Diamond Ball Research Articles

Analysis of topographic change by slide burnishing of C45 steel surface milled with variable number of inserts

The burnishing process’s positive changes in the material’s properties are measured with different responses. Roughness, stress, and microstructure changes are the main indicators of the internal and external factors faced by the material. Burnishing process as a post-process of critical components to enhance different properties performed by applying pressure on the material to deform plastically for the expected properties enhancement is used in different industries. In this experimental work, C45 steel was face milled by single and multiple-inserts and burnished with a 6mm diameter synthetic diamond ball to study the effect of burnishing force on the surface topography. 3D roughness parameters were used as response parameters measured before and after the burnishing process by AltiSurf 520 of Altimet as they are more representative of topographic changes by different machining processes and procedures than profile roughness parameters. Roughness was reduced significantly after the burnishing process in both cases and a decreasing trend was observed when compared at the same burnishing force.

Molecular dynamics study of the scratching property of the tetrahedral amorphous carbon coating on the piston ring

In order to reduce friction and wear of the piston ring-cylinder liner system of the internal combustion engine, the tetrahedral amorphous carbon (ta-C) coating on the piston ring is considered. The scratching properties of the ta-C coating and diamond ball are studied by molecular dynamics simulation. The atomic configuration, surface morphology, RMS roughness, friction force, coefficient of friction, wear rate, and normal stress of the ta-C coating are analysed under different scratching depths, substrate temperatures, and scratching velocities. The interatomic interactions are described using the second nearest-neighbour modified embedded-atom method potential, as well as Tersoff potential and Lennard-Jones potential. The simulation results show that the ta-C coating exhibits excellent scratching properties. The scratching depth has a significant effect on the scratching property of the ta-C coating, while the substrate temperature and scratching velocity have a relatively small effect.

Influence of Abrasive Grain Protrusion on High-Quality Machining of Cemented Carbide Using PCD Ball End Mills

In this study, cemented carbide was machined to a high quality using polycrystalline diamond (PCD) ball end mills characterized by various surface textures. The effect of the surface texture of the tools on the machining characteristics was studied using two types of PCD tools featuring abrasive diamond grains at various protrusion heights. In addition, a single crystal diamond tool with the same shape as that of the PCD tool was fabricated, and the experiment was repeated to study the differences in machining characteristics. The polished PCD tool yielded a high-quality machined surface with an average surface roughness of 1 nm. The polished PCD tool yielded superior sample surface roughness compared to the PCD tool for feed rates of 10–500 mm/min. The use of a polished PCD tool enables the efficient elimination of material through plastic flow, leading to the attainment of a high-quality machined surface while preventing the adhesion of materials on the tool surface. A single crystal diamond tool can also be used for machining cemented carbide within a feed rate range of 10–200 mm/min; however, its performance is inferior to that of a polished PCD tool. Experiments confirmed that the polished PCD tool was the most effective among the tested tools for the precision machining of cemented carbide.

A comparative study on tribological behavior of Al2O3, AlN, Si3N4 and ZrO2 ceramics sliding against polycrystalline diamond ball

Studying the tribological behavior between diamond materials and ceramics is crucial for understanding the grinding mechanism of diamond wheels on ceramics. To comprehend the tribological characteristics between diamond materials and various ceramics, this paper presents a comparative study of the tribological behaviors of Al2O3, AlN, Si3N4, and ZrO2 ceramics sliding against polycrystalline diamond (PCD) balls. The dependence of the coefficient of friction (COF), wear characteristics as well as the surface morphology of different ceramics and SiC-bonded PCD balls on load, sliding stage were examined. The effect of nanofluids on the COF and wear of different ceramics was also investigated. The results showed that the tribological characteristics of ceramic materials are strongly dependent on mechanical properties. Al2O3 and AlN ceramics with lower fracture toughness exhibit a significantly higher COF and wear volume than that of Si3N4 and ZrO2 ceramics. Al2O3 presents the highest COF (0.38) and wear volume, and Si3N4 owns the lowest COF (0.08) and wear volume under the load of 9.8 N. By examining the wear grooves of different ceramics, it is found that Al2O3 and AlN ceramics own larger debris than that of Si3N4 and ZrO2, which also causes more smearing on the ceramic and adhesion of wear debris to the SiC-bonded PCD ball for Al2O3 and AlN. Under lubricants, the COFs and the adhesion of wear debris are effectively reduced, and the wear rate of the ceramic is increased. There is little difference between deionized (DI) water and nanofluids on the effect of lubricants on COF for Al2O3 and AlN. However, for ceramics with higher fracture toughness, the nanofluids can reduce the COFs of Si3N4 and ZrO2 in comparison with DI water.

