Scratch Behavior Research Articles

Input power effect on microstructure and mechanical properties of Mo[sbnd]Si[sbnd]N multilayer coatings

The MoSiN single layer and multilayer films were fabricated by a reactive radio frequency, r.f., magnetron sputtering system with pure Mo and Si targets. The Ar/N2 flow ratio was fixed at 12/8, while r.f. input powers for Mo and Si were 135 W and 0 to 150 W, respectively. The corresponding Si contents in the coating ranged from 0 to approximately 20 at.%. The microstructure of the MoSiN single layers evolved from Mo2N (111) crystalline to amorphous feature with input powers and related Si doping amounts. The MoSiN multilayer coatings were fabricated with crystalline MoN, crystalline and amorphous MoSiN layers with sequential stacking of any two building layers. The multilayer film made of MoN and crystalline MoSiN layers showed an obvious crystalline microstructure, while the amorphous MoSiN layer incorporated multilayer MoSiN systems effectively suppressed the continuity of the columnar growth. The correlation between mechanical properties, including hardness, Young's modulus, indentation cracking, and scratch behavior, were investigated and discussed in terms of film microstructure evolution.

The Neuropeptide Y Y2 Receptor Is Coexpressed with Nppb in Primary Afferent Neurons and Y2 Activation Reduces Histaminergic and IL-31-Induced Itch.

Itch stimuli are detected by specialized primary afferents that convey the signal to the spinal cord, but how itch transmission is regulated is still not completely known. Here, we investigated the roles of the neuropeptide Y (NPY)/Y2 receptor system on scratch behavior. The inhibitory Y2 receptor is expressed on mouse primary afferents, and intrathecal administration of the Y2 agonist peptide YY (PYY)3-36 reduced scratch episode frequency and duration induced by compound 48/80, an effect that could be reversed by intrathecal preadministration of the Y2 antagonist BIIE0246. Also, scratch episode duration induced by histamine could be reduced by PYY3-36 In contrast, scratch behavior induced by α-methyl-5HT, protease-activated receptor-2-activating peptide SLIGRL, chloroquine, topical dust mite extract, or mechanical itch induced by von Frey filaments was unaffected by stimulation of Y2 Primary afferent neurons expressing the Npy2r gene were found to coexpress itch-associated markers such as natriuretic peptide precursor b, oncostatin M receptor, and interleukin (IL) 31 receptor A. Accordingly, intrathecal PYY3-36 reduced the scratch behavior induced by IL-31. Our findings imply that the NPY/Y2 system reduces histaminergic and IL-31-associated itch through presynaptic inhibition of a subpopulation of itch-associated primary afferents. SIGNIFICANCE STATEMENT: The spinal neuropeptide Y system dampens scratching behavior induced by histaminergic compounds and interleukin 31, a cytokine involved in atopic dermatitis, through interactions with the Y2 receptor. The Y2 receptor is expressed by primary afferent neurons that are rich in itch-associated neurotransmitters and receptors such as somatostatin, natriuretic peptide precursor b, and interleukin 31 receptors.

In-situ synthesis of Ti–Al intermetallic compounds coating on Ti alloy by magnetron sputtering deposition followed by vacuum annealing

In this study, a thin Ti–Al intermetallic compounds (IMCs) coating was in-situ synthesized on a titanium alloy substrate through magnetron sputtering of Al followed by vacuum annealing. The microstructure, composition distribution, nanoindentation and microhardness, scratch and wear behavior of the obtained Ti–Al IMCs coating were investigated. It was found that TiAl3 is formed at the surface, and very thin TiAl and Ti3Al layers exist between the TiAl3 layer and the substrate. The microhardness of the TiAl3 (11.17 GPa) is almost twice as that of the substrate (6.03 GPa), and no cracking occurs during the indentation process. Microstructure observation and composition analysis suggest that metallurgical bonding is formed between the Ti–Al IMCs coating and the substrate, leading to a high bonding strength and almost no peeling during the whole scratch test. The tribological test reveals that the Ti–Al IMCs coating exhibits a lower friction coefficient and a much lower wear rate than those of the substrate, and the major wear mechanism of the Ti–Al IMCs coating is abrasive wear. Based on the findings, the in-situ synthesis of Ti–Al IMCs coating via magnetron sputtering followed by vacuum annealing can be considered a promising method to effectively improve the wear resistance of the Ti alloy.

