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  • 101.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S
    Uppsala Universitet.
    Influence of tool steel microstructure on initial material transfer in metal forming: in situ studies in the SEM2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2, p. 1249-1256Article in journal (Refereed)
    Abstract [en]

    Metal forming constitutes a group of industrially important processes to form metallic components to net shape. When forming aluminium and other materials that tend to stick to the tools, problems associated with material transfer, e.g. galling, may occur. In a previous study by the present authors, in situ observations of aluminium transfer during sliding contact in the SEM revealed that the surface topography and chemical composition of the tool steel counter surface have a strong impact on the initial material transfer tendency. Even if carefully polished to a very smooth surface (Ra<50 nm), transfer of aluminium was found to immediately take place on a very fine scale and preferentially to the surface irregularities presented by the slightly protruding M(C,N) particles (height 15 nm) in the tool steel. In contrast, the less protruding M6C carbides, as well as the martensitic steel matrix exhibited very little initial transfer. The mechanism behind the preferential pick-up tendency displayed by the M(C,N) particles was not fully understood and it was not possible to determine if the decisive mechanism operates on the microstructural scale, the nanoroughness scale or the chemical bonding scale. In the present study, these mechanisms have been further investigated and analysed by comparing the very initial stages of material transfer onto different types of tool steels in sliding contact with aluminium in the SEM. The tool steels investigated cover conventional ingot cast and powder metallurgy steel grades, selected to possess a range of different types, amounts and sizes of hard phase particles, including MC, M(C,N), M7C3 and M6C. The transfer mechanisms are investigated using high resolution SEM, and the differences between the different microstructures and carbide types are carefully analysed. The implications for real metal forming are discussed.

  • 102.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S
    Uppsala Universitet.
    Initial deformation and wear of cemented carbides for rock drilling as evaluated by a sliding wear test2015In: Proceedings of International Tribology Conference 2015, 2015Conference paper (Refereed)
  • 103. Heinrichs, J.
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S.
    Initial deformation and wear of cemented carbides in rock drilling as examined by a sliding wear test2017In: International journal of refractory metals & hard materials, ISSN 0263-4368, Vol. 64, p. 7-13Article in journal (Refereed)
    Abstract [en]

    Due to a combination of high hardness and toughness, resulting in excellent wear resistance, cemented carbides are commonly used as the rock crushing component in rock drilling. The present paper presents a unique study where the very initial stages of deformation and wear of cemented carbide in sliding contact with rock are followed in small incremental steps. After each step, a pre-determined area within the wear mark is characterized using high resolution SEM and EDS. This facilitates analysis of the gradual deformation, material transfer, degradation and wear. The deterioration mechanisms found in this sliding test are similar to those observed in actual rock drilling. Cemented carbide grades with different microstructures show significant differences, where a higher amount of Co and a larger WC grain size both are associated to more wear. 

  • 104.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Olsson, Mikael
    Jacobson, S
    Uppsala Universitet.
    Initiation of Galling in Metal Forming: Differences Between Aluminium and Austenitic Stainless Steel Studied In Situ in the SEM2013In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 50, no 3, p. 431-438Article in journal (Refereed)
    Abstract [en]

    High friction and transfer of work material to tool surfaces constitute important industrial problems in forming of many metals and alloys. However, it is very hard to gain a deeper understanding of these phenomena by studying real forming operations. In this paper, we have tried to gain fundamental understanding by avoiding as much as possible of the complexity of real forming. This has been realised by studying the friction and material transfer between well-defined tool material surfaces; uncoated and DLC-coated tool steel, and a needle shaped austenitic stainless steel tip, in situ in the SEM. The tool materials were tested in two conditions; well polished and well polished with local intentional scratches. It was found that work material was immediately transferred to the tool steel surface. When passing an intentional scratch, the local transfer was on a much larger scale, and the friction was higher, but the effect was mostly local. For the polished DLC-coated surface, almost no work material was transferred and the friction was low. An intentional scratch in the polished DLC surface barely influenced the galling behaviour. The present results are discussed in the light of previously published results from an analogous study with aluminium as work material.

