Papers by Keyword: Hardness

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Authors: Kamil Kolařík, Karel Trojan, Jiří Čapek, Jiří Sís, Ondřej Řídký, Lukáš Zuzánek, Nikolaj Ganev
Abstract: Residual stresses (RS) and welding process represent a traditional partnership between an ever evolving, and vital, technological process and a quantity characterizing the result of this process. As the modern way of joining materials is shifting gradually from conventional welding into friction stir or laser welding, RS remain a crucial parameter which gives clues about the welds’ behavior under dynamic loads. In this contribution the joint created by laser welding with filler wire is described by 2D maps of RS and hardness.
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Authors: Christopher Locke, G. Kravchenko, P. Waters, J. D. Reddy, K. Du, A.A. Volinsky, Christopher L. Frewin, Stephen E. Saddow
Abstract: Single crystal 3C-SiC films were grown on (100) and (111) Si substrate orientations in order to study the resulting mechanical properties of this material. In addition, poly-crystalline 3C-SiC was also grown on (100)Si so that a comparison with monocrystaline 3C-SiC, also grown on (100)Si, could be made. The mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates were measured by means of nanoindentation using a Berkovich diamond tip. These results indicate that polycrystalline SiC thin films are attractive for MEMS applications when compared with the single crystal 3C-SiC, which is promising since growing single crystal 3C-SiC films is more challenging. MEMS cantilevers and membranes fabricated from a 2 µm thick single crystal 3C-SiC grown on (100)Si under similar conditions resulted in a small degree of bow with only 9 µm of deflection for a cantilever of 700 µm length with an estimated tensile film stress of 300 MPa. Single crystal 3C-SiC films on (111)Si substrates have the highest elastic and plastic properties, although due to high residual stress they tend to crack and delaminate.
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Authors: Mahmoud Mostafavi, Yelena Vertyagina, Christina Reinhard, Robert Bradley, Xia Jiang, Marina Galano, James Marrow
Abstract: Hardness testing obtains material properties from small specimens via measurement of load-displacement response to an imposed indentation; it is a surface characterisation technique so, except in optically transparent materials, there is no direct observation of the assumed damage and deformation processes within the material. Three-dimensional digital image correlation (digital volume correlation) is applied to study deformation beneath indentations, mapping the relative displacements between high-resolution synchrotron X-ray computed tomographs (0.9 μm voxel size). Two classes of material are examined: ductile aluminium-silicon carbide composite (Al-SiC) and brittle alumina (Al2O3). The measured displacements for Hertzian indentation in Al-SiC are in good agreement with an elastic-plastic finite element simulation. In alumina, radial cracking is observed beneath a Vickers indentation and the crack opening displacements are measured, in situ under load, for the first time. Potential applications are discussed of this characterization technique, which does not require resolution of microstructural features.
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Authors: Hideki Shimizu, S. Kiyono, Wei Gao, H. Shoji
Abstract: For effective medical treatment, sensors that can find foreign bodies such as tumors in early stage are required. This paper describes a new sensor for foreign body detection utilizing the fact that the property hardness of foreign bodies differs from that of normal tissues. It consists of a balloon probe, which is constructed with a thin rubber membrane inflated with compressed air, and an optical deformation analyzing system. Experiments are carried out using samples in which single hard balls are embedded to model single tumor in soft tissue. It was confirmed that this sensor can detect the existence of the hard ball and can also distinguish the inequality of size and hardness of the ball. Furthermore, experimental results detecting multi-objects showed that this sensor has the ability to detect the existence of multi objects and their relative positions simultaneously. By measuring the consistence of the arm and the abdomen of human body, it is proved that the sensor is also suitable for consistence measurement of human anatomy.