Achieving Diamond-Like Wear in Ta-Rich Metallic Glasses.

Most metals and alloys suffer from high friction and wear due to their low hardness and lack of self-lubrication. Although plenty of strategies have been proposed, it is still a long-standing challenge to achieve diamond-like wear in metals. Metallic glasses (MGs) are supposed to possess low coefficient of friction (COF) because of their high hardness and fast surface mobility. However, their wear rate is larger than that of diamond-like materials. Here, this work reports the discovery of Ta-rich MGs that exhibit diamond-like wear. This work develops an indentation approach for high-throughput characterization of crack resistance. By employing deep indentation loading, this work is able to efficiently identify the alloys that exhibit better plasticity and crack resistance according to the differences of indent morphology. With high temperature stability, high hardness, improved plasticity, and crack resistance, the discovered Ta-based MGs exhibit diamond-like tribological properties, featured by COF as low as ≈0.05 for diamond ball test and ≈0.15 for steel ball test, and specific wear rate of only ≈10-7 mm3 N- 1 m-1 . The discovery approach and the discovered MGs exemplifie the promise to substantially reduce friction and wear of metals and may unleash the potential of MGs in tribological applications.

A Novel Force Control Strategy for Improved Surface Integrity in Low Plasticity Burnishing

Ball burnishing is a cold work process where a hard ceramic or diamond ball rolls on a metal surface and flattens the roughness peaks under high local pressure. The small deformation created on the surface imposes compressive residual stresses and raises hardness in a shallow sub-surface layer, leading to improved fatigue, corrosion, and foreign object damage performances. Trial-and-error type experimental work to determine the optimum process parameters for a cold-forming process like ball burnishing for acceptable performance is costly. Therefore, the article aims to investigate the effects of various force control strategies in the double-sided low plasticity burnishing (LPB) process to find the effects on deformation and residual stresses on thin Ti6Al4V flat sheets. A 3D static-implicit finite element model was developed with an elastic-rigid plastic flow curve. Simulations were conducted to predict residual stresses and deformationі on the surface. As a result, it was proven that ball burnishing can produce a deterministically controlled surface. An increased vertical force produced higher deformation normal to the surface and, therefore, a deeper pool. As the ball proceeded further, a plowing effect developed such that when a 3.5–4.8 mm deep pool was formed (at a vertical force of 150 N), a peak of 2.8 mm was produced at the front end. Overall, the deformation on the surface and the residual stresses were directly interrelated. Parallel to the deformation on the surface, residual stresses on and beneath the surface also showed some variation. Nevertheless, the predicted residual stress variations were not big. They did not switch to the tensile mode in the burnished zone. Therefore, the whole sheet surface should be burnished to obtain all the compressive residual stresses.