  • 105.
    Heinrichs, J.
    et al.
    Uppsala universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala universitet.
    Jacobson, S.
    Uppsala universitet.
    Surface degradation of cemented carbides in scratching contact with granite and diamond: the roles of microstructure and composition2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 342, p. 210-221Article in journal (Refereed)
    Abstract [en]

    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.

  • 106. Heinrichs, J.
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala University.
    Yvell, Karin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S.
    On the deformation mechanisms of cemented carbide in rock drilling: Fundamental studies involving sliding contact against a rock crystal tip2018In: International journal of refractory metals & hard materials, ISSN 0263-4368, Vol. 77, p. 141-151Article in journal (Refereed)
    Abstract [en]

    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.

  • 107.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Yvell, Karin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S
    Uppsala Universitet.
    Soft rock scratches hard cemented carbide2015In: Proceedings of Wear of Materials, 2015Conference paper (Refereed)
  • 108.
    Heinrichs, Jannica
    et al.
    Tribomaterials group, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Gerth, Julia
    Tribomaterials group, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Thersleff, Thomas
    Applied Materials Science, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Larsson, Mats
    Primateria AB, Uppsala, Sweden.
    Wiklund, Urban
    Tribomaterials group, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Influence of sliding speed on modes of material transfer as steel slides against PVD tool coatings2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 58, p. 55-64Article in journal (Refereed)
    Abstract [en]

    An intermittent sliding test was used in order to study the formation and build- up of tribofilms during intermittent sliding of PVD coated HSS against case hardening steel (20NiCrMo2). Two cutting tool coatings were tested, TiN and AlCrN, and the influence of sliding speed was evaluated. With moderate speed,  two tribofilms were formed separately, one consisting of Mn, Si, Al and O on an intermediate layer  of Fe and one consisting of Fe, Mn, Cr and O on an intermediate layer of Cr and Mn. At low sliding speeds an uneven transfer of steel occured while high sliding speeds resulted in thermal softening of the substrate leading to coating failure. AlCrN provided better substrate protection at high speeds than TiN did.

  • 109. Heinrichs, Jannica
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala universitet.
    Almqvist, Bjarne
    Jacobson, Staffan
    Initial surface failure and wear of cemented carbides in sliding contact with different rock types2018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 408-409, p. 43-55Article in journal (Refereed)
    Abstract [en]

    The initial wear, deformation and degradation of cemented carbide in contact with different rock types are studied using a crossed cylinder sliding test. The sliding distance is limited to centimetres at a time, interrupted by successive SEM analysis. This allows for careful studies of the gradually changing microstructure of the cemented carbide during the test. Five different rock types are included; granite, metal sulphide ore, mica schist, quartzite and marble. All rock types are very different in microstructure, composition and properties. The cemented carbide grade used for the evaluation contains 6 wt% Co and fine (~ 1 µm) WC grains, a grade commonly used in rock drilling. The results show that the cemented carbide microstructure becomes altered already during the very first contact with rock. The initial wear rate and wear character is highly influenced by the rock type. The initial wear of the cemented carbide is highest against quartzite and lowest against marble.

  • 110.
    Heinrichs, Jannica
    et al.
    Uppsala University.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, Staffan
    Uppsala University.
    Initial wear of cemented carbides in sliding contact with different rock types2016In: Proceedings of the 17th Nordic Symposium on Tribology - Nordtrib 2016, 2016Conference paper (Refereed)
  • 111. Heinrichs, Jannica
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jacobson, Staffan
    Mechanisms of material transfer studied in situ in the SEM: explanations to the success of DLC coated tools in aluminium forming2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 292, p. 49-60Article in journal (Refereed)
    Abstract [en]

    Metal forming constitutes a group of industrially important processes to form metallic components to net shape. When forming aluminium and other materials that tend to stick to the tools, problems occur. The transferred work material increases the friction, which increases the forming forces. Additionally, the transferred work material becomes hardened and then scratches the softer work material in subsequent forming. This process, known as galling, compromises the surface finish of the next pieces to be formed. This paper employs a newly developed technique to investigate the initial stages of transfer at high resolution in situ in the SEM. We show that the complex microscale processes involved can be distinguished into three classes: primary transfer, secondary transfer and damage activated transfer. The damage activated transfer constitutes a new fundamental tribological phenomenon, involving the activation and healing of a soft metal in sliding contact with a harder surface. Damage activation leads to transfer onto surfaces such as the polished DLC in this investigation, which would otherwise not see any transfer. These processes are important when forming aluminium, but are expected to be of general tribological significance, in sliding involving non-perfect lubricant films, especially for soft metals with protective surface oxides. (C) 2012 Elsevier B.V. All rights reserved.