Unravelling the abrasion resistance of two novel meta-stable titanium alloys on the basis of multi-pass-dual-indenter tests

Multi-pass-dual-indenter (MPDI) scratch tests with various loading conditions were performed on two newly developed titanium alloys (Ti–10V–1Fe–3Al and Ti–10V–2Cr–3Al) to investigate their abrasion resistance under repetitive local sliding contact. A technically pure titanium sample was used as the reference. Various microstructures were established by different heat treatments, such as to turn the β-phase into a stable phase or a meta-stable phase showing Stress Induced Martensite (SIM) formation. The influence of phase evolution on the scratch resistance and corresponding failure mechanisms was unravelled. It was found that the phase morphology and fraction have a significant impact on the scratch resistance and that effect is applied load dependent. The scratch behaviour is closely related to the work hardening ability of the material surface especially at high loading conditions, while the original surface hardness is more relevant at low loading conditions. The observations definitely prove that, not withstanding the modest hardness level, a microstructure showing a combination of metastable β (trigger the stress-induced martensitic transformation) and flake α (enhancing the initial surface hardness) is the best route to improve the scratch resistance for these two titanium alloys, in particular for high load conditions.

Nanoindentation and scratch behaviour of Ni–P electroless coatings

ABSTRACTIn the present paper, the mechanical properties and the scratch failure mechanisms of Ni–P electroless coatings are described. The material microstructure was studied in as-deposited and annealed conditions through SEM and EDS analyses. Nanoindentation measurements on the coatings showed a remarkable hardening due to the crystallization and precipitation behaviour produced by annealing. The scratch tests, conducted by increasing the load during scratch, revealed the coating failure mechanisms in a broad range of applied stresses up to delamination.

Influence of processing variables on scratch and shrinkage behaviors and translucency of dental zirconia

AbstractScratch tests were performed on porous 3 mol% Y2O3‐stabilized zirconia dental blocks to relate compaction processing and partial sintering temperature to shrinkage and machinability of the blocks and microstructures and transmittance after full sintering. Scratch hardness of the blocks varied with increasing loads, and the variation was related to the sequential events of densification, densification and cleaving, disruption of the densified region, and chipping and longitudinal cracking. The shrinkage during final sintering was inversely proportional to the compact pressure and temperature with compact pressure having a greater impact. In contrast, the transmittance of fully sintered blocks depended largely on the partial sintering temperature because it governed the number and size of pores after completion of the sintering. Based on the influence of the variable on scratch hardness, a scratch response measure that possibly reflects the machinability of porous CAD/CAM blocks was proposed.

Synthesis and Characterization of Scratch-Resistant Ni-P-Ti-Based Composite Coating

In order to improve the toughness of Ni-P coatings, Ti particles were introduced into the plating solution to produce a Ni-P-Ti composite coating (on API-X100 steel), which was subsequently annealed to form superelastic NiTi precipitates within the coating. The effect of Ti content on deposition rate and surface morphology of Ni-P-Ti coatings was studied. A detailed investigation of the influence of Ti content and annealing on the microstructure, microhardness, and scratch behavior of Ni-P-Ti composite coatings was carried out. Further, scratch resistance and toughening mechanisms, namely, crack deflection, crack bridging, and crack shielding, are discussed. The NiTi precipitates greatly improved the cracking and scratch resistance as a result of the superelastic NiTi toughening effect.

