| 21. |
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| 22. |
- Heinrichs, Jannica, 1982-, et al.
(författare)
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On the deformation mechanisms of cemented carbide in rock drilling : Fundamental studies involving sliding contact against a rock crystal tip
- 2018
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Ingår i: International journal of refractory metals & hard materials. - : Elsevier. - 0263-4368. ; 77, s. 141-151
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Tidskriftsartikel (refereegranskat)abstract
- Cemented carbide is a composite material, most commonly consisting of tungsten carbide grains in a metallic matrix of cobalt. The combination of a hard ceramic phase in a ductile metallic matrix combines high hardness and ability to withstand plastic deformation with toughness to avoid cracking and fracturing. Since these properties are very important in rock drilling, cemented carbides are frequently used in such applications. In earlier work, it was found that granite in sliding contact with considerably harder cemented carbides not only results in plastic deformation of the cemented carbide composite, but also in plastic deformation of some of the individual WC grains. The latter observation is remarkable, since even the two hardest granite constituents (quartz and feldspar) are significantly softer than the WC grains. This tendency to plastic deformation of the WC grains was found to increase with increasing WC grain size. The present investigation aims to increase the understanding of plastic deformation of cemented carbides in general, and the individual WC grains in particular, in a situation representative for the rock drilling application. The emphasis is put on explaining the seemingly paradoxical fact that a nominally softer counter material is able to plastically deform a harder constituent in a composite material. The experimental work is based on a scratch test set-up, where a rock crystal tip slides against a fine polished cemented carbide surface under well-controlled contact conditions. The deformation and wear mechanisms of the cemented carbide are evaluated on the sub-micrometer scale; using high resolution FEG-SEM, EDS, EBSD, BIB and FIB cross-sectioning. The size of the Co-pockets, together with the shape and size of WC grains, turned out to be decisive factors in determining the degree of carbide deformation. The results are discussed with respect to their industrial importance, including rock drilling.
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| 23. |
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| 24. |
- Heinrichs, Jannica, et al.
(författare)
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Surface degradation of cemented carbides in scratching contact with granite and diamond : the roles of microstructure and composition
- 2015
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 342, s. 210-221
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Tidskriftsartikel (refereegranskat)abstract
- Cemented carbides are composite materials comprising metal carbide grains in a more ductile metallic binder. This microstructure results in a combination of high hardness and toughness, making them commonly used as rock crushing parts in rock drilling, where they usually show wear on a very fine scale. The hardness and toughness can ultimately be tuned for the application by adjusting the carbide grain size, binder fraction and composition.In the present investigation, the initial micro-scale deformation and wear of polished cemented carbide surfaces is studied by micro scratching with diamond and granite styli, and also by instrumented micro and nanoindentation. The deformation and wear is evaluated on the sub-micrometer scale using high resolution FEG-SEM and FIB cross sectioning. The selected microstructures include besides four cemented carbide grades that are commonly used in rock drilling also binderless and Ni containing grades. This wider range of cemented carbides is used to gain fundamental insights into the relations between microstructure and micro-scale deformation and wear. The results are discussed with respect to their significance for wear of cemented carbides in rock drilling operations.
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| 25. |
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| 26. |
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| 27. |
- Jayamani, Jayaraj, et al.
(författare)
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Electrochemical and passivation behavior of a corrosion-resistant WC-Ni (W) cemented carbide in synthetic mine water
- 2023
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Ingår i: International journal of refractory metals & hard materials. - : Elsevier BV. - 0263-4368. ; 114
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Tidskriftsartikel (refereegranskat)abstract
- Two different grades, WC-20 vol.% Ni and WC-20 vol.% Co cemented carbides, respectively were systematically investigated concerning their microstructure, binder composition, and corrosion behavior. SEM-EBSD analysis verified that both grades have similar WC grain sizes (0.9-1.1 mu m). AES analysis confirmed that the binder phase of the respective grade is an alloy of Ni-W and Co-W and that the concentration of W in the Ni-and Co-binder is 21 and 10 at. %, respectively. In synthetic mine water (SMW), the EIS behavior of WC-Ni(W) at the open circuit potential (OCP) conditions was studied for different exposure periods (up to 120 h). The EIS data fitting estimates low capacitance and high charge transfer resistance (Rct) values, which indicate that the passive film formed on WC-Ni(W) is thin and exhibits high corrosion resistance. At the OCP and potentiostatic-passive conditions, SEM investigations confirm the uncorroded microstructure of the WC-Ni(W). The AR-XPS studies confirmed the formation of an extremely thin (0.25 nm) WO3 passive film is responsible for the high corrosion resistance of WC-Ni(W), at OCP conditions. However, above the transpassive potential, the microstructure instability of WC-Ni(W) was observed, i.e., corroded morphology of both WC grains and Ni(W) binder. The electrochemical parameters, Rct, corrosion current density, and charge density values, confirmed that the WC-Ni(W) is a far better alternative than the WC-Co(W) for application in SMW.