ИССЛЕДОВАНИЕ АДГЕЗИОННОЙ СОСТАВЛЯЮЩЕЙ КОЭФФИЦИЕНТА ТРЕНИЯ ИНДЕНТОРА ИНСТРУМЕНТА С ПОВЕРХНОСТЬЮ ДЕТАЛИ ПРИ ОБРАБОТКЕ МЕТОДАМИ ПОВЕРХНОСТНОГО ПЛАСТИЧЕСКОГО ДЕФОРМИРОВАНИЯ

The paper presents the results of studying the parameters of the contact interaction between the tool indenter and the work surface of parts while machining by methods of surface plastic deformation by diamond smoothing and ball burnishing. Changes in the technological factors of diamond smoothing and burnishing under relatively equal machining conditions have different effects on the formation of the topography and parameters of the microprofile. This is due to the contact character of the indenter with the surface. When diamond smoothing, the indenter is rigidly fixed in the tool holder, whereas for ball burnishing the indenter rotates. Accordingly, sliding friction prevails for smoothing, and rolling friction prevails for burnishing. Friction forces in the contact area of the tool indenter with the surface of the part affect the processes. Friction coefficient depends on the deformation and adhesive components. The processes of plastic deformation of metal, the quality of the work surface and other machining parameters in the contact area of the indenter with the work surface are greatly influenced by the strength of the adhesive bond and the molecular component of the friction coefficient. The values of these factors are determined by the combination of materials of the contacting surfaces. This information is often not available in the reference and scientific sources, and theoretical calculations do not allow taking into account real machining factors. The paper presents the methodology and some results of studying the molecular component of the friction coefficient, the specific strength of the adhesive bond and the pressure coefficient in the contact area of the indenter with the surface during diamond smoothing and ball burnishing. The presented results give the scientific novelty of the paper.

Dynamic characteristics of abrasive grains and machined surface features for variable axis diamond grinding of quartz glass

There is a fine application prospect for multi-axis grinding of hard and brittle materials with diamond ball end tool. The effects of tool inclination angles and grinding modes of multi-axis grinding of quartz glass on the dynamic characteristics of the diamond abrasives, surface topography, surface fragmentation phenomenon, and surface roughness were investigated in this work. Material removal characteristics and surface formation conditions would be significantly affected by the effective cutting speed, material stress characteristics, and movement space path derived from different grinding modes and tool inclination angles. The surface texture direction is mainly determined by feed direction of the cutter and initial cutting moment and geometry feature of the engaged diamond abrasives. The surface fragmentation phenomenon of the formed surface is apparent when the corresponding surface roughness values are relatively larger. The machined surface with significant surface fragmentation phenomenon is mainly produced by materials' brittle fracture modes, such as larger positive lead and smaller negative tilt under conventional grinding and smaller negative lead angles and larger positive tilt angles under down grinding. Ideal surface evenness could be obtained by using lead or tilt 0° for conventional and down grinding. The ground surface with smaller surface roughness could be produced when employing tool postures, such as negative lead or positive tilt under conventional grinding and positive lead or negative tilt under down grinding condition.

THE INFLUENCE OF THE MULTILAYER STRUCTURE OF HARD COATINGS ON THEIR RESISTANCE TO MICRO-IMPACT FATIGUE WEAR

Fatigue cracking of thin hard anti-wear coatings occurs, among others, in the tribological contact of sliding friction pairs, in the top layers of cutting tools coatings, as well as in the surface of elements subjected to erosion processes. Coating fatigue wear is initiated as a result of cyclic interactions with micro-roughness of counterpart or other elements or particles that repeatedly impact the surface. The selection of appropriate coatings can increase the durability of machine components that are subjected to fatigue impact loads. The paper presents the results of tests on micro-impact fatigue wear of elements covered with single TiN and DLC coatings, as well as multi-layer (Ti/TiN)×8 type. Fatigue tests were carried out using the micro-impact method by cyclic impact of the surface of the coating with a diamond ball. The experiments were performed using a special laboratory stand. The correlation between fatigue life of coatings and their micromechanical properties such as Young's modulus and hardness were also examined. The hardness and Young's modulus were determined by an instrumented indentation method. The test results proved that the (Ti/TiN)×8 multilayer coating demonstrates wear 1.4 times smaller than the sample with the TiN coating and 1.2 than the sample with the DLC coating.