Comparative Investigation and Characterization of the Scratch and Wear Resistance Behavior of TiN, CrN, AlTiN and AlCrN Cathodic Arc PVD Coatings

The scratch resistance and wear behavior at relatively high normal loads of binary (TiN, CrN) and ternary (Al0.50Ti0.50N, Al0.68Cr0.32N) coatings were comparatively investigated. Scratch test results showed that based on the adhesive strength the coatings can be ranked thus: CrN > TiN > Al0.68Cr0.32N > Al0.50Ti0.50N. The binary coatings were found to possess superior adhesion strength mainly exhibiting a tensile cracking failure mechanism. In contrast, the ternary coatings failed more severely by through-thickness cracking with spallation. The ternary coatings exhibited an average of 68, 67 and 55% improvement in the wear resistance at 15, 20 and 25 N normal loads, respectively, over the binary coatings. Abrasive and oxidation wear were the main wear mechanisms of the binary coatings. The formation of protective tribo-oxide layers is associated with the improved wear resistance behavior of the ternary coatings. High surface roughness due to large amount of surface defects coupled with low plastic deformation resistance and high Al content are reasons for low wear resistance of Al0.68Cr0.32N in comparison with Al0.50Ti0.50N coating.

Scratch behavior of model epoxy resins with different crosslinking densities

The scratch behavior of model epoxy resins with varying degrees of crosslink density was investigated according to the ASTM D7027/ISO 19252 scratch test methodology. Three model epoxy systems with low, medium, and high crosslinking densities were prepared to systematically investigate how the scratch behavior might be influenced. The effect of crosslinking density on the onset of groove, crack and plowing formation during scratching was investigated. Coefficient of friction measurements, uniaxial tensile and compressive stress-strain curves, and dynamic mechanical analyses were conducted to correlate the intrinsic material properties to the observed scratch-induced deformation of the model epoxy systems. The findings indicate that the scratch behavior of epoxy resins can be directly correlated to their material properties. It is found that both the tensile strength and compressive yield stress determine the resistance against damage formation during scratch. Additionally, a comparison between pencil hardness and scratch test is presented to assess the suitability of both methods for evaluating scratch performance of polymers with significantly different mechanical properties.

The effect of plasma polymerization of silicon compounds on the properties of biaxially oriented polypropylene (BOPP)

In this study, hexamethyldisiloxane was polymerized on the biaxially oriented polypropylene films by low-pressure radio frequency (RF) plasma. The samples were polymerized by using RF plasma in the frequency range of 13.56 MHz at the different polymerization times. The surface properties and chemical structure of samples were examined by contact angle measurement, atomic force microscopy, scanning electron microscopy and Fourier transformation infrared (FTIR). Also, the scratch behavior and the mechanical properties of samples were evaluated by using SPM lithography. In this work, some distinguishing changes were observed in properties of polymerized samples in comparison with raw sample. Results showed that the scratch resistance increased by prolonging polymerization time, whereas the surface energy decreased dramatically. It can be inferred from SPM and FTIR data that there is a direct relationship between scratch resistance and chemical composition of samples. Scratch resistance is mostly affected by silicon compounds deposited on the samples. Plasma polymerization causes changes in the chemical structure and surface properties of samples.

Influence of nano-silica and polyethylene wax on the scratch behavior of acrylic-based polyurethane coatings

The scratch behavior and resistance of acrylic-based polyurethane coatings were studied. The effects of fumed silica and polyethylene wax were investigated using an area-contact scratch tip, which can apply a constant load to the coating surfaces at a relatively low stress level. Measurements of the normalized changes in gloss (%Gn) and luminance (%Ln) could be provided as reliable and meaningful methodologies for estimating the scratch resistance and subtle damage to polymeric coating surfaces. A higher gloss-valued coating surface has better scratch resistance. The addition of nano-silica particles provides the increases in hardness, transparency, and resistance to scratch damage for the acrylic-based polyurethane surface, whereas the polyethylene wax contributes to the increases in gloss and smoothness for the coating surface. The surface characteristics observed are responsible for the improved scratch performance of the acrylic-based polyurethane coating surface.

Preparation and tribological characterization of graphene incorporated electroless Ni-P composite coatings

Industrial application of electroless NiP coatings are limited by their low toughness and cracking under various loading conditions that in turn requires improvement of toughness using ternary coating systems. In this research work, graphene suspension was added to electroless NiP plating bath in various concentrations to produce four different compositions of Ni-P-G (graphene) coatings. Micro-structural and surface attributes were studied using SEM and white light profilometer respectively. Scratch and indentation behaviors of substrate and coatings were investigated. Graphene incorporation in NiP coating matrix improved the hardness as well as wear resistance. Also graphene supported NiP coating exhibited toughness through crack shielding and crack deflection phenomena.

