Diamond Stylus Research Articles

Energetic Size Effect Law at the Microscopic Scale: Application to Progressive-Load Scratch Testing

AbstractA scratch test consists in pulling a diamond stylus across the surface of a weaker material; it is widely applied in several fields of science and engineering, including polymer damage, metal wear, thin-film quality control, and strength of rocks. Recently, there has been an upsurge of interest in the fracture analysis of materials via scratch testing. In this study, the energetic size effect law (SEL) is applied at the microscopic scale for progressive-load scratch tests using a Rockwell C diamond probe. First, we employ dimensional analysis to connect the scratch force to the projected load-bearing area and to the perimeter for an axisymmetric scratch probe. In a second step, based on geometrical considerations, we approximate the real scratch probe geometry with a cone of equivalent half-apex angle, θeq. Then, we express the dependence of the nominal strength, σN, on the structural size, Λ, via a scaling relationship. The theoretical developments are later implemented in an experimental procedu...

Analysis of Abrasion Mechanisms in the AISI 303 Stainless Steel: Effect of Deformed Layer

Austenitic stainless steel is used in many industrial applications, especially those in which the corrosion resistance is relevant. However, this material is susceptible to surface damage, as well as the occurrence of phase transformations during manufacturing or even throughout use, since they present high work hardening. Therefore, the surface integrity cannot be neglected. This work aims studying the mechanical behavior of AISI 303 stainless steel during scratch tests. Analyses were conducted at the microstructural level, considering the presence of MnS inclusions. Scratch tests with normal loads on the order of mN were carried out using a diamond stylus to simulate the action of a single abrasive particle. The effect of surface finishing was evaluated by testing surfaces with mechanical or electrolytic polishing, which differ in terms of the presence (in the mechanical) or absence (in the electrolytic) of a deformed layer close to the specimen surface. The results allowed estimating the transition loads between abrasion mechanisms, from micro-ploughing to microcutting. These loads were determined for the different surface finishing. Preliminary numerical simulations were also included. In single abrasive operations, numerical results indicated the trend in decreasing the mass removed when the strain-hardened layer is considered.

Whole diamond stylus for the long play phonograph

Diamond styluses have long been used for long play (LP) phonographs, and remain favored by fans because of their higher fidelity to original sounds compared with compact disk (CD) digital media. In this paper, we report the fabrication and characterizations of a whole diamond stylus integrating the shaft and tip using a large single crystal diamond plate by sophisticated laser machining. This is the first moving magnet (MM) type LP cartridge comprising a whole diamond including the tip and cantilever. According to the frequency response measurements, whole diamond stylus has a lower crosstalk than the conventional stylus; that is, a far larger separation of the right and left channels e.g., 36dB @1kHz. For the 3rd harmonic distortion, which is the most important factor affecting the audio noise characteristics, the whole diamond stylus exhibits significant improvements compared with the conventional aluminum shaft cantilever; a 4dB improvement is observed in the frequency range of 500–800Hz, and a 3–5dB improvement is observed in the frequency range of 1300–1700Hz. Further improvements are expected to yield a well- designed cone-shaped tip over a wide range of frequencies including >20kHz, which was recently identified as the “audible” range for human.

Surface degradation of cemented carbides in scratching contact with granite and diamond–The roles of microstructure and composition

Cemented carbides are composite materials comprising metal carbide grains in a more ductile metallic binder. This microstructure results in a combination of high hardness and toughness, making them commonly used as rock crushing parts in rock drilling, where they usually show wear on a very fine scale. The hardness and toughness can ultimately be tuned for the application by adjusting the carbide grain size, binder fraction and composition.In the present investigation, the initial micro-scale deformation and wear of polished cemented carbide surfaces is studied by micro scratching with diamond and granite styli, and also by instrumented micro and nanoindentation. The deformation and wear is evaluated on the sub-micrometer scale using high resolution FEG-SEM and FIB cross sectioning. The selected microstructures include besides four cemented carbide grades that are commonly used in rock drilling also binderless and Ni containing grades. This wider range of cemented carbides is used to gain fundamental insights into the relations between microstructure and micro-scale deformation and wear. The results are discussed with respect to their significance for wear of cemented carbides in rock drilling operations.

