Scratch Speed Research Articles

Novel Combined Scratch and Nanoindentation Experiments on Soda‐Lime‐Silica Glass

Many advanced applications of glass demand fabrication of engineering parts of utmost dimensional precision which require very accurate grinding and polishing that involves controlled removal of glass. Despite the wealth of literature, however; the mechanism of material removal in glass grinding and polishing is still far from well understood. For instance, it is not known at all to what extent the mechanical properties are compromised inside a scratch groove so as to optimize the machining parameters. Therefore, to develop better understanding about the mechanism of material removal, a series of combined nanoindentation and single pass scratch experiments were conducted on a commercially available soda‐lime‐silica glass as a function of various normal loads (2–20 N) and scratch speeds (0.1–1 mm/s). It was found that the nanohardness and Young's modulus at the local microstructural length scale inside the scratch groove could decrease quite dramatically (~30% to 70%) depending on the combination of load and scratching speed. Further, the tribological properties, the severity and the spatial density of damage evolution were sensitive to the normal loads, scratching speeds, and tensile stresses. Extensive scanning electron microscopy leads to interesting observations on material removal mechanisms. These observations were explained by the theoretical predictions of a model for a brittle, microcracked solid.

Nanopatterning on silicon surface using atomic force microscopy with diamond-like carbon (DLC)-coated Si probe.

Atomic force microscope (AFM) equipped with diamond-like carbon (DLC)-coated Si probe has been used for scratch nanolithography on Si surfaces. The effect of scratch direction, applied tip force, scratch speed, and number of scratches on the size of the scratched geometry has been investigated. The size of the groove differs with scratch direction, which increases with the applied tip force and number of scratches but decreases slightly with scratch speed. Complex nanostructures of arrays of parallel lines and square arrays are further fabricated uniformly and precisely on Si substrates at relatively high scratch speed. DLC-coated Si probe has the potential to be an alternative in AFM-based scratch nanofabrication on hard surfaces.

The study of nanoscratch and nanomachining on hard multilayer thin films using atomic force microscope

In this study, nanoscratching and nanomachining were conducted using an atomic force microscope (AFM) equipped with a doped diamond-coated probe (DDESP-10; VEECO) to evaluate the fabrication of nanopatterns on hard, Cr₂N/Cu multilayer thin films. The influence of normal force, scratch speed, and repeated scratches on the properties of hard multilayer thin films was also investigated. The nanoscratch experiments led researchers to establish a probe preparation and selection criteria (PPS criteria) to enhance the stability and accuracy of machining hard materials. Experimental results indicate that the depth of grooves produced by nanoscratching increased with an increase in normal force, while an increase in the number of scratches in a single location increased the groove depth but decreased friction. Therelationships among normal force and groove depth more closely resembled a logarithmic form than other mathematical models, as did the relationship between repeated scratching and its effect on groove depth and friction. The influence of scratch speed on friction was divided into two ranges. Between 0.1 and 2 µm/s, friction decreased logarithmically with an increase in scratch speed; however, when the speed exceeded 2 µm/s, the friction appeared stable. In this study, multilayered coatings were successfully machined, demonstrating considerable promise for the fabrication of nanopatterns in multilayered coatings at the nanoscale.

Deformation and material removal in a nanoscale multi-layer thin film solar panel using nanoscratch

Amorphous Si thin film solar panels are multi-layer structures consisting of nanometric layers of hard and brittle materials. The deformation and material removal characteristics of the panel cross-section were investigated using nano-mechanical testing. Nanoindentation and nanoscratching were performed using indenters of various geometries at a range of loads. Atomic force microscopy and electron microscopy were used to study the resulting deformation structures and mechanisms. Plastic deformation of the brittle layers was observed below a critical scratch depth, where material removal occurred without fracture. The critical depth was found to be dependent on indenter geometry and material properties. The indenter tip with the smallest included angle resulted in the greatest scratch depths and material removal. The increased scratching speed also improved the removal efficiency. The results of this work can be applied to develop the ductile regime machining process for thin film solar panels.