Temperature changes in bone using an air scaler Ex Vivo

Introduction Frictional forces induced by osteotomy devices may induce an unwanted temperature increase in bone. This experimental study aimed to evaluate temperature changes produced in dense bone by three different osteotomies produced by an air scaler device. Methodology Under the same parameters, forty-five linear osteotomies were prepared on the cortical layer of fresh porcine ribs resembling dense bone with three different air scaler insert tips: sagittal saw (Tip A), diamond ball (Tip B) and square chisel (Tip C). The length of the osteotomies was standardized to 10 mm in length. The depths of cuts ranged from 0.5 mm to 2.0 mm. The future osteotomy areas were marked with a graphite pen, and thermocouple microprobes were placed 1 mm lateral at both sides of the marks. The maximum temperature, differential temperature, and time for cut completion were recorded. Analysis of Variance and Kruskal Wallis test were used for the group comparisons. Results Tip A induced the highest of the maximum temperature recordings (Tip A: 48.0 o C). Tip B and C produced comparable maximum temperatures (Tip B: 43.6 o C and Tip C: 44.0 o C). Total mean temperature change increased more for Tip B (4.13) and less in Tip C (0.2). Timing of cuts ranged from 30 seconds to 5 minutes (2.30 ± 1.76 min). Overall average temperature change was less than 100 o C within one minute. Conclusion Osseous site preparation can be achieved with the Air scaler and different air scaler inserts without inducing significant critical thermal changes in bone.

Surface hardening of 36 NiCrMo 6 steel by ball burnishing process

This work aims to characterize the 36 NiCrMo 6 steel in monotic traction. The tested samples were subjected to mechanical surface treatment (MST) by diamond ball burnishing. This process allow it possible to modify the physical and geometrical properties of the material. The stress-strain diagram obtained were processed and digitalised. The hardening domain was modelled and rational curves were established, taking into account the stresses triaxiality. Thus, the work hardening exponent of material considered was evaluated. The effect of ball burnishing on this exponent has studied in proceeding a comparative manner between burnished and machined surface. The results obtained show that by applying the optimal parameters for burnishing, the work hardening exponent of pre-machined surface layer can be increased by 10%, where nB = 0.407 (nT = 0.312 machined surface).

Study on End Brush Deburring and Sintered Diamond Ball Deburring of Micro-features Milled

The presence of top burr in the micro-features produced by milling process can deteriorate and affect the surface quality of the products. Though there are some deburring methods can be used and reported successfully remove the burr in the micro scale features, however simpler and alternative method is still needed. Two of the deburring methods that can be used are end brushing and sintered diamond ball methods. Therefore the aim of this paper is to study the application of the end brush and sintered diamond ball for deburring top burrs exist on micro features produced by milling process. Slot milling experiments were conducted and subsequently deburring process using the two methods was conducted. Micro scale features were also produced using milling process followed by deburring. The deburred results were observed visually using optical microscope and Scanning Electron Microscope (SEM) and surface roughness was measured. Experimental results show that the end brush and sintered diamond ball deburring have successfully remove the top burrs. The end brush deburring method produced better surface quality compared to the sintered diamond ball.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ НАПРЯЖЕННО-ДЕФОРМИРОВАННОГО СОСТОЯНИЯ В ПОВЕРХНОСТНО УПРОЧНЕННЫХ ВТУЛКАХ С УЧЕТОМ ОСТАТОЧНЫХ КАСАТЕЛЬНЫХ НАПРЯЖЕНИЙ