Determination of wear volumes by chromatic confocal measurements during twin-disc tests with cast iron and steel

A novel method for in situ profile measurements on rolling contact test specimens has been demonstrated. A chromatic confocal probe was integrated into a twin-disc machine and used for disc profile measurements during periodically interrupted wear tests. The arrangement allowed detailed studies on the progress of the wear during a test without the removal of discs from the tribometer. Data from the interrupted tests was compared with the results of continuous tests. Both types of tests were run with two grades of cast iron dicsc in lubricated contact with steel. The results of this new method were in good agreement with those of a conventional diamond stylus probe method applied before and after the tests.

Erosive Effect of Different Soft Drinks on Enamel Surface in vitro: Application of Stylus Profilometry

Objective: To assess the erosive potential of various soft drinks by measuring initial pH and titratable acidity (TA) and to evaluate enamel surface roughness using different exposure times. Materials and Methods: The initial pH of the soft drinks (group 1: Coca-Cola; group 2: orange juice; group 3: Cedevita; group 4: Guarana, and group 5: strawberry yoghurt) was measured using a pH meter, and TA was measured by titration with NaOH. Enamel samples (n = 96), cut from unerupted human third molars, were randomly assigned to 6 groups: experimental (groups 1-5) and control (filtered saliva). The samples were exposed to 50 ml of soft drinks for 15, 30 and 60 min, 3 times daily, during 10 days. Between immersions, the samples were kept in filtered saliva. Enamel surface roughness was measured by diamond stylus profilometer using the following roughness parameters: R_a, R_q, R_z, and R_y. Data were analyzed by one-way ANOVA, Tukey's post hoc and Student-Newman-Keuls post hoc tests. Results: The pH values of the soft drinks ranged from 2.52 (Guarana) to 4.21 (strawberry yoghurt). Orange juice had the highest TA, requiring 5.70 ml of NaOH to reach pH 7.0, whereas Coca-Cola required only 1.87 ml. Roughness parameters indicated that Coca-Cola had the strongest erosion potential during the 15 min of exposure, while Coca-Cola and orange juice were similar during 30- and 60-min exposures. There were no significant differences related to all exposure times between Guarana and Cedevita. Strawberry yoghurt did not erode the enamel surface regardless of the exposure time. Conclusion: All of the tested soft drinks except yoghurt were erosive. Erosion of the enamel surfaces exposed to Coca-Cola, orange juice, Cedevita, and Guarana was directly proportional to the exposure time.

Pitch deviation measurement of an involute spur gear by a rotary profiling system

This paper presents surface-profiling based gear pitch deviation measurement for an involute spur gear. A rotary profiling system, which consists of an air-bearing spindle and a displacement sensor with a diamond stylus, is employed to measure gear pitch deviation. In measurement of gear pitch deviation, an eccentric error between a gear axis and a motion axis of the rotary stage in the profiling system would affect accuracy of gear profile measurement. In this paper, at first, the influence of the eccentric error on measurement of gear pitch deviation is estimated in computer simulation based on a geometric model of the profiling system. After that, a new scanning method named “opposite-direction dual scanning method” is proposed so that a steep profile of gear flank surface with a local slope of up to 90° can be measured by the developed rotary profiling system. For compensating distortions in the measured gear tooth profile, which are induced not only by the eccentric error but also by a probe offset introduced by the proposed scanning method, a self-calibration and compensation method is applied. To verify the feasibility of the proposed method, measurement of gear pitch deviation of a master involute spur gear with a certificate data is carried out. Measurement uncertainty of the proposed method is also analyzed.

The Method of Fillet Contour Error Compensation Applied in End Cylindrical Crankshaft Grinder

The Contour accuracy of a crankshaft transition fillet is important for the crankshaft working reliability. The front end surface, cylindrical surface and the transition fillet of a crankshaft are grinded by an end cylindrical grinder. During this machining, due to the roller’s shape error and other factors, the contour error of the fillet cannot be guaranteed while 90 degree circular arc interpolation was taken. In this paper, a fillet contour error compensation model was established, the appropriate compensation macro program was designed, and the radical contour error compensation was implemented through 9 circular arcs approaching. The practical application is shown that the satisfactory result is achieved and this method can also be applied in the fillet compensation for wheel dressing when applying diamond disk or stylus.