Adhesion failure behavior of sputtered calcium phosphate thin film coatings evaluated using microscratch testing

It is generally accepted that calcium phosphate (CaP) is one of the most important biomaterials in implant coating applications mainly because of its excellent bioactivity. However, its relatively poor mechanical properties limits its application. This entails that a better understanding of the mechanical properties of a CaP coating is a must especially its behavior and the mechanisms involved when subjected to stresses which eventually lead to failure. The mechanical properties of the coating may be evaluated in terms of its adhesion strength. In this study, a radio frequency-magnetron (RF-MS) sputtering technique was used to deposit CaP thin films on 316L stainless steel (SS). The coatings were subjected to series of microscratch tests, taking careful note of its behavior as the load is applied. The adhesion behavior of the coatings showed varying responses. It was revealed that several coating process-related factors such as thickness, post-heat treatment and deposition parameters, to name a few, affect its scratching behavior. Scratch testing-related factors (i.e. loading rate, scratch speed, scratch load, etc.) were also shown to influence the mechanisms involved in the coating adhesion failure. Evaluation of the load–displacement graph combined with optical inspection of the scratch confirmed that several modes of failure occurred during the scratching process. These include trackside cracking, tensile cracking, radial cracking, buckling, delamination and combinations of one or more modes.

Scratching properties of nickel-iron thin film and silicon using atomic force microscopy

Atomic force microscopy (AFM) is well known for its ability for nanopatterning many different materials. The patterning technique using an AFM tip as a scratch tool, known as scratch nanolithography, is used to study the scratch characteristics of 80% Permalloy thin film and silicon, with the emphasis on establishing their scratchability or the nanoscale machinability. The effects of the scratch parameters, including the applied tip force, scratch speed, and number of scratches, on the size of the scratched geometry were specifically evaluated. The primary factors that measure the scratchability were then identified and the governing material properties for scratchability were evaluated. To demonstrate its versatility, the scratching technique was applied to fabricate a NiFe-based nanoconstriction, which is used for many ferromagnetic devices. All results indicated that NiFe thin film has much better scratchability than that of Si and the scratched groove geometry can be accurately correlated with and precisely controlled by the tip normal force.

Microstructure and properties of TiAlSiN coatings prepared by hybrid PVD technology

TiAlSiN coatings with different Si content were prepared by hollow cathode discharge (HCD) and mid-frequency magnetron sputtering (MFMS) hybrid coating deposition technology. The chemical composition, microstructure, mechanical properties of these coatings were systematically investigated by means of energy dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nanoindentation measurement, scratch and high speed milling hardened steel tests. The coatings prepared by this method showed the structure of crystalline phase was corresponding to that of TiAlN, however, different preferred orientation with addition of Si. Proper content of Si into TiAlN led to increase of microhardness and adhesion. TiAlSiN coated end mill with Si content of 4.78 at.% had the least flank wear, which was improved about 20% milling distance than TiAlN coated end mill.

Deformation of SS 304 LN during Scratch Test and Influence on Evolution of Coefficient of Friction

An AISI 304 LN nuclear grade forged, metallographically polished specimen was subjected to progressive load scratch tests using a spheroconical indenter at three different scratch speeds 1, 3, and 27 mm/min. The present study attempts to address the evolution of coefficient of friction with scratch speed invoking its correlation with scratch induced deformation in the specimen. At higher scratch speeds, plastic deformation rates were higher which caused friction coefficient to be of higher magnitude. This was correlated with dynamically obtained high resolution optical images that revealed deformation driven microstructural alterations. These alterations significantly influenced the evolution of friction coefficient which was intimately related to plasticity of the surface.

