Papers by Keyword: Scratch Resistance

Abstract: The use of hydroxyapatite (HA) coating on metallic implants has always been a challenge due to a discrepancy between ceramic coating and metallic substrate properties. In this study, functionally graded TiO₂-HA coating (FGC TiO₂-HA), with bottom-up composition: 100% TiO₂, 50% TiO₂ -50% HA, 100% HA, produced by sol-gel method on the Ti-6Al-4V alloy substrate. The XRD, FTIR and DSC results signified desired phase achievement. The quality assessment and scratch resistance of FGC TiO₂-HA in comparison with control samples (single-layer HA and double-layer TiO₂-HA coatings) were assessed by SEM and FESEM images and nanoscratch test. According to the tests outcomes, The TiO₂ intermediate layer increases the HA coating’s strength (22%) and surface hardness, while gradient layer of TiO₂-HA improves (14%) this consequence by progressing the coating integrity.

Abstract: The present study focuses on scratch behaviour of a conventional pearlitic and a number of solid solution strengthened ferritic Compacted Graphite Iron (CGI) alloys. This was done by employing a single-pass microscratch test using a sphero-conical diamond indenter under different constant normal loads conditions. Matrix solution hardening was made by alloying with different content of Si alloy; (3.66, 4.09 and 4.59 wt%. Si) which are named as low-Si, medium-Si and high-Si ferritic CGI alloys, respectively. A good correlation between the tensile and scratch test results was observed explaining the influence of CGI’s matrix characteristics on scratch behaviour both for pearlitic and fully ferritic solution strengthened ones. Both the scratch depth and scratch width showed strong tendency to increase with increasing the normal load, however the pearlitic one showed more profound deformation compared to the solution strengthened CGI alloys. Among the investigated alloys, the maximum and minimum scratch resistance was observed for high-Si ferritic CGI and pearlitic alloys, respectively. It was confirmed by the scratched surfaces analysed using Scanning Electron Microscopy (SEM) as well. In addition, the indenter’s depth of penetration value (scratch depth) was found as a suitable measure to ascertain the scratch resistance of CGI alloys. Keywords: Silicon solution strengthening, CGI, Abrasion, Scratch testing, Scratch resistance

Abstract: The scratch damage resistance and impact strength of PMMA sheets are necessary factors that have to be concerned by manufacturers. The aim of this work is to investigate the influences of silica (Si) from tetraethoxysilane on scratch damage resistance of the sheet surfaces for optical applications. The polymeric composites including PMMA, polyurethane (PU) and Si were produced via a bulk polymerization in a casting process. The technique creates semi-interpenetrating polymer networks (IPNs) between PMMA and PU. The percentage of IPNs and surface morphology of the composite sheets were observed. Furthermore, scratch resistance, impact strength, ultraviolet and thermal degradations of PMMA-PU-Si sheets were measured and compared with those of neat PMMA-PU sheets. The results revealed that the optimal Si amount (0.039 phr) provided 2B of the scratch resistance (2B of pencil range). This composite formula gave the highest impact values of 24.27 kJ/m² for an Izod type and 24.94 kJ/m² for a Charpy type. Composite sheets showed increases in ultraviolet and heat resistance by increasing the content of Si. However, the PMMA-PU-Si sheets were useable at temperature lower than 180 ^⁰C.

Abstract: The scratch resistance of the silicon nitride with the addition of 1 and 7 wt% of graphene multiplatelets prepared by hot press sintering has been studied. The scratch resistance behaviour of Si₃N₄-GNP composites were investigated using a Rockwell indenter for normal applied loads ranging from 1-150 N. Si₃N₄-7-wt%GNP composite behaved differently during the scratch test depending on the normal applied load. The coefficient of friction changed dramatically at higher load and extensive crack propagation resulting in the chipping is observed.