  • 112. Heinrichs, Jannica
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jacobson, Staffan
    New understanding of the initiation of material transfer and transfer layer build-up in metal forming: in situ studies in the SEM2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 292, p. 61-73Article in journal (Refereed)
    Abstract [en]

    The tribological mechanisms behind the initiation of material transfer and build-up of transfer layers in aluminium forming have been studied in situ in the SEM where a tip of aluminium is put into contact with a tool steel surface under controlled sliding contact conditions. By combining in situ observations with post-test high resolution FEG-SEM studies of the contacting surfaces we have shown that aluminium is immediately transferred onto the fine polished tool steel. It was also confirmed that the initial transfer occurs on a very fine scale and is localised to the surface irregularities presented by the slightly protruding carbonitrides. In contrast, the less protruding M6C carbides, as well as the martensitic steel matrix exhibit very little initial transfer. Intentionally made scratches (roughly 5 mu m wide and 2 mu m deep) across the tool surface immediately result in larger scale transfer, which grows upon further passages of work material causing a high coefficient of friction. The study illuminates the extreme value of combining the in situ technique with high-resolution scanning electron microscopy using low acceleration voltage as a mean to detect the very thin initial transfer layers. With the higher acceleration voltages normally used, the transferred aluminium becomes transparent and can hardly be detected. (C) 2012 Elsevier B.V. All rights reserved.

  • 113. Heinrichs Lindgren, J.
    et al.
    Mikado, H.
    Donzel-Gargand, O.
    Surreddi, Kumar Babu
    Dalarna University, School of Information and Engineering, Materials Technology.
    Wiklund, U.
    Kawamura, S.
    Jacobson, S.
    Exploring the tribochemical wear and material transfer caused by Cu15Zn alloys on shearing tools2024In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 542, article id 205274Article in journal (Refereed)
    Abstract [en]

    Cemented carbide tools are extensively used in the zipper industry, including shearing of a pre-formed Cu15Zn wire into individual zipper elements. Although the work material is significantly softer than the tool, wear is the life limiting factor for the tools and is considered to be of tribochemical nature. So far it has not been explained, however, it is known that the wear rate of uncoated, as well as CrC and CrN coated, cemented carbide increases dramatically when Zn is omitted from the Cu alloy. In this paper, worn tool surfaces, including any transferred material, were studied to investigate the tribochemical wear mechanism in detail. Material transfer occurred onto all tool surfaces. Cu and Zn were separated on the sub-micron scale, and preferential transfer of one of the constituents was observed. This is reflected in the outermost surface of the sheared element, which shows a homogeneous composition elsewhere. Oxidation was observed of all tool surfaces, which indicates elements of oxidative wear. Further, any Zn transferred to the tool surfaces was oxidized. Thus, it is suggested that the presence of Zn reduces the oxygen available and consequently reduces the oxidation rate of the tool surfaces, leading to the protective effect previously observed. © 2024 The Authors

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  • 114.
    Hoier, Philipp
    et al.
    Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Surreddi, Kumar Babu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Klement, Uta
    Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Tool wear by dissolution during machining of alloy 718 and Waspaloy: a comparative study using diffusion couples2020In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 106, no 3-4, p. 1431-1440Article in journal (Refereed)
    Abstract [en]