Influence of scratch load and speed in scratch tests of bilayer powder coatings

The knowledge of the properties of the coatings in terms of scratch and wear resistance is of paramount importance in order to prevent the formation of severe damages. Nonetheless, dealing with the evaluation scratch or wear resistance of an organic coating can be troublesome. They can be strongly dependent on the status of the organic material as well as on the contact condition, applied load and strain rate. Besides, reliable responses cannot be achieved if an appropriate experimental design and a combined usage of proper equipments is not scheduled. In this respect, the present analysis deals with the application of variable speed and load scratch tests to characterize the scratch response and wear resistance of bilayer metal flakes powder coatings. Experimental findings allowed the achievement of consistent trends of the deformation response vs. curing temperature, scratch load and speed as well as their empirical modelling. This way, the overall scratch resistance of the bilayer coatings could be usefully predicted on a broad range of operational conditions, thus providing helpful indications to paint manufacturers and coaters on how to best deal with the application of metal flake powders.

On the combined use of scratch tests and CLA profilometry for the characterization of polyester powder coatings: Influence of scratch load and speed

The prediction of the mechanical properties of polyester powder coatings is of paramount importance, as they have to undergo a wide variety of forces and deformations during their service life. Determine the response of polymeric coatings to the actual loading conditions can be, however, very troublesome as their properties are function of the material physical state, rate-dependence and yield and break behaviour. Further, the characterization of soft, contaminated organic surfaces such as polymers can often cause severe problems with reliability and imaging accuracy due to instrumental artefacts. This is therefore the context in which this paper investigates the capability of multiple parameters scratch tests joined with non-contact CLA profilometry and FE-SEM to detect the scratch response of polyester powder coatings for protective and decorative outdoor applications. Scratch tests with blunt contact geometry were used to evaluate the response of polyester coatings baked at different time–temperature programs and, so, at different stages of their curing process. In particular, being such coatings highly non-linear in their response to mechanical stress or strain, the influence from scratch load and speed was carefully taken into account. Analytical evaluations of the experimental results led to good correlations between the extent of the deformed zone after scratch, scratch parameters and curing operational settings. This allows mapping the scratch response of the polyester topcoats to broad ranges of both scratch parameters and curing conditions.

Mechanism of Material Removal and the Generation of Defects by MD Analysis in Three-Dimensional Simulation in Abrasive Processes

Molecular dynamics (MD) simulations of nanometric scratching with diamond tip are conducted on single crystal copper crystal plane (010), and MD simulations are carried out to investigate the mechanism of material removal and the generation of defects on the surface, subsurface and inner of material. During the process of diamond tip scratching the surface of single crystal copper on conditions of different scratching speeds, depths and widths. We achieved the forming details of the chip. While the generation and moving process of defects, such as dislocation, are recorded. The different times of atomic displacement and interaction force are also shown through MD simulation. The evolvement of the lattice pattern in the abrasive processes are analysed by radial distribution function (RDF) and computing the changes of workpiece’s atomic displaces and forces. At the same time, the lattice reconfiguration and the onset and the evolvement process of defects and are analysed by RDF and atomic perspective method, respectively. The simulation results show that scratching speed play role in the course of the form of removing chips, and that different scratching widths and depths of tool have effect on onset and evolvement of lattice defects of workpiece in abrasive processes. This study can give more fundamental understanding of nanosconstruction from atomistic motions and contribute to the design, manufacture and manipulation of nano-devices

Plastic deformation modes of gallium arsenide in nanoindentation and nanoscratching

The mechanical deformation by nanoindentation and scratching of gallium arsenide has been investigated using cross-sectional transmission electron microscopy. Twinning was found to be the main deformation process occurring during indentation while only slip bands and perfect dislocations are observed during scratching. This behavior is explained, in the authors’ experiments, with the strain rate in scratching being hundred times greater than in indentation. Hence, the low indentation velocity allows twins to be nucleated and propagated from surface inhomogeneities, whereas in scratching, the deformation occurs first in front of the indenter and the scratching speed allows only perfect α dislocation to propagate.

