Papers by Keyword: Scratch Test

Abstract: Abstract. In the present work several films of Ti, TiN, and TiCrN have been coated on AISI 316L stainless steel substrates using magnetron sputtering techniques, in order to improve their surface properties. The morphology and structure of the coatings were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical performances skills in an SBF solution and the adhesion of these deposits were studied to understand these behaviors. From the results it was shown the TiCrN deposition presents the lowest corrosion resistance in the SBF solution, while TiN deposit is the most resistant to corrosion resistance in the same solutions, but its critical load (Lc3-TiN), is relatively low and has a risk of delamination which can limit its use. On the other hand, the Ti deposit exhibits a high resistance to corrosion and a high passivation (i_corr (Ti) = 0.57 µA.cm^-2 and Rp (Ti) = 67.98 KW.cm²). The critical load (Lc3-Ti = 43.38 N), the crack propagation resistance (CPRs-Ti = 81.64 N) and the scratch hardness (HSL-Ti = 125.75´10¹² Pa) also testify to its high adhesion to the AISI 316L substrate. Thus the Ti deposit has proved to be the most favorable protective coating for AISI 316L stainless steel in SBF solution.

Abstract: Hafnium oxide (HfO₂) is a material characterized by a good mechanical, thermal and chemical stability and is used as a material in a variety of technological applications in optics and electronics. In this work the influence of annealing temperature on the mechanical structural properties of amorphous HfO₂ thin film was explored. Films were deposited by electron beam evaporation and annealed in the temperature range from 200 °C to 500 °C in vacuum. Mechanical properties such as hardness and elastic modulus were determined using nanoindentation, while cohesive-adhesive properties of the film using a scratch test. Surface morphology was determined using a confocal microscope and structure using XRD. The transformation of amorphous phase of the films to the nanocrystalline monoclinic phase was observed after vacuum annealing at 500 °C. This crystallization leads to increase in hardness on one hand but also to growth of brittleness and in turn to decrease in scratch resistance on the other hand.

Abstract: Biodegradable materials are a further development of new medical applications, such as orthopedic implants and vascular stents, or the tissue scaffold. The variety of alloying elements introduced into magnesium alloys lead to superior corrosion resistance and mechanical properties similar to the biological bone. From a mechanical point of view, increasing the percentage of calcium leads to decreased strength and elongation resistance, and Yttrium addition greatly improves tensile strength and favors a slower degradation process. Three different Mg-0.5Ca-xY alloys were obtained, varying the concentration of the Y-element. The Mg-0.5Ca-xY system was tested from the point of view of micro-scratch and micro-indentation with three determinations each, obtaining results for Young's mode, micro-hardness, COF and stiffness. These alloys possess mechanical properties for use as orthopaedic applications. As future studies, mechanical properties can be improved by performing heat treatments.

Abstract: Surface modifications have been progressively applied in order to improve the mechanical, biological and chemical properties of metallic dental and orthopedic implants. Therefore, the novel and multifunctional biocomposites coating matrices, which also consist of local and targeted drug delivery systems, are the most recent applications in the medical field. In this study, gentamicin antibiotic containing HAp bioceramics were utilized in a biodegradable poly-lactic acid thin film matrix which was applied to Ti6Al4V metallic implant surfaces. nanoindentation and scratch test methods were applied. It was observed that, bonding between coating and the substrate is strong enough to be used in implant applications. Additionally, it was observed that the hardness and young modulus values of uncoated Ti6Al4V disc which were 4.3 and 125.2 GPa, respectively. However, under the same testing conditions, it was also observed that the H values (0.6-0.8GPa) and the E (50-60 GPa) values of PLA-HAp biocomposite coated samples are slightly higher than the H values (0.4-0.6 GPa) and the E values (40-50GPa) of only PLA coated sample.

Abstract: Hot gas welding has been used in the process of polypropylene (PP) welding in many applications. It was appropriate for various multipart productions such as plastic constructions, automotive parts, tanks and pipeline. However, the surface properties of welded areas were varied particularly at each zone and thus affected numerous scratch resistances. The microstructure of scratch trace, hardness and scratch wear rate were studied by scanning electron microscope, hardness tester and scratch tester, respectively. From the results, it was found that the deformation of PP was induced with welding process. The scratch trace was showed that it related with decreasing of hardness properties.

Abstract: The tribological properties of magnetron sputtered amorphous silicon carbide (a-SiC) and silicon carbonitride coatings (a-SiCN) with thickness of 2.2 and 3.4 µm were investigated. Samples were additionally annealed at temperature of 700°C or 900°C in air. Progressive load scratch tests were performed on the annealed samples as well as on the as deposited ones. An acoustic emission signal was detected during all tests using the sample holder with embedded sensor of our own design. Results indicate no change in wear resistance of SiCN sample after high temperature exposure up to 900°C, unlike in the tests of SiC coatings. Detection of acoustic emission generated during the scratch test proved to be a significant improvement for the coating evaluation.

