milling Tool with Pulsed Lasers and Grinding

Abstract Micro-milling tools greatly affect the surface quality and machining accuracy in the milling of the high-aspect-ratio microstructures. Polycrystalline diamond (PCD) micro-milling tools have superior performance than traditional carbide tools. However, the fabrication of the large aspect ratio PCD tool is a problem on account of its low stiffness and high hardness. Present study proposed a compound processing method, combining pulsed nanosecond laser, picosecond laser with precision grinding, to manufacture a designed large aspect ratio PCD micro-milling tool with 3/4 body efficiently and accurately. The nanosecond laser was used to remove the allowance quickly, then the grinding was employed to treat the rake face, and the picosecond laser was applied to make the cutting edges. The influence of the picosecond laser parameters on tool surface quality and cutting edge radius were investigated and an optimal PCD tool was fabricated. Then the machining performance of the fabricated PCD tool was compared with commercial cemented carbide tool in surface roughness, milling force and tool wear by micro-milling tests. Experimental results showed that the surface quality of the laser-treated PCD rake face is improved after grinding whose roughness is less than 1 μm. The surface morphology and radius of the picosecond laser-treated cutting edge are heavily dependent on the laser experiment conditions. The large aspect ratio PCD tool with a diameter of 0.5 mm, length-diameter ratio of 3 and cutting edge radius of 3.5 μm was obtained by using the optimal parameters. The micro-milling tests demonstrated that the fabricated PCD tool had predominant performance when milling the deep-narrow-grooves.

Research in the field of Polycrystalline Diamond Tools

The multitude of cutting materials already in existence increased further with the appearance ofpolycrystalline diamond (PCD) some 25 years ago. Ceramic show no chemical affinity to most machiningmaterials, but are very brittle. Natural diamond, the hardest known material, is very wear resistant, but alsosensitive to impacts and difficult to shape. The main advantage brought about by the development ofpolycrystalline diamond is the partial combination of the exceptional hardness of diamond with the toughness oftungsten carbide. This paper is presenting a series of the general considerations on cutting tools which have thecutting surface made of polycrystalline diamond. There are also presented some original results concluded by theauthor, based on experiments made with the tools mentioned before, which have different design values.

Environmental and resource aspects of substituting cemented carbide with polycrystalline diamond: The case of machining tools

Synthetic diamond competes with the conventional cemented carbide (WC–Co) tool material in some applications due to its extreme hardness. However, so far, these materials have not been compared from a life cycle perspective regarding their environmental and resource impacts. The aims of this study are i) to provide detailed life cycle assessment (LCA) results for industrial polycrystalline diamond (PCD) production from diamond grit produced via high-pressure high-temperature (HPHT) synthesis and ii) to conduct the first comparative LCA of PCD and WC-Co tools for the cases of wood working and titanium alloys machining. The results show that the main hotspot in HPHT synthesis of diamond grit, which is the main precursor to PCD, is the use of WC-Co in the high-pressure apparatus. In PCD tool production, the electricity input and the use of tungsten and molybdenum contribute the most to environmental and resource impacts. The environmental and resource impacts of the PCD tool production can be reduced with 53–83% if solar electricity and full WC-Co recycling is applied. The comparison shows high environmental and resource improvements when substituting WC-Co tools with PCD tools in wood working, but not in titanium alloys machining.

Cold Tribo-Nanolithography on Metallic Thin-Film Surfaces.

This paper demonstrates a modified tribo-nanolithgraphy (TNL), micro- to nanometer scale mechanical machining processes, on metallic thin film surfaces which have poor machinability in micro scale under several mN normal loads. TNL is one of the promising atomic force microscopy (AFM)-based lithography processes which is more effective fabrication technology, as compared to conventional photolithography due to its relatively simple processes, high resolution, short processing time, and low cost. We propose ultra-precision machining at sub-0 °C temperatures using a lab-made micro polycrystalline diamond (PCD) tool on a retrofitted piezo stage with a Peltier device. The workpiece, located on the stage, is cooled artificially, and a normal load of several mN is applied by a micro PCD tool for micro scale machining processes. The machining results indicated considerably different machinability when the work was performed at sub-0 °C, as opposed to the ambient surface temperature, due to the changed mechanical characteristics of surface by the forced cooling of the workpiece. Although the normal load, machining speed, and machining area remained constant, the width and depth of machined grooves are significantly increased at sub-0 °C temperature conditions. In addition, we analyzed the TNL characteristics when machining with the PCD tool in four different machining directions. The mechanical surface properties, surface topography, scanning electron microscope (SEM) images, chip formation and other physical properties are investigated for more discussions.