We suggest the phenomenological mathematical model of the stress-strain state reconstruction in the surface hardened thin-walled tube with an inner diameter 45 mm and outer diameter 51.5 mm made of steel EI961 and treated by diamond smoothing of the outer surface. It is shown that if all stress components depend on radius only, then the components are in the cylindrical coordinate system. The experimental research is made for the samples which were softened under two load modes (radial force) of the diamond ball attachment of 200 and 300 N value. The experimental values of residual stresses , , and in the surface layer are obtained by the ring and strip method using the layer-by-layer electrochemical pickling of the hardened layer. The experimentally measured values of the strip beam deflection, split ring angular opening and axial displacement of cut edges relative to each other are used for this purpose. The hardening anisotropy parameter which relates the axial and circumferential components of plastic strain is included in the mathematical model. To solve the formulated problems we use the hypotheses of plastic incompressibility of the material, the absence of secondary plastic deformations of the material in the surface layer compression area and the hypotheses of flat sections and straight radii. We present the method for solving the stress-strain state reconstruction boundary value problems, which allows obtaining the missing component and all residual plastic strain components. The validation of the computational data obtained by mathematical modelling for adequacy to the experimental data for the two modes of hardening is made. There is a close agreement between the computational and experimental data. The numerical values for the hardening anisotropy parameter are given. By using this parameter we are able to theoretically describe the observable experimental layering of axial and circumferential stresses in depth of the hardened layer. It is theoretically and experimentally established that the absolute values of maximum shear stresses is an order of magnitude smaller than the absolute values of maximum normal stresses. We also discuss the questions of the effect of shear stresses on high-cycle fatigue and creep of the hardened thin-walled tubes. The main results of the research are illustrated by the tabular data and corresponding diagrams of the residual stresses distribution in depth of the hardened layer.

Modelling of surface formation mechanism during burnishing of aluminium

Burnishing is a finishing process which levels the roughness of machined surfaces and increases the hardness by micro-forming. In this paper, a novel two-dimensional finite element model for the diamond ball burnishing process on aluminium is presented, which allows a prediction of the surface structure. The force, step over distance, and tool geometry during the burnishing process are taken into account by the model and the results are verified by experimental investigations. The verification shows that the model is able to predict all geometrical surface aspects like roughness, sinking-in and bulge formation for reasonable process parameters.

Hard particle effect on surface generation in nano-cutting

The influence of the hard particle on the surface generation, plastic deformation and processing forces in nano-cutting of aluminum is investigated by means of molecular dynamics simulations. In this investigation, a hard particle which is simplified as a diamond ball is embedded under the free surface of workpiece with different depths. The influence of the position of the hard ball on the surface generation and other material removal mechanism, such as the movement of the ball under the action of cutting tool edge, is revealed. The results show that when the hard particle is removed, only a small shallow pit is left on the machined surface. Otherwise, it is pressed down to the subsurface of the workpiece left larger and deeper pit on the generated surface. Besides that, the hard particle in the workpiece would increase the processing force when the cutting tool edge or the plastic carriers interact with the hard particle. It is helpful to optimize the cutting parameters and material properties for obtaining better surface quality in nano-cutting of composites or other materials with micro/nanoscale hard particles in it.

Topographical orientation effects on surface stresses influencing on wear in sliding DLC contacts, Part 2: Modelling and simulations

The effects of surface roughness and topographical orientation on surface stresses influencing wear have been investigated for diamond like carbon (DLC) coated steel surfaces with three levels of surface roughness in the range of 0.004–0.11μm Ra values, and with topographical groove orientations of 0°, 45° and 90°. A novel multiscale numerical finite element method (FEM) model was developed to integrate the layered and microstructural material features with the grooved topography. Fractal geometry and a surface voxelisation based approach were utilised to derive 3D surface topography. The surface texture representation includes: fractal signatures, which are sets of fractal dimensions calculated at individual scales in different directions, texture aspect ratio describing surface anisotropy, and texture direction signatures calculated by the variance orientation transform (VOT) method. The simulations show details of the main topographical orientation effects on local stresses affecting wear as they appear at a single scratch test with a spherical diamond ball and in a self-mated sliding situation of two rough surfaces. The 45° sliding direction in relation to grooves resulted in a mixed state of surface loading in the scratch test contact. In the complex state of stress-strain within the roughness peaks the overall tensile stress decreased, leading to greater surface resistance to cracking as compared to 0° and 90° directions. Model based calculations showed that the surface structure was about four times more rigid in the direction of grooves as compared to the more flexible behaviour in the perpendicular direction. This behaviour was empirically confirmed. The numerical calculations of rough vs rough sliding surface include real surface topographical features at various scales, material microstructural features down to nano-scale and topographical-microstructural interaction features. This approximation is thus more comprehensive than the classical approach. The real area of contact was 15–30% of the apparent contact area. The macro-topography dominated the tendency for surface cracking and plastic deformation, which is influencing on both wear and friction, while the micro-topographical features contributed to cracking and deformation by less than 40%.