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| 28. |
- Lindgren, Lars-Erik, et al.
(författare)
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Simulation of hydroforming of steel tube made of metastable stainless steel
- 2010
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Ingår i: International journal of plasticity. - : Elsevier BV. - 0749-6419 .- 1879-2154. ; 26:11, s. 1576-1590
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Tidskriftsartikel (refereegranskat)abstract
- The Olson-Cohen model for strain induced deformation, further developed by Stringfellow and others, has been calibrated together with a flow stress model for the plastic deformation of metastable stainless steel. Special validation tests for checking one of the limitations of the model have also been carried out. The model has been implemented into a commercial finite element code using a staggered approach for integrating the stress-strain relations with the microstructure model. Results from a thermo-mechanical coupled simulation of hydroforming of a tube have been compared with corresponding experiments. The agreement between experimental results of radial expansion and martensite fraction and the corresponding computed results is good.
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| 29. |
- Mahade, Satyapal, 1987-, et al.
(författare)
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Novel wear resistant carbide-laden coatings deposited by powder-suspension hybrid plasma spray : Characterization and testing
- 2020
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 399
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Tidskriftsartikel (refereegranskat)abstract
- Thermal spraying with a hybrid powder-suspension feedstock presents a novel approach to conveniently realize coatings with unusual chemistries and unique microstructures. In this study, coatings were deposited by simultaneous spraying of T-400 (Tribaloy-400) powder and Cr3C2 suspension with varying relative feed rates. For comparison, pure T-400 coating was also deposited using powder feedstock via atmospheric plasma spray (APS) route to assess the role of incorporating a hard, finely distributed carbide phase in the coating. SEM (Scanning electron microscopy)/EDS (Energy-dispersive X-ray spectroscopy) investigation of the hybrid coatings revealed a lamellar microstructure with distributed fine carbides. XRD (X-ray diffraction) analysis of the feedstock and hybrid coatings showed the presence of original feedstock constituents, along with some oxides of chromium, in the deposited coating. Hardness measurements on the as-sprayed coatings indicated higher hardness in hybrid coatings than in the pure T-400 coating. The deposited coatings were subjected to scratch testing on polished surfaces as well as on polished cross sections. The scratching response of the coatings was examined by SEM analysis. Results demonstrated that the hybrid coatings possess excellent scratch resistance, superior compared to the pure T-400 coating, which is promising for extending the durability of engineering components operating under severe wear conditions. This was confirmed by abrasion test results which established the superior wear resistance of hybrid coatings. The above hybrid approach is easily extendable to other material systems and can have important implications in the realization of next-generation wear resistant coatings. © 2020 Elsevier B.V.
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| 30. |
- Nilsson, Maria, et al.
(författare)
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An investigation of worn work roll materials used in the finishing stands of the hot strip mill for steel rolling
- 2013
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Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : Sage Publications. - 1350-6501 .- 2041-305X. ; 227:8, s. 837-844
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Tidskriftsartikel (refereegranskat)abstract
- The surface failure characteristics of different work roll materials, i.e. High Speed Steel, High Chromium Iron and Indefinite Chill Iron, used in the finishing stands of a hot strip mill have been investigated using stereo microscopy, 3D optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the surface failure mechanisms of work rolls for hot rolling are very complex, involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. Despite the differences in chemical composition and microstructure, the tribological response of the different work roll materials was found to be strongly dependent on second phase constituents such as the size, morphology and distribution of different carbide phases and graphite (in the case of Indefinite Chill Iron) which was found to promote cracking. Cracking and chipping of the work roll surfaces, both having a negative impact on work roll wear, are strongly influenced by the presence of carbides, carbide networks and graphite in the work roll surface. Consequently, the amount of carbide forming elements as well as the manufacturing process must be controlled in order to obtain an optimised microstructure and a predictable wear rate.
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