Design, optimization and manufacturing of polycrystalline diamond micro-end-mill for micro-milling of GH4169

Diamond micro mills are very suitable to process the nickel-based superalloy GH4169 because of its high stiffness and edge sharpness. The geometric parameters of micro-end-mills have a significant effect on the milling process. In order to determine the optimal tool geometric parameters, a micro-end-mill was designed and used to simulate the micro-milling of GH4169 with a three dimensional (3D) finite element method (FEM). Subsequently, micro-milling verification experiments were performed. In the simulation, the maximum tension stress of the tool (MTST), the range of cutting force fluctuation (RCFF), and the residual stress of the machined surface (RSMS) were defined as indicators of parameters optimization. The obtained optimal tool parameters were: rake angle of 0°, relief angle of 9°, and cutting-edge radius of 1–1.5 μm. Moreover, the above optimal parameters were used to manufacture a micro-end-mill of polycrystalline diamond (PCD) through the precision grinding method assisted by laser-induced graphitization. Cutting experiments using commercial and PCD tools demonstrated that the PCD micro-mill has better cutting performance than a commercial cemented carbide micro-mill.

Finite Element Analysis on Processing of PCD End-Mill Milling Copper

Polycrystalline diamond (PCD), is a tool material and widely used in nonferrous metal processing due to its excellent properties, such as high hardness, high wear resistance, high thermal conductivity and low friction coefficient. Considering the friction between the cutter and the workpiece, the heat generated by the elastic-plastic deformation and the heat transfer between the cutter and the workpiece. The finite element analysis software ABAQUS was used to study the effect of different processing parameters on the temperature field distribution and cutting force of the cutter, in the case of welded PCD double-edge end milling copper. The temperature distribution of cutting tools and the changing trend of cutting force with milling parameters was obtained. These technological parameters include the milling rotation speed n, the axial milling depth ap, and the feed rate f. The simulation results show that the tool temperature increases with the increase of milling depth, feed per revolution and rotation speed. However, the tool temperature has little effect on the tool life. Under the condition of satisfying the work-piece surface quality and machining efficiency, low speed, small milling depth and small feed should be selected as far as possible. Milling depth has a great influence on cutting force. When milling speed is about 2400 r/min, the axial milling depth is 0.3 mm, and the feed is 0.2 mm/r, which can obtain small milling force and lower tool temperature, and further extend the life of PCD tool.

Structural design and fabrication of polycrystalline diamond micro ball-end mill

Since cemented carbide has been used as a micro-lens array mold, its processing method and micro-tool is one of the research priorities. In order to achieve high-quality milling of cemented carbide micro-lens array, the design and fabrication of the 0.5-mm diameter polycrystalline diamond (PCD) micro ball-end mill were studied. Based on the space vector, the mathematical model of the plane cutting edge of the PCD tool is established. According to the three processing characteristics of milling, grinding, and milling grinding, the double-edged conical surface micro ball-end mill, spherical micro ball-end mill, and single-edged hemispherical micro ball-end mill were designed respectively. Based on the line-face contact model of the grinding wheel and the movement principle of the CNC tool grinder, the grinding principles and methods of the rake face and the flank face are proposed. The high precision grinding of PCD micro ball-end mills are realized. The micro-groove milling experiment of cemented carbide was conducted; the milling performance of three PCD micro ball-end mills was studied. Considering the surface morphology and roughness of the micro-groove machining, a single-edged hemispherical PCD micro ball-end mill can avoid the phenomenon of chip blocking and depositing and can also fully exert the grinding characteristics of PCD materials to obtain relatively better processing quality.

