Scratch Test

Abrasive wear is one of the most common types of wear, which makes abrasive wear resistance very important in many industries. The hardfacing is considered as useful and economical way to improve the performance of components submitted to severe abrasive wear conditions, with wide range of applicable filler materials. The abrasive wear resistance of the three different hardfaced coatings (two iron-based and one WC-based), which were intended to be used for reparation of the impact plates of the ventilation mill, was investigated and compared. Abrasive wear tests were carried-out by using the scratch tester under the dry conditions. Three normal loads of 10, 50 and 100 N and the constant sliding speed of 4 mm/s were used. Scratch test was chosen as a relatively easy and quick test method. Wear mechanism analysis showed significant influence of the hardfaced coatings structure, which, along with hardness, has determined coatings abrasive wear resistance.

Titannitrid (TiN) ist ein weithin bekanntes Beschichtungsmaterial für die Verbesserung der tribologischen Eigenschaften von Werkzeugen und Maschinenteilen in industriellen Anwendungen. Im Rahmen dieser Diplomarbeit wurde untersucht, wie sich die Ionenbehandlung mit einer Anode-Layer-Source-Ionenquelle auf die Haftfestigkeit von bei Raumtemperatur gesputterten TiN Schichten auswirkt. Für eine gut haftende Schicht ist die Adhäsion der Schicht auf der Substratoberfläche maßgeblich verantwortlich. Als Substrate wurden unterschiedliche Stähle verwendet. Über die Kontaktwinkelmessung konnte gezeigt werden, dass die Benetzbarkeit von vorbehandelten Proben zunimmt. Bei den Untersuchungen mittels des Scratchtestes konnte gezeigt werden, dass sich bei bestimmten Vorbehandlungsparametern der Anode-Layer-Source Ionenquelle, die Haftung der TiN-Schichten gegenüber unbehandelten Proben verbessert. Es konnte auch gezeigt werden, dass sich mit zunehmendem Chrom Gehalt der Substrate die Haftung verschlechtert.

Abrasive wear resistance is very important in many applications and in most cases it is directly correlated with hardness of materials. Possible solutions for overcoming poor abrasive wear resistance of light metals, like Al-alloys, is using of coatings. In this paper the investigated results of the two types of ferrous-based coatings were presented and compared with gray cast iron, known as a material with good abrasive wear resistance. Process used for coating deposition on an Al-Si alloy substrate was Atmospheric Plasma Spraying (APS). Scratch tests with diamond indenter were used to simulate abrasive wear process. The indenter velocity of 10 mm/min was used over a wear tracks of 10 mm, with different normal loads applied. Both, coefficient of friction and wear rate of the samples were investigated and analysed in correlation with its mechanical properties.

Advanced engineered ceramics such as sapphire are increasingly being used for industrial applications as they are hard, strong, inert, light weight and have great optical and electrical properties. Manufacturing this material without causing surface and subsurface damage is extremely challenging due to their high hardness, brittle characteristics and poor machinability. However, ductile regime machining of these materials is possible due to the high pressure phase transformation (HPPT) occurring in the material caused by the high compressive and shear stresses induced by the single point diamond tool tip. To further augment the ductile response of the machined material, traditional single point scratch tests are coupled with a micro-laser assisted machining (μ-LAM) technique. This paper discusses the effect of laser heating on the ductile response of polycrystalline zinc selenide (ZnSe).

Abrasive wear is one of the most common types of wear, which makes abrasive wear resistance very important in many industries. The hardfacing is considered as useful and economical way to improve the performance of components submitted to severe abrasive wear conditions, with wide range of applicable filler materials. The abrasive wear resistance of the three different hardfaced coatings (two iron-based and one WC-based), which were intended to be used for reparation of the impact plates of the ventilation mill, was investigated and compared. Abrasive wear tests were carried-out by using the scratch tester under the dry conditions. Three normal loads of 10, 50 and 100 N and the constant sliding speed of 4 mm/s were used. Scratch test was chosen as a relatively easy and quick test method. Wear mechanism analysis showed significant influence of the hardfaced coatings structure, which, along with hardness, has determined coatings abrasive wear resistance.

ABSTRACT: The numerical study of the scratch test on glassy polymers needs a well adapted mechanical behaviour law both viscoelastic and viscoplastic. To test different models, an algorithm which allows to as-sembly in series two models has been developped. In our cas, it is used to associate a viscoelastic model with viscoplastic one. The simulations carried out lead to some phenomenological results showing the importance to account for the time dependency of the stiffness modulus.