Fabrication and investigation of the scratch and indentation behaviour of new generation Ni-P-nano-NiTi composite coating for oil and gas pipelines

Oil and gas pipelines operate under severe mechanical and chemical conditions, which could lead to catastrophic failure. Electroless nickel-phosphorous (Ni-P) coatings are an excellent candidate for protection against wear and corrosion for oil and gas pipelines. Ni-P coatings exhibit superior corrosion resistance over many commercially available coatings, as well as high hardness. However, electroless Ni-P coatings suffer from low toughness, which has limited its use in applications where high scratch and dent resistance is required. To enhance the toughness of the Ni-P coatings, nano-sized particles of superelastic NiTi alloy were incorporated within the coating. In the present work novel Ni-P-nano-NiTi composite coating has been successfully plated on API X100 pipe steel. Scratch tests under constant and increasing loads were performed to determine the effect of NiTi nano-particles on wear damages. Indentation tests were carried out to assess the dent resistance and crack modes of the coating. The addition of superelastic nano-particles into the Ni-P matrix led to toughening through transformation toughening, crack bridging, deflection, and microcracking. The composite coatings exhibited lower hardness in comparison to monolithic Ni-P coatings, but still provided considerable improvement upon the steel substrate. Optical and scanning electron examinations showed evidence of delamination, radial, and Hertzian cracking, as well as a reduction in crack length with the addition of superelastic NiTi.

Effect of molecular weight on scratch and abrasive wear behaviors of thermoplastic polyurethane elastomers

The effect of molecular weight on scratch and abrasive wear behaviors of three model thermoplastic polyurethane (TPU) elastomers was examined. In this study, the model TPU samples investigated were synthesized to contain different molecular weights, but with the same type and ratio of hard and soft segments. Within the range of molecular weights examined, it is found that increasing the molecular weight improves the tensile strength of the TPU samples. The variation in molecular weight has minimal influence on the morphology and surface friction of the samples. Furthermore, this study indicates that a higher molecular weight is associated with improved resistance against scratch onset of cracking/material removal and abrasive wear volume loss. Implications of the present study for the design of scratch and abrasive wear resistant TPU are discussed.

Manufacturing of a Metal Matrix Composite Coating on a Polymer Matrix Composite Through Cold Gas Dynamic Spray Technique

In this work, the manufacturing through cold gas dynamic spray (cold spray or CS) of metallic composite coatings of Al-Al2O3 on organic composite substrates with thermoplastic PLA matrix and hemp fibers was studied. Alumina powders, with a mean diameter of 50 μm, were used blended with aluminum powders in three different weight concentration percentages (0, 15, 20, and 45%) as feedstock material in order to highlight and discuss the variations of the coating surface properties depending on the alumina percentage. The coatings were produced by using a low-pressure cold spray equipment. A detailed experimental campaign, including microstructural observations and confocal microscopy, was carried out to study the structure of the coatings. Moreover, the tribological behavior of the coatings was studied through both scratch test and pin-on-disk test. The experiments showed that a small addition of alumina improves the compactness of the coating and its resistance to scratch and wear behavior.

Scratch behavior and FEM modelling of Cu/Si(100) thin films deposited by modulated pulsed power magnetron sputtering

A series of copper thin films on Si(100) substrate were deposited using the modulated pulsed power magnetron sputtering under a sputtering pressure from 0.11 to 0.70 Pa. The scratch behavior of Cu/Si(100) thin films was characterized by the critical loads (Lc1–4) with the aid of finite element method (FEM) simulation. Increasing the sputtering pressure, surface morphology became rougher and the cross-sectional pattern transformed from compact fine granular to coarse and crack visible columnar structure. The Cu thin films scratched were continuous and comparative intact at 0.11 Pa which occurred to be with the highest critical loads, then gradually went to vast delamination initiated at 0.30 Pa with the Lc decreasing accordingly. The maximum principal stress (σ1) calculated by FEM was employed to evaluate the transition of critical loads Lc1–Lc4 using the typical stress concentration zones A, B and C which were the zones under, around and at the sides of the scratch tip, respectively. For the Cu/Si(100) thin films with strong adhesion, the Lc1 and Lc2 were evaluated through the migration of σ1 peak from the zone B to C, while the Lc3 and Lc4 were associated with stress accumulation at the zone C and A. The scratch behavior of Cu/Si(100) thin films was quantitatively expressed with the aid of FEM simulation.