Abstract: Diamond impregnated tools are commonly used for the machining of concrete and rocks, e.g. sawblades or core drills. These tools consist of a metal bond and randomly distributed diamonds. The grinding of inhomogeneous materials like concrete is a complex system which is interfered by a large number of influencing factors. Although simple models exist describing the material removal processes, there is still a lack of knowledge concerning the fundamental mechanisms during grinding. Thus, the optimisation and development of diamond tools are mainly based on experience and empirical methods. Concrete is described as a compound material which exhibits different phases of minerals like cement and aggregate phases. In reinforced concrete, steel is a further phase which has got highly different properties in comparison to the mineral phases. The detailed analysis of the material removal mechanisms is difficult because of the random phase composition of concrete and the random diamond distribution within the tools as well. But, the knowledge of the material removal mechanisms are of vital interest for the development of efficient tools. A fundamental understanding of material removal processes and wear mechanisms can be drawn from single grain scratch tests. Recent developments in diamond tool manufacturing provide the defined positioning of diamond grains in the tool body. This offers new possibilities based on scratch tests regarding tool development. Thus, scratch tests on concrete and reinforced concrete were conducted using single grain diamond tools. First basic understanding was achieved by scratch tests with diamond indenters by varying feed speed and analysing the resulting forces. Detailed investigations were accomplished by installing a tribometer within a scanning electron microscope (SEM). This setup allowed the analysis of the development of the resulting scratch groove.

Abstract: The scratch test is a well-established instrumental method for assessment of the cohesive-adhesive parameters of thin films and coatings. Its evaluation is classically performed using the microscopic analysis of residual scratch and the indenter depth-change record. However, these analysis methods can be insufficient for detection of the very first film-to-substrate adhesion failures. To overcome this difficulty, an independent method of detection of acoustic emission signals can be employed. The detection system of acoustic emission, developed in our laboratory, utilizes a special holder and continuous recording during the whole scratch test. The piezoelectric sensor with 2 MHz sampling rate and sophisticated software allow a thorough post-process analysis of recorded acoustic emission signal. Failure events can be observed on microsecond scale and their frequency spectra can be evaluated.The demonstration of the acoustic emission probe detection capability is performed on the model layers. Comparison of the acoustic emission record to residual scratch image and indenter depth-change record shows a detection sensitivity of the method. Analysis of failure mode dynamics at the appropriate time scale is outlined.

Abstract: In this study, the (Fe,Cr)₇C₃ particles strengthened gradient composite was produced by in situ synthesis process with subsequent heat treatment from gray cast iron (HT300) and high purity chrome plate. The microstructure, phase composition and wear resistance of the composite were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and scratch tester. The results showed that the thickness of the gradient layer was about 758 μm after heat treatment at 900 °Cfor 4 h. And it can be divided into three areas depending on microstructure. The outermost layer which was ~60 μm of thickness, was the dense ceramic layer with high volume fraction of (Fe,Cr)₇C₃ ~90%. No obvious grain boundaries were observed. The subsurface layer was the particles dispersed layer, which was ~525 μm of thickness, with the volume fraction of (Fe,Cr)₇C₃ decreased to 70%. The lowermost layer was ferrite, with about 173 μm thickness. A good metallurgical bond generated between the composite layer and matrix. The depth and the width of surface scratch increased with the raising loads from 0 to 100 N, and the cracks mainly included micro-crack, tiny dens crack, mixture crack and through-wall crack. The (Fe,Cr)₇C₃ particles were broken and scraped when the load exceeded 80 N.

Abstract: Scratch test is one of widely used, fast, and effective methods to obtain the critical loads that are related to adhesion properties of coatings. The determination of adhesion and the scratch resistance is essential for the mechanical characterization of surface layers for research and industry. To evaluate the performance of coatings the scratch test with a Rockwell-C diamond stylus as indenter is a commonly used test for the characterization of hard coatings on predominant metallic substrates due to its comparatively robust experimental setup, the easy use and the representative results. This is the only technique capable of imaging such interface defects which are due to the stressin duced by the scratch experiment.This paper aims to characterize the adhesion and scratch resistance using Millennium200 - Technical Tribo equipment of Ti layer deposited on steel surfaces by means of TIG/WIG welding technique. Ensuring appropriate functional properties of WIG welding coatings (Ti) requires a good compatibility with the substrate material (S235). For this reason was used to deposit titanium WIG welding an intermediary layer of copper, obtained in the same experimental conditions. The optimal selection of the coating material takes into consideration the metallurgical, mechanical and process technology compatibility. The mechanical properties of coatings must match the substrate. From this point of view, maintaining a high corrosion resistance is mainly conditioned by achieving a good adhesion and a microstructure free of internal cracks or other defects.