The influence of surface defects on the mechanical and tribological properties of VN-based arc-evaporated coatings

The influence of surface defects, i.e., droplets and craters, on the mechanical and tribological properties of arc-evaporated VxN coatings deposited on cemented carbide has been investigated in a scratching contact using a diamond stylus and a sliding contact using a stainless steel pin. Post-test characterisation using 3D optical surface profilometry and scanning electron microscopy was performed in order to investigate the mechanical and tribological response of the coatings. The results show that scratch induced coating cracking mainly is restricted to larger droplets showing a low interfacial bonding to the adjacent coating matrix. The influence of coating defects on the cohesive strength, i.e., the tendency to chipping of small coating fragments, was found to be relatively small. In contrast, the presence of defects may have a significant impact on the interfacial adhesive strength, increasing the tendency to spalling. In sliding contact, surface defects such as droplets and craters have a strong impact on the tribological behaviour of the coatings causing abrasive wear of the less hard counter material surface and material transfer to the coating, both mechanisms affecting the friction characteristics of sliding contact tribo systems.

Surface roughness and gloss study of prints: application of specular reflection at near infrared

Absolute reflectance data were measured with a spectrophotometer in the visible and near infrared (NIR) spectral range. The specular reflectance data in the NIR were used for the assessment of the surface roughness of magenta, yellow, cyan and black prints on paper. In addition, surface roughness data obtained from the prints with a mechanical diamond stylus, an optical profiling system and the spectrophotometer are compared with each other. The surface roughness obtained with the aid of the spectrophotometer data suggests a smoother surface than when measured with the diamond stylus and the optical profiling system. The gloss of the prints can be obtained from the absolute specular reflectance spectra in the spectral region of visible light. It is shown that specular reflection data at a fixed wavelength in the NIR are useful also in the interpretation of gloss in the visible spectral range, but using an unconventional grazing angle of incidence.

Microstructure and tribological properties of pulsed electric current sintered alumina–zirconia nanocomposites with different solid lubricants

Dense Al2O3-15wt% (ZrO2-3mol%Y2O3) nanocomposites modified with 3wt% of self-lubricating component (CaF2, BaF2, MoS2, WS2, h-BN, or graphite) were consolidated by pulsed electric current sintering. Their microstructure as well as mechanical and tribological properties were evaluated. During consolidation composition of the self-lubricating components was conserved except for BaF2, which partially melted. The Al2O3/ZrO2(3mol%Y2O3) matrix showed hardness of 20.35GPa and Young’s modulus of 320GPa determined by Vickers indentation. All solid lubricant additives led to a decrease in hardness of the composite. Solid lubricant additives lowered the coefficient of friction (CoF) against alumina at room temperature. In pin-on-disc tests CoF of 0.38–0.42 was measured for all the materials against alumina ball. The lowest CoF of 0.043 was measured for Al2O3/ZrO2(3mol%Y2O3)/CaF2 in the scratch test against diamond stylus while the matrix material showed lower friction than other materials. The measured wear rates were in the order of 10−12 for Al2O3/ZrO2(3mol%Y2O3)/CaF2, Al2O3/ZrO2(3mol%Y2O3)/MoS2, and Al2O3/ZrO2(3mol%Y2O3)/WS2.

Scratch testing of WC/Co hardmetals

Two grades of WC/Co hardmetals, a fine-grained sample and coarse-grained sample, were tested using single and multiple scratch tests with a spherical diamond stylus. The variation in damage mechanism with increasing number of scratch repeats was analysed using SEM, FIB and 3D confocal microscopy. An interesting feature is the formation of a thin tribo-layer on the surface of the scratched region, which becomes more evident at increased scratch repeats. Variations in the coefficient of friction were attributed to changes in the topography of the stylus and formation of a tribo-layer on the scratched surface.