    The wear of metal cutting tools is known to take place by the combined and simultaneous effects of several wear mechanisms. Knowledge of the relative contribution of the individual wear mechanisms is required to understand and predict the tool wear during cutting different workpiece materials and alloys. It has been shown previously that machining two heat resistant superalloys, alloy 718 and Waspaloy, leads to distinctively different tool wears. Even though the subject has been addressed in various studies, there are still open questions regarding the underlying reasons for the differing tool wear rates. In particular, the relative contributions of diffusion/dissolution when machining the two alloys have not been addressed so far. Therefore, a qualitative comparison of the chemical interaction between the tool material and the two superalloys was made by using diffusion couple tests. The aim was to mimic the high temperatures and intimate contact between workpiece and tool material at the tool rake and flank faces during cutting under controlled and static conditions. The obtained results suggest that it is unlikely that differences in flank wear rate when machining the two superalloys are caused by significantly varying magnitudes of tool atoms dissolving into the respective workpiece. Analysis of the tool/superalloy interfaces in the diffusion couples revealed diffusion-affected zones of similar size for both tested superalloys. Increasing test temperature led to enhanced interdiffusion which suggests an increase in tool wear by diffusion/dissolution for higher cutting temperature. For alloy 718, the higher test temperature also led to depletion of carbon together with formation of tungsten within the tool in close vicinity to the interface with the superalloy.

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  • 115. Hooshyar, H.
    et al.
    Jonsson, T.
    Hall, Josefine
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Svensson, J. -E
    Johansson, L. G.
    Liske, J.
    The effect of H2 and H2O on the oxidation of 304L-stainless steel at 600 °C: general behaviour (part I)2016In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 85, no 3-4, p. 321-342Article in journal (Refereed)
    Abstract [en]

    The effect of p(H2O) and p(H2) on the oxidation of 304L stainless steel at 600 °C has been investigated in the present study. The samples were analysed by means of X-ray diffraction, Auger spectroscopy, and scanning electron microscopy equipped with energy dispersive spectroscopy. The results showed that at fixed p(H2), the corrosion rate increased considerably with increasing p(H2O). At fixed p(H2O), the corrosion rate decreased slightly with increasing p(H2). Duplex oxide scales formed during the exposure in all environments. The outer and inner layer consisted of Fe3O4 and (Fe, Cr)3O4, respectively. The latter was mainly in the form of internal oxidation. The Cr-rich oxide formation was observed at the initial oxidation process before oxide breakdown. The Auger analysis also suggested the presence of Cr-rich oxide layer just after the breakaway oxidation. The results indicated that the rate-determining step in the corrosion attack is surface controlled or diffusion controlled through an oxide layer with fixed thickness over time.

  • 116.
    Huang, Shuo
    et al.
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Vida, Adam
    Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary.;Eotvos Lorand Univ, Dept Mat Phys, Pazmany Peter Setany 1-A, H-1117 Budapest, Hungary..
    Li, Wei
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Molnar, David
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Kwon, Se Kyun
    Pohang Univ Sci & Technol, Grad Inst Ferrous Technol, Pohang 37673, South Korea..
    Holmstrom, Erik
    Sandvik Coromant R&D, S-12680 Stockholm, Sweden..
    Varga, Bela
    Transylvania Univ Brasov, Fac Mat Sci, Bulevardul Eroilor 29, Brasov 500036, Romania..
    Varga, Lajos Karoly
    Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Vitos, Levente
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary.;Uppsala Univ, Div Mat Theory, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Thermal expansion in FeCrCoNiGa high-entropy alloy from theory and experiment2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 24, article id 241902Article in journal (Refereed)
    Abstract [en]

    First-principle alloy theory and key experimental techniques are applied to determine the thermal expansion of FeCrCoNiGa high-entropy alloy. The magnetic transition, observed at 649 K, is accompanied by a significant increase in the thermal expansion coefficient. The phase stability is analyzed as a function of temperature via the calculated free energies accounting for the structural, magnetic, electronic, vibrational and configurational contributions. The single-and polycrystal elastic modulus for the ferro-and paramagnetic states of the face-centered and body-centered cubic phases are presented. By combining the measured and theoretically predicted temperature-dependent lattice parameters, we reveal the structural and magnetic origin of the observed anomalous thermal expansion behavior. Published by AIP Publishing.

