Papers by Keyword: Hardness

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Authors: Yu Mei Dai, Yong Qing Ma, Yan Bin Wu, Ya Nan Ji
Abstract: 6CrW2MoVSi steel has a refined and even microstructure after heat treatment, the average size of annealing carbide is 0.6 μm; quenching martensite is mainly lath-shaped martensite and only a small amount of acicular martensite, and the size of quenching acicular at 950 °C is smaller than 2.5 μm. The curve of quenching hardness increasing with quenching temperature rising is divided into three sections. In the middle section of quenching between 910 °C ~ 980 °C, quenching hardness presents slow rising trend. After higher temperature quenching, there are low and high temperature tempering precipitation hardening zones. At 220 °C ~ 240 °C tempering temperature, precipitation hardness is HRC54 ~ 58. At 540 °C ~ 570 °C tempering temperature, precipitation hardness is HRC52 ~ 56.
Authors: Tien Li Chen, Ho Chang, Wei Hao Wong
Abstract: This study adds nanopowder, such as ZnO and TiO2, in different concentrations to water-based woodenware coating, and explores the properties of the coating on the woodenwares. After the coating has been applied to the testing materials, the thickness and lightness are measured. These values are compared to the properties of the water-based woodenware coating with nanopowder of specific concentration, such as hardness, lightness and adhesion. According to the results of the experiments, adding TiO2 nanopowder to the AE-418 water-soluble polyurethane coating helps to increase the hardness of the coating. The amount added is positively related to the hardness of the coating; the result is the opposite with the WP-1715 water-soluble acrylic resin coating. After adding powder such as TiO2 or ZnO to the AE-418 water-soluble polyurethane coating, the lightness of the coating becomes lower. However, powder with higher concentration leads to higher lightness. In addition, the adhesion of the coating is stronger when nanopowder of higher concentration is added.
Authors: Yu Zhang, Zi Jian Wang, Yi Lin Wang, Zhi Jian Zhang, Yi Sheng Zhang
Abstract: Magnetic nondestructive testing methods including eddy current testing, magnetic memory, magnetic Barkhausen noise and so on are widely used in testing mechanical properties of ferromagnetic parts. Experiments were done to study the relationship between hardness and magnetic properties of ultra-high strength steel (UHSS), which plays an important role in automobile industry. The magnetic properties of UHSS specimens with different hardness were studied. The result shows that there is a strong connection between hardness and magnetic properties. Coercive force of UHSS is proportional to the hardness. This can be used to explain certain mechanism of magnetic nondestructive testing method such as connection between hardness and Barkhausen noise.
Authors: I.V. Osetkovskiy, N.A. Kozyrev, R.E. Kryukov
Abstract: In the article is shown the comparative analysis between structures of surfaced by the flux coded wire metal systems Fe-C-Si-Mn-Cr-Ni-Mo-V and Fe-C-Si-Mn-Ni-Mo-W-V. These powder wires are supposed to be used in recovering details and equipment components and machines, that works in conditions of intensive abrasive – shock wear. Manufacturing and surfacing of flux cored wires samples were made in laboratory conditions. Defined chemical composition of the surfaced metal. Deposited metal samples hardness and wear resistance were researched. In the course of deposited meta surface metallographic analysis were made following metallographic researches: defined nature and level of nonmetallic oxides impurity, type and morphology of the microstructure, grain size of surfaced samples. Estimation of the chemical composition components influence on the hardness and wear resistance were obtained.
Authors: Z.M. El-Baradie, O.A. El-Shahat, V. Orlov
Authors: P. Hidalgo, C.M. Cepeda-Jiménez, O.A. Ruano, F. Carreño
Abstract: The 7075 Al alloy was processed by accumulative roll bonding (ARB) at 300, 350 and 400 °C. The microstructure and texture were characterized and the hardness was measured. Cell/(sub)grain sizes less than 500 nm and typical β-fibre rolling texture were observed in the three ARBed samples. At 400 °C, the presence of elements in solid solution leads to a poorly misoriented microstructure and to a homogeneous β-fibre texture. At 300 and 350 °C highly misoriented microstructure and heterogeneous β-fibre rolling texture are observed, especially at 350 °C, wherein the degree of dynamic recovery is higher. Hardness of the ARBed samples is affected by the amount of atoms in solid solution at the different processing temperatures.