Surface Quality for Rotary Ultrasonic Milling of Quartz Glass Employing Diamond Ball End Tool with Tool Inclination Angle

Nowadays, quartz glass is widely used in many industry fields. The machined surface quality is an important issue in the ultrasonic milling of quartz glass with diamond ball end tool. This paper analyzed the movement characteristics of the engaged cutting abrasive particles and investigated the effects of spindle rotation speed, feed speed, width of cut, and depth of cut on the machined surface topography and surface roughness. Also, comparisons of machining effects with and without ultrasonic were carried out. In general, application of ultrasonic vibration needs to cooperate with other process parameters to give play to the advantages of RUM, and ultrasonic function could not necessarily improve the formed surface. Comparing with conventional milling, reasonable selection of process parameters could decrease the machined surface roughness under the premise of achieving a high materials removal rate for RUM.

Fretting wear of composite ceramic coating produced on D16 aluminum-based alloy using microarc oxidation

The mechanism of the wear of a composite ceramic coating, which has been produced on the D16 aluminum-based alloy using microarc oxidation, under low-amplitude reciprocal friction (fretting) is studied. The ball-on-plane arrangement in which a diamond ball slides reciprocally against a flat specimen covered with the microarc-oxidation coating is considered. The three following regions of the fracture of the coating have been identified: the moderate wear range, which is characterized by a constant wear rate and in which a smoothed wear spot is formed; the severe wear range, which is characterized by the partial delamination of the top layer of the coating; and the extreme wear range, which is characterized by the cracking of the coating through its entire thickness up to the metal. Based on the experimental results, the boundary of the transition to the inoperative region of the extreme wear of the coating has been determined over the entire ranges of the load and displacement under study.

Effect of Diamond Ball Burnishing on Surface Characteristics and Fatigue Strength of XC55 Steel

Investigation on the effect of surface quality of lathe machined down XC55 steel work piece on the fatigue strength has been carried out. The mechanical surface treatment was achieved by elastic-plastic cold working in the near-surface region through a ball burnishing finishing operation. The results showed improvement in surface roughness (Ra) from 1.49 µm to 0.45 µm and increase in hardness (Hv) from 300.8 to 537.35. These were in good agreement with results predicted from a mathematical model based on full factorial experiment method. The fatigue strength of pieces subjected to ball burnishing revealed 40% and 30% high resistance then those pieces that have respectively undergone lathe turning and grinding. This was due to compressive residual stresses that the burnishing process generated on the outer surfaces.

Analysis and modelling of the dry-sliding friction and wear behaviour of electrodeposited Ni and Ni-matrix-nanocomposite films

The work here described aimed to assess the tribological behaviour of a Ni-matrix-nanocomposite film and to gain understanding of the role that the reinforcing phases play in it. The composite consisted of an array of Ag-coated SnO2 nanowires grown onto a substrate, around which the Ni matrix was galvanostatically deposited. Friction and wear were evaluated under dry sliding conditions using a linearly reciprocating ball-on-flat setup, with a diamond ball of 5.8µm radius as counterbody, subjected to loads ranging from 5 to 30mN. The surface and cross section of the wear tracks were characterised by scanning electron microscopy, energy-dispersive X-ray spectroscopy and white light interferometry. Ploughing-type abrasive wear was observed, with load-dependent dynamic friction coefficients, being this attributed to scale effect. Numerical models were developed for the analysis of wear volume and wear rate, as function of film hardness, applied load and wear track length. Due to their higher hardness, the composite films exhibited superior wear resistance with respect to Ni films produced using the exact same bath and deposition parameters as the composite׳s matrix. This was evidenced by reductions of up to 74 and 65% in wear volume and rate, respectively.