Kinematics of a single abrasive particle during the industrial polishing process of porcelain stoneware tiles

In order to achieve glossiness the porcelain stoneware tiles must undergo an industrial polishing process, which can be optimized by either the scratching phenomena or the polishing kinematics. This paper is focused on the latter. Thus, the most important kinematic equations involved in polishing process were described. The lateral oscillation used in modern polishing machines, as well as the other available motions were taken into account. The trajectory of abrasives, the scratching speed and the curvature radius could be obtained for each instant. The importance of adopting good kinematics parameters for the accomplishment of the polishing process was highlighted, and the equations furnished hereby serve as useful tools for further attempts in optimizing the polishing process.

Influence of experimental factors and film thickness on the measured critical load in the nanoscratch test

A model system showing clear film failure in nanoscratch tests, Si-containing a-C:H film on glass, was selected to investigate the influence of various experimental parameters on the measured critical load in the nanoscratch test. No dependence on critical load was found for this system on either (1) scratch speed, (2) loading rate, or (3) increase in load per unit scratch distance (d L/d x) when d L/d x is much less than 1 N/mm, whilst critical loads only slightly increase at higher d L/d x (1–5 N/mm). This suggests that tests under widely different loading conditions can be compared directly in contrast to what has been reported for conventional macro-scale scratch testing where d L/d x is set to 10 N/mm and results are strongly dependent on both loading rate and scan speed. It has also been found that the film thickness has a marked influence on the critical load in the nanoscratch test. The role of the ratio (hardness/modulus) on the linear increase in critical load with film thickness is discussed.

Deformation mechanisms of silicon during nanoscratching

AbstractThe deformation mechanisms of silicon {001} surfaces during nanoscratching were found to depend strongly on the loading conditions. Nanoscratches with increasing load were performed at 2 µm/s (low velocity) and 100 µm/s (high velocity). The load‐penetration‐distance curves acquired during the scratching process at low velocity suggests that two deformation regimes can be defined, an elasto‐plastic regime at low loads and a fully plastic regime at high loads. High resolution scanning electron microscopy of the damaged location shows that the residual scratch morphologies are strongly influenced by the scratch velocity and the applied load. Micro‐Raman spectroscopy shows that after pressure release, the deformed volume inside the nanoscratch is mainly composed of amorphous silicon and Si‐XII at low scratch speeds and of amorphous silicon at high speeds. Transmission electron microscopy shows that Si nanocrystals are embedded in an amorphous matrix at low speeds, whereas at high speeds the transformed zone is completely amorphous. Furthermore, the extend of the transformed zone is almost independent of the scratching speed and is delimited by a dislocation rich area that extends about as deep as the contact radius into the surface. To explain the observed phase and defect distribution a contact mechanics based decompression model that takes into account the load, the velocity, the materials properties and the contact radius in scratching is proposed. It shows that the decompression rate is higher at low penetration depth, which is consistent with the observation of amorphous silicon in this case. The stress field under the tip is computed using an elastic contact mechanics model based on Hertz’s theory. The model explains the observed shape of the transformed zone and suggests that during load increase, phase transformation takes place prior to dislocation nucleation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Evaluating abrasive wear of amorphous alloys using nanoscratch technique

The hardness and elastic modulus of several Zr, Pd, Cu, and La-based amorphous alloys were investigated using nanoindentation. Abrasive wear of these alloys was also evaluated and compared using nanoscratch techniques under a ramping load. Damage caused by scratching was examined using SEM. Material pile-up took place in all scratched samples, but to different degrees. The scratched surface was observed to be significantly different for alloys with different compositions. A modified Archard equation was derived for the ramping load test. It was found that the wear resistance of amorphous alloys does not follow the classical Archard equation, i.e. the wear resistance is not linearly proportional to the hardness. This discrepancy was suggested to be a result of different wear mechanisms operating in different materials. The wear resistance of a Pd-based alloy was found to be independent of scratch speed.