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  • 117. Hultquist, G.
    et al.
    Graham, M. J.
    Kodra, O.
    Moisa, S.
    Liu, R.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Smialek, J. L.
    Corrosion of copper in distilled water without O-2 and the detection of produced hydrogen2015In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 95, p. 162-167Article in journal (Refereed)
    Abstract [en]

    This paper reports on hydrogen pressures measured during similar to 19,000 h immersion of copper in oxygen-free liquid distilled water. Copper corrosion products have been examined ex-situ by SEM and characterized by XPS and SIMS. XPS strongly indicates a corrosion product containing both oxygen and hydrogen. SIMS shows that oxygen is mainly present in the outer 0.3 mu m surface region and that hydrogen penetrates to depths well below the corrosion product. Thermal desorption spectroscopy shows that the reaction product formed near room-temperature is less stable than that formed in air at 350 degrees C. 

  • 118. Hörnström, S. -E
    et al.
    Karlsson, E.
    Losch, A.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Bay, N.
    Forming of high-strength steels using a hot-melt dry lubricant2010In: 17th International Colloquium Tribology 2010 - Solving Friction and Wear Problems, 2010, Vol. 2, p. 958-971Conference paper (Refereed)
    Abstract [en]

    The increasing use of high strength steels in a variety of mechanical engineering applications has illuminated problems associated with galling in sheet metal forming operations. Galling is a tribological phenomenon associated with transfer of material from the steel sheet to the tool surface during forming resulting in seizure of the tool/steel sheet contact and extensive scratching of the steel sheet surface. As a result, a number of concepts have been developed in order to reduce the tendency to galling in metal forming, including the development of new dry lubricants, new forming tool steel grades and improved surface engineering treatments such as the deposition of low friction CVD and PVD coatings. In the present study the performance of a hot-melt dry lubricant in the forming of hot and cold rolled and hot-dip galvanized high strength steel has been evaluated and compared with a conventional rust protection oil using five different tests methods, i.e. a strip reduction test, a bending under tension test, a stretch-forming test, a pin-on disc test and a strip drawing test. In these tests, two different cold work tool steels, a conventional steel grade and a nitrogen alloyed PM steel grade were evaluated. The results show that the different tests used give consistent results and valuable information concerning the galling tendency of the steel sheet, tool steel and lubricant combinations investigated and when combined can be used to rank the galling resistance of lubricants and tool steels. The results clearly show that the dry lubricant provides better lubrication and generates less galling than the rust protection oil. Also, the nitrogen alloyed PM steel grade shows a significantly higher galling resistance as compared with the conventional steel grade and can, in combination with a dry lubricant, preferably be used in sheet metal forming operations to further improve the galling resistance.

  • 119. Ingemarsson, L.
    et al.
    Halvarsson, M.
    Engkvist, Josefin
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jonsson, T.
    Hellstrom, K.
    Johansson, L. -G
    Svensson, J. -E
    Oxidation behavior of a Mo (Si, Al)(2)-based composite at 300-1000 degrees C2010In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 18, no 4, p. 633-640Article in journal (Refereed)
    Abstract [en]

    The oxidation behavior of a Mo (Si,Al)(2)-based composite of Mo(Si,Al)(2), Al2O3 and Mo-5(Si,Al)(3) (Kanthal Super ER) in synthetic air was investigated. The samples were oxidized isothermally for up to 72 h at 300-1000 degrees C using a thermobalance. The microstructure was analyzed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Auger Electron Spectroscopy (AES) depth profiling. Broad ion beam milling (BIB) was used to prepare cross-sections. Oxidation behavior depended strongly on the composition of the substrate which consisted of a Mo(Si,Al)(2) matrix and the minority phases Mo-5(Si,Al)(3) and Al2O3. At 300-500 degrees C the mass gains were small with parabolic kinetics, oxidation resulting in a mixture of oxides that reflects the substrate composition. At 600 and 700 degrees C the oxide scale is thin and protective and depleted in molybdenum, a mass loss occurring due to MoO3 vaporization. At 1000 degrees C a protective alpha-alumina scale forms. (C) 2009 Elsevier Ltd. All rights reserved.