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Authors: Supakanya Khanchaiyaphum, Charnnarong Saikaew, Parinya Srisattayakul, Naphatara Intanon
Abstract: Improving the surface quality of various machine components can extend their lifespans by several orders of magnitude. Thin film coating is one approach that can be used to enhance machine part surface quality. In this work, three different thin film coatings (i.e, CrN, CrC and Cr-C-N) were statistically compared for surface quality improvement of fishing-net weaving machine component, namely an upper hook. All coatings were deposited utilizing DC sputtering technique. The effects of coating types on hardness for both hardchrome and non hardchrome coated upper hooks were systematically investigated using one-way analysis of variance (ANOVA). Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) were used to examine the surface quality of the machine component. This study found that CrN gave very high hardness values of 13.042 GPa for hardchrome coated upper hooks and 12.583 GPa for non-hardchrome coated upper hooks. However, the averages hardness of the hardchrome coated and non-hardchrome coated upper hooks were not significantly different at the 95% confidence level.
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Authors: Norbert Kazamer, Dragos Toader Pascal, Gabriela Marginean, Viorel Aurel Şerban, Cosmin Codrean, Ion Dragoş Uţu
Abstract: In order to be competitive, it is demanded to have thin, tough and long lasting coatings. An important aspect is to use stable deposition technologies. As Cr assures wear, corrosion and high temperature resistance, the most employed coatings in industry generally contain Cr. Nevertheless, Cr is a hazardous element for the humans’ health, therefore, sustainable alternatives are needed to be implemented. The aim of this work is to investigate the microstructure, hardness, corrosion resistance and wear behavior of the novel WC-CoMo compared to conventional WC-Co coatings. So far, WC-CoMo coatings are not part of state of the art regarding the Atmospheric Plasma Sprayed (APS) coatings. WC-Co powder in plain form and mechanically mixed with Mo was deposited using the APS method on standardized Type A Almen Strips (C67 steel). The size of the powder grains varies between 5 µm and 30 µm. The obtained samples were investigated by means of Scanning Electron Microscopy, Energy Dispersive X-Ray Spectroscopy, X-Ray Diffraction, and hardness, wear and corrosion behavior were also evaluated. Results revealed formation of different intermetallic phases around the WC particles, which have a benefic influence on the coating characteristics and microstructure.
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Authors: N. Donnelly, M. McConnell, Denis P. Dowling, J.D. O'Mahony
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Authors: Min Woo Park, Wang Woo Lee, Jae Gab Lee, Chong Mu Lee
Abstract: Chromium (Cr) films were deposited on plain carbon steel sheets by DC and RF magnetron sputtering as well as by electroplating. Effects of DC or RF sputtering power on the deposition rate and properties such as hardness and surface roughness of the Cr films were investigated. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microcopy (SEM) analyses were performed to investigate the crystal structure, surface roughness, thickness of the Cr films. The deposition rate, hardness and surface roughness of the Cr film deposited by either DC or RF sputtering increase with the increase of sputtering power. The deposition rate and hardness of the Cr film deposited by DC sputtering are higher than those of the Cr film deposited by RF sputtering, but RF sputtering offers smoother surface. The sputter-deposited Cr film is harder and has a smoother surface than the electroplated one.
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Authors: Wei Qiang Hu, Zong De Liu, Guang Yang, Yong Tian Wang, Hua Lei Zhang
Abstract: A thick Fe-based amorphous and nanocrystalline composite coating was prepared by in-situ tungsten inert gas (TIG) cladding method. The results show that the cladding coating mainly consists of amorphous phase and nanocrystalline grains. The microstructure study shows that the Fe-based composite coatings have unique microstructure including nano-sized grains surrounded by nano-scale amorphous shell layer (encapsulated structure) and the homogeneously distributed dendrites/cellular crystals. The unique microstructure gives rise to the superior micro-hardness and wear resistance of the coating. The Fe-based coatings have great potential as promising wear-resistance structural materials used in electric power and cement industry.
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Authors: Tian Bo Yu, Niels Hansen
Abstract: A model is suggested to analyze recovery kinetics of heavily deformed aluminum. The model is based on the hardness of isothermal annealed samples before recrystallization takes place, and it can be extrapolated to longer annealing times to factor out the recrystallization component of the hardness for conditions where recovery and recrystallization overlap. The model is applied to the isothermal recovery at temperatures between 140 and 220°C of commercial purity aluminum deformed to true strain 5.5. EBSD measurements have been carried out to detect the onset of discontinuous recrystallization. Furthermore, comparison between the present model and a similar recently developed recovery model is made, and the result is discussed.
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