Mechanical and Tribological Properties of PVD-Coated Cemented Carbide as Evaluated by a New Multipass Scratch-Testing Method

A new test method based on multipass scratch testing has been developed for evaluating the mechanical and tribological properties of thin, hard coatings. The proposed test method uses a pin-on-disc tribometer and during testing a Rockwell C diamond stylus is used as the “pin” and loaded against the rotating coated sample. The influence of normal load on the number of cycles to coating damage is investigated and the resulting coating damage mechanisms are evaluated by posttest scanning electron microscopy. The present study presents the test method by evaluating the performance of Ti0.86Si0.14N, Ti0.34Al0.66N, and (Al0.7Cr0.3)2O3coatings deposited by cathodic arc evaporation on cemented carbide inserts. The results show that the test method is quick, simple, and reproducible and can preferably be used to obtain relevant data concerning the fatigue, wear, chipping, and spalling characteristics of different coating-substrate composites. The test method can be used as a virtually nondestructive test and, for example, be used to evaluate the fatigue and wear resistance as well as the cohesive and adhesive interfacial strength of coated cemented carbide inserts prior to cutting tests.

S115021 広視野レーザ顕微鏡によるサブマイクロメートルの傷検査

In a previous work, we developed a new type laser microscope that has features of confocal scanning type and wide field of view. This new type of laser microscope was applied to detection of micro/nano-fine flaws over a wide area of 8 x 10mm on metal or glass surfaces. Several micro fine flaws were produced on stainless steel by scratching the surfaces with a diamond stylus. The fine flaws on the metal surfaces were able to be seen through the laser microscope we developed. Furthermore, submicrometer-flaws were produced on Si substrate or cylindrical-glass surface by focused ion beam technique, FIB. The surfaces containing those micro/nano flaws were observed with the laser microscope and the flaws on the Si substrate could be seen. It can be said that the flaws on the glass surface is slightly difficult to observe than those on the metal surfaces due to the wavelength of the laser we used.

S115023 微小領域におけるトライボロジー特性

This paper describes tribology in micro-scale order that is influenced by low friction force caused by low normal load. Recently, micromachines have been used in various fields. Tribolobical property in micro-scale such as micromachines move is known to be different as compared to macro-scale tribology. The aim of this research is to clarify microtribology and evaluate it. We selected diamond stylus tip and glass wafer as specimens in this research. In this experiment, friction force between two specimens is measured by using scratch tester. Besides, we observed friction groove and measured its depth with SEM. In conclusion, some knowledge about microtribology has clarified.

Ion beam forming of a shell type natural single crystal diamond stylus and sharpening of it by swinging a conical type diamond stylus

Natural single crystal diamond is used as a source material for diamond stylus employed in instruments for surface roughness measurement, and also used as diamond probe for AFMs due to ultra-high strength, ultra-high hardness, very-low friction coefficient, and so on. During the sharpening of diamond tools, facet formations at the tip and ripple formations at the cutting face (or at the tip's face) become problematic. We have successfully employed ion beam processing for the sharpening of diamond tools with small apex angles without any formation of facet or ripples. However, the sharpening conditions are limited to small areas only. Therefore, we introduced a new technique where a sample is swung during ion beam sharpening process to expand the processed area. We applied the technique for sharpening of a conical type diamond stylus and forming of a shell type diamond stylus by 1keV Ar+ ion beam at the swing angles of ±60° and ±90° respectively. Result shows that the facet or ripples were not formed on the processed surface. A simulation method is also developed for predicting the profile changes of diamond tools during ion beam machining at different swing angles.

Scratch Hardness of Polypropylenes: Effect of Applied Normal Force

A set of model polypropylene (PP) and talc-filled PP with various lubricants were prepared to study the effects of normal force on the scratch hardness of polymers. The effects of additives and annealing treatment on the scratch behavior of neat and talc-filled PP systems were investigated using a multiple-finger scratch test with focus on the influence of applied normal force on the scratch hardness. A way to revise the scratch hardness test method based on ASTM G171-03 (standard test method for scratch hardness of materials using a diamond stylus; ASTM International; West Conshohocken, PA) and ASTM D7027-05 (standard test method for evaluation of scratch resistance of polymeric coatings and plastics using an instrumented scratch machine; ASTM International; West Conshohocken, PA) is given. Differential scanning calorimetry and optical microscopy were used to characterize crystallinity, morphology, and scratch deformation mechanisms in the PP systems. It was found that the scratch hardness is related to the applied normal loads, the friction coefficient, and the fracture features generated during the scratch process. The talc-filled impact copolymer polypropylene (ICPP) exhibited higher scratch hardness than the neat ICPP. Homo-PP exhibited superior scratch resistance and less susceptibility to scratch deformation than ICPP. The addition of lubricant and annealing treatment improved the scratch resistance of both neat and the talc-filled PP systems.