Investigation of the tribological behavior of chromium aluminum silicon nitride coatings via both scratch sliding test and FEM simulation

The finite element method (FEM) and scratch sliding test were combined to investigate the tribological behaviors of Chromium Aluminum Silicon Nitride (CrAlSiN) coatings with various Si contents. The tribological behavior was evaluated through sliding tests using a conventional ball-on-disc wear apparatus. It was found that the coefficient of friction (COF) of CrAlSiN was lower than CrAlN coating and it reached a minimum value of 0.56 for CrAlSi3.7N. Energy-dispersive Scanning Electron Microscopy (SEM) with X-ray spectroscopy (EDX) was employed to reveal the compositions of wear debris formed during the scratch sliding experiments. As a reasonable approximation, a static condition was applied, and the scratch behavior was modeled by a sphere indenter scratching on a thin coating coated on a thick substrate. A three-dimensional finite element model was constructed with the help of the ABAQUS to describe the mechanical response during scratch.

Mechanical properties of heat-treated duplex electroless nickel coatings

ABSTRACTElectroless nickel coatings present complementary properties: coatings formed using hypophosphite present usually better corrosion resistance while those made with borohydride present better mechanical and wear properties. Duplex coatings, combining both kinds of deposits, are designed to combine features of both nickel–phosphorus (ENP) and nickel–boron (ENB) coatings. In this study, monolayer and bilayer coatings were synthesised on mild steel substrates, in various combinations of ENP and ENB, with a total thickness of 20 µm and heat treated (400°C – 1 h) under non-reactive atmosphere (95% Ar–5% H2) to enhance their mechanical properties. The morphology, roughness, hardness, abrasive wear resistance and scratch behaviour of the coatings were investigated. Samples with ENP as the top layer showed a higher roughness than samples with ENB as the external layer. However, samples with ENB as the top layer provided better wear resistance, even if they presented a lower combined hardness. ENB monolayer showed the best resistance to scratch testing.

Load effect on scratch micro-mechanisms of solution strengthened Compacted Graphite Irons

Abstract This study investigates the scratch load effect, from 100 to 2000 mN, on micro-mechanisms involved during scratching. A pearlitic and three ferritic Compacted Graphite Irons (CGI) solution strengthened through addition of 3.66, 4.09, and 4.59 Si wt% were investigated. Good correlation was observed between hardness measurements, tensile testing, and scratch results explaining the influence of matrix characteristics on scratch behaviour for investigated alloys. A significant matrix deformation, change in frictional force and scratch coefficient of friction was observed by increase in scratch load. In all cases, microscratch depth and width increased significantly with load increasing, however pearlitic CGI showed most profound deformation, while the maximum and minimum scratch resistances were observed for high-Si ferritic and pearlitic CGI alloys, respectively.

The use of volcanic particles in HDPE offers alternative filling material against CaCO3. Part II—scratch properties

This article clarifies that the influence of volcanic particles (VPs) and calcium carbonate particles (CaCO3) on the scratch behavior of high‐density polyethylene (HDPE). Melt compounding was carried out using a twin‐screw microcompounder and then injection molding with various VPs and CaCO3 contents such as 0, 6, 12, 18, and 24 wt% was performed for preparing test samples. Scratch testing was performed using the testing apparatus and methodology outlined in ASTM D7027–05 with 60 mm/min scratch velocities of 200 μm stainless steel ball bearing scratch tip. Coefficient of friction (COF) and scratch hardness values of various VPs‐ and CaCO3‐filled HDPE composites were determined. Results showed that COF and scratch hardness values were improved with higher inorganic particle concentrations. It was found that VPs was more effective filler for the scratch properties of HDPE than CaCO3. After scratch tests, scratch damage mechanisms were analyzed by scanning electron microscopy. POLYM. COMPOS., 40:2564–2572, 2019. © 2018 Society of Plastics Engineers