Development of a scratch test in an autoclave for the measurement of repassivation kinetics of stainless steel in high temperature high pressure water

The slip-dissolution model of stress corrosion cracking states that crack tip advance is based on active dissolution of metal atoms after film rupture and until fill repassivation has occurred. The repassivation phenomenon can be investigated using a scratch test. After a stainless steel sample is polarized in the passive part of the anodic polarization curve, a sharp pin makes a scratch on the surface, hereby removing the passive film. Repassivation of the bared metal in the scratch will occur due to the applied potential. The current supplied to the metal sample is measured before, during and after scratching. A device has been designed that can perform such a test in an autoclave. A ceramic pin produces a scratch on a stainless steel sample when a metal bellow expands under a burst internal pressure. Typical problems encountered include the well controlled movement of the ceramic pins, scratch reproducibility and proper current measurement. Furthermore, a finite scratching speed results in mixed activation/repassivation, i.e. repassivation starts before the scratch is finished. A convolution calculation has been made to tackle this problem. The paper discusses the design and experimental procedure of the scratch test and some experimental results obtained in high temperature water (300 °C). Mathematical modeling of the repassivation current shows good correlation with experimental data. The mathematical model allows for a slow scratching speed and circumvents some of the disadvantages of conventionally fast scratch tests.

Nanoscratch evaluation of adhesion and cohesion in SiC/low-k/Si stacked layers

A nanoscratch method combined with atomic force microscope and transmission electron microscope observations was used to estimate the adhesive and cohesive strengths of SiC/low-k/Si stacked layers with the aim of correlating the fracture strength with the results of chemical mechanical polishing (CMP) tests. It was found that the friction coefficient was an effective signal for detecting the occurrence of failure in the microstructure during the scratch test. Fracture strength was characterized using the critical normal load at the first abrupt decrease in the friction coefficient. A specimen (A) having a low-k layer with a lower modulus and lower hardness displayed a lower friction coefficient, a lower critical load, and ductile adhesive failure resulting from delamination at the interface between the low-k layer and Si substrate. In contrast, a specimen (B) having a low-k layer with a higher modulus and higher hardness exhibited a higher friction coefficient, a higher critical load and brittle cohesive failure that occurred in the low-k layer. It was also found that specimen A always had a higher critical load level than specimen B regardless of the scratching speed, loading rate, and stylus radius. Dependence of the critical load on specimen thickness was also examined. These nanoscratch measurements corresponded with the results of the CMP process, which suggests that the process characteristics can be predicted with this nanoscratch method.

Scratch Hardness of Stone Models-Measuring Conditions

This study investigated the effects of scratch load, scratch speed, and storage period of specimen on the scratch hardness of stone models. Types 4 and 5 stone specimens were made from vinyl silicone rubber and alginate impressions respectively. After specimens were stored in a desiccator with silica gel at room temperature for 24 hours or 1 week, scratches were created on the surface with three different scratch loads (1N, 2N, and 3N) and two different scratch speeds (50 and 100 mm/min). Then, the depths of scratches were measured. Scratch depth of stone specimens increased with increasing scratch load. Scratch depths of Type 4 stone specimens after 1-week storage were smaller than those after 24-hour storage at a speed of 100 mm/min. However, the effect of scratch speed on scratch depth did not follow a specific trend.

A new test methodology for evaluating scratch resistance of polymers

A new approach to conduct scratch tests on polymers is proposed. A brief review of the different definitions of scratch resistance and surface damages, currently available scratch test devices and the need for such a new approach is given. The new test methodology is developed using the concepts from materials science and solid mechanics, which include the consideration of material parameters, use of microscopy for image analysis and the finite element method (FEM). The consistency and reproducibility of test results are shown using a new scratch test device on two sets of neat and talc-filled polypropylene (PP) systems. Three different test conditions, i.e. linear load increase under constant speed, constant load under constant speed, and linear speed increase under constant load, have been conducted to determine the most effective, informative test conditions for evaluation of scratch resistance of polymers. The effect of loading and scratch speeds on the scratch-induced deformation of PP is also investigated using FEM simulations. Experimental observations and FEM results show a good qualitative correlation. The unique advantages of the new scratch test method for evaluating scratch resistance of polymers are discussed.