Facet and ripple formations on single crystal diamond tools machined by low energy oxygen ion beam

In this paper, we have studied the facet and ripple formation on a hemispherical diamond stylus by low energy (0.3–3.0 keV) oxygen ion beam bombardment at different ion incidence angle. The sputtered stylus was observed by SEM. From SEM image, we measured the ion incidence angle θ max where the etching rate is maximum and compared them with the theoretical values of θ max derived from Witcomb formula. From experimentally and theoretically obtained values of θ max, we measured the facet angles of the processed hemispherical diamond stylus. Our result shows increasing discrepancy between theoretical and experimental values of both θ max and facet angle towards lower ion energy (< 2 keV) due to dominance of chemical sputtering over physical sputtering. From our observation we found a diamond stylus can be sharpened at 3 keV ion energy if the original apex angle is > 70°. We also observed surface morphology of the processed hemispherical diamond stylus machined by 0.3–3 keV oxygen ion beam at different tilted conditions. Our observation confirms the formation of ripple on the processed diamond stylus at higher angles of ion incidence. The ripple orientation at ion incidence 40°–60° processed by 3 keV oxygen ion beam is in well agreement with the predictions of linear BH model. However, ripples were not observed at near normal incidence and grazing incidence in contrast to BH model. In order to avoid ripple formation, the diamond stylus needs to be processed within the region of low ion incidence angles. The smoothing region is broader in the low ion energy range but some etch pits are seen to form in this region due to chemical sputtering of the impurities present in the diamond stylus.

The deformation and strength of a dental ceramic following resin-cement coating

Objectives The hypothesis tested was that processing, pre-cementation and cementation techniques can modify the profilometrically measured deformation of a ceramic. Methods Three-point flexural moduli of a resin-cement were characterised following light irradiation at 430 and 180 mW cm −2. Thirty IPS e.max Ceram discs were prepared and a reference surface produced by polishing. Discs were annealed, alumina particle air abraded and resin-coated. Profilometric evaluation was performed following each pre-cementation or cementation operative technique using a contact diamond stylus profilometer. Bi-axial flexure strength of the resin-coated discs, light irradiated at 430 and 180 mW cm −2 (Groups A and B), and the un-coated discs (Group C) was determined. Data were analysed by a one-way analysis of variance with post hoc Tukey tests ( P < 0.05), or repeat measure analyses when appropriate. Results Annealing (at 510 °C for 40 min) resulted in a significant reduction ( P < 0.001) in the characterised mean deflection, as did alumina particle air-abrasion ( P < 0.001). Resin-cement coating significantly increased the mean deflection for Groups A and B ( P < 0.001) specimens against the uncoated state. Furthermore no significant impact of increasing time or irradiation intensity on the mean deflection was identified. The mean bi-axial flexure strength was significantly increased ( P < 0.001) after resin-coating (Groups A and B) when compared with Group C specimens although no difference between Groups A and B specimens ( P = 0.291) was identified. Conclusion The results of the profilometric technique in combination with the strength supported a strengthening mechanism sensitive to shrinkage stress generation associated with the polymerisation of resin-cements.

Research on the Topography Feature of the Diamond Grinding Wheel under Elliptical Ultrasonic Assisted Dressing with Diamond Stylus

In this paper, topography feature of the diamond grinding wheel under the diamond stylus elliptical ultrasonic vibration assisted dressing was studied experimentally. The results indicate that: the increase in dressing power of elliptical ultrasonic vibration will result in the increase in amplitude, and that can increase abrasive protrusion height of the dressing grinding wheel, and also increase the depth of chip pocket. With the increase of feed rate, surface peak and valley values of elliptical ultrasonic vibration dressing grinding wheel increase, that is the average protrusion height of abrasive grain increases. With the increase of dressing depth, surface peak and valley values of elliptical ultrasonic vibration dressing grinding wheel increases, while the number of static effective abrasive grain reduces. In comparison with the ordinary dressing grinding wheel, elliptical ultrasonic assisted dressing in the same parameters can bring about more static effective abrasive grain , more uniform abrasive distribution, a higher abrasive protrusion height and more chip space.