This paper outlines an experimental study of the TiSiN coatings deposited using a combination of direct current (DC) and radio frequency (RF) PVD magnetron sputtering (DR-PVD) on high speed steel (HSS) substrates. An L 9 Taguchi orthogonal array was used to conduct the experiments for finding the optimum process parameters. Four process parameters, (1) RF power, (2) DC power, (3) nitrogen to argon (N 2/Ar) gas ratio and (4) deposition time were considered. The surface structure and composition of selected coating samples were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The critical load in the micro-scratch test was used as a measure of scratch adhesion. Investigations of the scratch tracks were viewed by an optical microscope. The results showed that higher scratch adhesion strength was achieved using RF power of 100W, DC power of 500W, N 2/Ar ratio of 1:2.5 and a deposition time of 6h. Optimization resulted in an increase of the critical load value from 827mN to 1371mN, signifying an improvement of over 65%. © 2011 Elsevier B.V.

http://ac.els-cdn.com/S0257897211007407/1-s2.0-S0257897211007407-main.pdf?_tid=4890d096-a9c7-11e3-9909-00000aab0f02&acdnat=1394616093_08c5034897488fdec859aedf0ed896be 
www.sciencedirect.com/science/article/pii/S0257897211007407

Abstract This paper presents the results of research into the influence of surface modification of 7075 aluminum alloy with nitrogen ions on the type and quantity of chemical bonds and on the mechanical properties of Si:C:N:H coatings deposited with use of the Micro Wave Chemical Vapor Deposition method. Fourier Transform Infrared Spectroscopy results show that during coating deposition the following chemical bonds are mainly formed: CH 2 in Si CH 2 Si , C C , NH , NH 2 , CH 3 , and CH 2 . Their relative proportions are directly linked to the hardness and modulus distribution of the coatings. The modification of Al alloy substrate with N + ions below 670 K promotes an increase (by a factor of 2) in the formation of NH and NH 2 groups relative to C C double bonds and the CH 2 group in the Si CH 2 Si chain as compared to unmodified samples. However, above 670 K the mechanism changes whereby more C C and Si CH 2 Si groups are formed as compared to CH 2 , CH 3 , NH , and NH 2 groups. The change of mechanism determines the hardness of the coatings, which is approximately 8 GPa in the case of modification above 670 K, but does not exceed 3 GPa if modification was conducted below 670 K. Still, coatings deposited on substrates modified above 670 K delaminate in scratch tests by propagation of cracks within the scratch track. This behavior is not observed for coatings deposited below 670 K (on nitrogen-modified substrates). In this case, only plastic deformation in the sample/indenter contact region is present.

Calcium phosphate (CaP) compounds like hydroxyapatite and tricalcium phosphates are considered to be very important biomaterials. This study used RF-magnetron sputtering (RF-MS) to deposit CaP onto 316L SS. Due to the complex nature of the effect of different sputtering parameters on the quality and integrity of the coatings, there is a need to further investigate those parameters collectively. An L 9(3 4) orthogonal array was employed to design the experiment that was used to investigate four important coating parameters which include RF-power, argon gas flow rate, deposition time and post-heat treatment conditions. The coating composition and structure were evaluated using XRD, EDX and FTIR. The mechanical property was measured in terms of the adhesion strength using a microscratch testing machine. The response graph of the results revealed that the interfacial strength of CaP was mainly influenced by the deposition power, while the coating thickness was predominantly affected by the argon gas flow rate. High adhesion strength was achieved when the coatings have at least 2 μm thickness and deposited at a working pressure of 12 m Torr. ANOVA on the control factors helped rank the parameters accordingly in order of importance. Based on the response of the control factors, it was found that optimum adhesion strength could be achieved by depositing the coatings using the following parameters: 10 sccm of argon gas flow rate; 150 W of RF power; and 16 h of deposition.

http://www.worldscientific.com/doi/abs/10.1142/S021797920905479X

The improved scratch resistance of epoxy-based coatings on titanium alloy is greatly needed in the current biomedical device sector. Due to commercial factors, this improvement must be either non-consumptive or inherited from the antecedent machining steps. This study contributes an extensive understanding of Ti-6Al-4 V surface topography, microstructure, chemistry and wettability generated with various processes, such as milling, polishing, hydrofluoric acid-etching and micro-blasting with different process parameters by utilizing optical and electron microscopy, energy-dispersive X-ray spectroscopy, X-Ray diffraction and surface tension. The phenolic resin is then spin-coated, cured and scratched with a conical indenter in a constant loading mode. The influence of roughness parameters, microstructural and chemical changes on wettability and delamination size, pattern and mode are analyzed. The root mean square gradient of surface slope and the developed interfacial area ratio are found to be in good correlation with the delamination factor. The delamination factor and specific traction force after micro-blasting are improved by a factor of two compared to that achieved by polishing or milling and is superior to that obtained by acid-etching. This study, therefore, clearly demonstrates the strong potential of micro-blasting as a pretreatment technique to enhance the adhesion strength and scratch-resistance of epoxy coating on titanium implants.