Abstract: Cr/CrN multilayers with a bilayer period λ = 62 ÷ 1000nm, were investigated. They were deposited by PLD technique on austenitic and ferritic stainless steel substrates. Coating hardness and adhesion to substrates were measured by nanoindentation and scratch testing. Multilayer properties were compared with single Cr and CrN coatings. The 2xCr/CrN and 4xCr/CrN multilayers exhibited hardness slightly lower than the hardness of a single CrN coating, while the critical load of the 4xCr/CrN multilayer, measured in the scratch test, was two times higher than for CrN. Furthermore, the character of coating failure also indicates the higher fracture toughness of multilayers than ceramic ones. The highest scratch resistance of the hardest multilayer with a bilayer period λ = 250nm is extremely interesting. The measured values of the critical loads L_C1 and L_C2 of all coatings were higher for harder ferritic than austenitic substrates. However, analysis of scratch track geometry indicated that coating failure occurred under the same deformation of the coating-substrate system, while the higher values of critical load for coatings on ferrite derived from the higher hardness of the substrate.

Abstract: Multilayers of alternate Ti/TiN coatings deposited on X20Cr13 ferritic stainless steel by pulsed laser deposition (PLD) method have been tested using instrumented indentation. The effect of bilayer period and metal/ceramic thickness ratio were studied.

Abstract: Effects of h-BN particles on mechanical properties and adhesion of semi-crystalline poly (ether-ether-ketone) (PEEK) coatings were studied. PEEK powder was mixed with various contents of h-BN nanoparticle in ethanol under ultrasonic mixing. As-mixed powders were sprayed onto low carbon steel substrate with thermal spray technique. The hardness, scratch hardness, specific scratch wear rate, prevailing deformation mechanisms and adhesion were obtained from scratch tests by varying the applied load. The damage geometry on scratched polymer surfaces and scratch wear volume loss were examined using scanning electron microscope (SEM) and surface profilometer, respectively. The results indicated that the addition of h-BN content improved the hardness of the composite. In addition, the specific scratch wear rate and the adhesion between PEEK coatings and substrate decreased with increasing h-BN content. The poor adhesion resulted from the reductions of flow-ability and viscosity between PEEK and substrate caused by heat dissipation from the h-BN particles.

Abstract: A combined processing scheme is used to develop polyurethane (PU) coatings with a nanoclay in three different weight percentages (1, 3 and 5 wt %). TEM of polymer-nanoclay suspensions shows exfoliation, intercalation and even agglomeration of clay layers. XrD studies also indicate expansion in gallery spacing of nanoclay layers in PU coatings. Improvement in scratch and mar resistance occurs, although the gloss values are reduced to some extent. Coating properties show improvement with addition of less than 3wt% clays.

Abstract: TiN protective coating was prepared on NdFeB by DC magnetron sputtering to improve the corrosion resistance and scratch resistance of the magnetic. During deposition, the nitrogen/argon mixture gas was introduced into the chamber with the nitrogen partial pressure at 20 % and 10 % and the bias of 200 V was applied to subtract, respectively. At a lower nitrogen partial pressure of 10%, TiN coating was composed of many particles with an irregular shape. With increasing the nitrogen pressure to 20%, composing particles become small and show as the regular trihedron shape. All TiN coatings have a cubic structure. The bias makes the depositing TiN coating denser and preferential growth become no obvious. By the nitrogen partial pressure of 20 % and bias of 200 V, the dense TiN coating has best corrosion resistance and excellent wear resistance.

Abstract: To improve scratch-resistance and abrasion-resistance of water-based varnish, change the type of water-based resin, the type and content of wax emulsion and flow agent, then test scratch-resistance and abrasion-resistance of water-based varnish. The results show that resin and wax emulsion has a great influence on the scratch-resistance and abrasion-resistance of water-based varnish. Adding appropriate amount of wax emulsion can improve scratch-resistance and abrasion-resistance to some extent. Adding flow agent has certain influence on scratch-resistance of water-based varnish.