Experimental study on the meso-scale milling of tungsten carbide WC-17.5Co with PCD end mills

Tungsten carbide is a material that is very difficult to cut, mainly owing to its extreme wear resistance. Its high value of yield strength, accompanied by extreme brittleness, renders its machinability extremely poor, with most tools failing. Even when cutting with tool materials of the highest quality, its mode of cutting is mainly brittle and marred by material cracking. The ductile mode of cutting is possible only at micro levels of depth of cut and feed rate. This study aims to investigate the possibility of milling the carbide material at a meso-scale using polycrystalline diamond (PCD) end mills. A series of end milling experiments were performed to study the effects of cutting speed, feed per tooth, and axial depth of cut on performance measures such as cutting forces, surface roughness, and tool wear. To characterize the wear of PCD tools, a new approach to measuring the level of damage sustained by the faces of the cutter’s teeth is presented. Analyses of the experimental data show that the effects of all the cutting parameters on the three performance measures are significant. The major damage mode of the PCD end mills is found to be the intermittent micro-chipping. The progress of tool damage saw a long, stable, and steady period sandwiched between two short, abrupt, and intermittent periods. Cutting forces and surface roughness are found to rise with increments in the three cutting parameters, although the latter shows signs of reduction during the initial increase in cutting speed only. The results of this study find that an acceptable surface quality (average roughness $$R_{\text{a}} 600\,{\text{mm}}$$) can be obtained under the conditions of the given cutting parameters. It indicates that milling with PCD tools at a meso-scale is a suitable machining method for tungsten carbides.

Tool wear mechanisms in axial ultrasonic vibration assisted milling in-situ TiB2/7050Al metal matrix composites

The in-situ TiB2 particle reinforced aluminum matrix composites are materials that are difficult to machine, owing to hard ceramic particles in the matrix. In the milling process, the polycrystalline diamond (PCD) tools are used for machining these materials instead of carbide cutting tools, which significantly increase the machining cost. In this study, ultrasonic vibration method was applied for milling in-situ TiB2/7050Al metal matrix composites using a TiAlN coated carbide end milling tool. To completely understand the tool wear mechanism in ultrasonic-vibration assisted milling (UAM), the relative motion of the cutting tool and interaction of workpiece-tool-chip contact interface was analyzed in detail. Additionally, a comparative experimental study with and without ultrasonic vibration was carried out to investigate the influences of ultrasonic vibration and cutting parameters on the cutting force, tool life and tool wear mechanism. The results show that the motion of the cutting tool relative to the chip changes periodically in the helical direction and the separation of tool and chip occurs in the transverse direction in one vibration period, in ultrasonic vibration assisted cutting. Large instantaneous acceleration can be obtained in axial ultrasonic vibration milling. The cutting force in axial direction is significantly reduced by 42%–57%, 40%–57% and 44%–54%, at different cutting speeds, feed rates and cutting depths, respectively, compared with that in conventional milling. Additionally, the tool life is prolonged approximately 2–5 times when the ultrasonic vibration method is applied. The tool wear pattern micro-cracks are only found in UAM. These might be of great importance for future research in order to understand the cutting mechanisms in UAM of in-situ TiB2/7050Al metal matrix composites.

Experiment Analysis Research on Electrical Discharge Machining Polycrystalline Diamond Tool

As the hardest material in the field of synthetic materials, polycrystalline diamond has been paid more and more attention in the field of tools, which embody the basic characteristics of "high efficiency, precision and flexibility" of modern advanced cutting technology and cleaner production. Electrical discharge machining is typically used in processing polycrystalline diamond tools, especially in the machining of special shape, thin and fine cutting tools. In this paper, 2 micrometer and 10 micrometer polycrystalline diamonds are taken as the research object, and the surface quality of the disc electrode and wire electrode is simply compared by means of process and material test. The effects of diamond particle size, electrode polarity and electrode speed on the surface quality and the material removal rate of precision electrical discharge machining polycrystalline diamond are studied. The results show that there is no porous structure and no selectivity in discharge etching when the negative polarity electrode machine is used. With the increase of electrode rotation speed, the removal amount of polycrystalline diamond increases gradually, while the surface roughness of polycrystalline diamond decreases first and then increases. When the electrode linear velocity reaches 80 m/min, the surface roughness of polycrystalline diamond sample reaches the minimum value, and the removal amount of polycrystalline diamond material tends to be stable.