Authors: Jan Brüninghaus, Anna Oster, Bernd Kuhlenkötter
Abstract: In incremental sheet forming the material properties change dependent on the wall angle. In addition to sheet thinning, material hardening can be observed and for stainless steel the formation of strain induced martensite has been reported. These process characteristics have been extensively examined for the forming of parts in one step. In this study, a first investigation is made to control the material properties independent on the wall angle by a multi-step expanding approach. For this, in the first step a steep wall angle is formed and in the following steps this region is transformed to a shallow wall angle, keeping the material properties. To demonstrate and verify this new approach a small cone frustum with a wall angle of 60° was formed as a preform. This cone frustum was repeatedly expanded in steps of 2° to get finally a cone frustum with 30° wall angle. The stepwise expanding causes a considerably growing of the shape in depth direction, especially at the preformed area. By a heuristic approach the geometric accuracy of the final cone was optimized. The microhardness measurement of the formed cones shows that the final cone frustum has a region, where the material properties are similar to the first formed 60° wall angle. By this new approach the possibility to influence the material properties of the final part purely by tool path is demonstrated. In particular it is possible to form regions with shallow wall angles that have the material properties of regions with steep wall angles.
Authors: Ben Jackson, Rob Torrens, Leandro Bolzoni, Fei Yang, Mike Fry, Aamir Mukhtar
Abstract: Titanium alloy composites with titanium boride (TiB) discontinuous reinforcement have shown improved performance in terms of strength, stiffness, and hardness. Producing this composite through selective laser melting (SLM) can combine the advantages of freeform design with the ability to produce TiB reinforcement in-situ. In this study, SLM was used to consolidate a pre-alloyed Ti-6Al-4V (Ti64) and amorphous boron (B) powder mixture with the intent of producing 1.5wt% TiB reinforcement in a Ti64 matrix. The processing parameters of laser power and scanning speed were investigated for their effect on the density, microstructures, and hardness of the composite material. The results showed that the boron and Ti64 composite could achieve a density greater than 99.4%. Furthermore, it was found that processing parameters changed the microstructural features of the material. The higher the energy density employed the more homogenous the distribution of boron modified material. Macro features were also observed with laser paths being clearly evident in the subsurface microstructure. Micro-hardness testing and density measurement also showed a corresponding increase with increasing energy density. Maximum hardness of 392.4HV was achieved in the composite compared to 354.2HV in SLM fabricated Ti64.
Authors: Su Yu Wang, Wen Jie Yang, Lin Lin Ma
Abstract: Work hardening reserches in metal cutting has an important significance in improving surface quality of the workpiece and the service performance of parts. The paper introduces current researches of the work hardening in metal cutting process, analyses the forming mechanism and influencing factors of the work hardening and discusses the effects of the work hardening on workpiece service performance. At last, the new trends of work hardening researches in metal cutting process are conclusively predicted.
Authors: Li Jun Yang, Yang Wang
Abstract: Laser forming of metal sheet is a forming technology of sheet without a die that the sheet is deformed by internal thermal stress induced by partially irradiation of a laser beam. In this paper, the bending behavior of common stainless steel 1Cr18Ni9 sheet is studied after being irradiated by straight line with a Nd:YAG pulsed laser beam. The aim of the investigation is to find out the relationship of the physical behaviors of heat affected zone (HAZ) with the pulse parameters of the laser. Through the analysis of the fundamental theory of pulsed laser affected, this paper shows the affected characteristics of metal sheet with pulsed laser forming. The results show that the microstructure of HAZ of pulsed laser scanned is layered, and the micro-hardness is improved than that in matrix. The microstructures show that the deformed grain structure is inhomogeneous, that caused the grain sizes and grain orientations in HAZ to become different. By qualitative analysis of experimental result, the conclusion obtained may provide basis for theoretical investigation and possible industrial application of laser forming process in the future.
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