  • 120.
    Isgren, Peter
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Dragprovstavens geometripåverkan på mätresultatet2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The thesis is based on a comparative investigation of standard SS 112113 with a geometry described as straight and standard SS-EN 1561:2011 with a geometry described as hourglass shaped. The study will provide deeper understanding of the effect that different tensile test geometries and different test speed has on the tensile strength and the variation. The purpose is to find a suitable geometry and test speed that results in a small dispersion on the measured tensile strength. Another purpose is to perform structural studies to investigate how the microstructure affects the measured result. Seventy tensile tests are included in this study and every bar is casted from the same gray iron melt in identical sand molds. The tensile test bars is lathed according respective standard and tensile tested in a Zwick tensile test machine. A light microscopy, LOM has been used for checking defects in the fracture surface, check the roughness of the surface and for graphite classification. A scanning electron microscope, SEM has been used to check rust on the tensile test piece. Hardness testing by Brinell has been performed since there is a connection between tensile strength and hardness. The tensile strength and the dispersion are lower for SS 112113. The fracture occurs at different positions for standard SS 112113. Different tensile test speed does not result in a significant difference in tensile strength or dispersion. For standard SS-EN 1561:2011 the fracture occurs where the cross-sectional area is minimum. Microstructure with regard to graphite type and graphite length does not explain the difference in tensile strength or deviation.

  • 121.
    Ismail, Kasimagwa
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Brabie, Voicu
    The use of thermodynamic computations to predict the phase transformation in MgO-C refractories during steel refining2008In: Refractories Manual, p. 42-47Article in journal (Refereed)
  • 122.
    Istiqamah, Istiqamah
    et al.
    Dalarna University, School of Information and Engineering.
    Shahraki, Sina Soleimani
    Dalarna University, School of Information and Engineering.
    Comparative Life CycleAssessment of Two Single Family Dwellings2022Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study compared the Global Warming Potential (GWP) impact of two single-family dwellings situated in Halmstad and Norrköping. The aim of this thesis work is to investigate how building materials types, material quantities, and geographical boundaries affect the Life Cycle Assessment (LCA) results. This study focuses on climate declaration (A1-A5) LCA stages and was conducted in collaboration with Fiskarhedenvillan.

    The study uses a comparative LCA of various building components and materials. One Click LCA student license was used to calculate the CO2e emissions from the GWP impact category.

    The study found that the building in Halmstad generated 6,3% lower CO2e emissions compared to the building in Norrköping. The reason mainly was affected by the use of roofing materials. The building in Halmstad used reinforced bitumen while the building in Norrköping used concrete tile roofing. The study investigates that reinforced bitumen generates lower emissions in A1-A4 stages compared to concrete.

    The geographical boundaries affect the A4 stage. The building in Halmstad generated higher CO2e emissions compared to the building in Norrköping as it has long distances to the building materials suppliers. The research verifies that the A1-A3 stages considerably generate most of the emissions (70-80%) compared to A4 and A5. The A5 stage results remain the same per meter square of both dwellings considering the use of generic data from One Click LCA.

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  • 123.
    Jacobson, S
    et al.
    Uppsala Universitet.
    Beste, U
    Uppsala Universitet.
    Heinrichs, J
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Wiklund, U
    Uppsala Universitet.
    On the nature of cemented carbide wear in rock drilling2014In: Hard Rock Tribology Course and Seminar, Tampere, Finland, November 4-5, 2014, 2014Conference paper (Other academic)
  • 124. Jansson, S.
    et al.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jonsson, P.
    Magnesia-carbon refractory dissolution in Al killed low carbon steel2006In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 33, no 5, p. 389-397Article in journal (Refereed)
    Abstract [en]

    The effects of rotation speed, steel temperature and steel composition on the rate of dissolution of MgO-C refractory into Al deoxidised molten steel were investigated using the rotating cylinder method. Cylinders or rods of MgO-C refractory material were immersed in an Al deoxidised molten steel. Experiments were performed for steel temperatures between 1873 and 1973 K and rotation speeds between 100 and 800 rev min(-1) as well as for different immersion times. For each case, the dissolution rate of MgO-C material was determined from measurement of the decrease in the rod radius. The experimental results showed that the dissolution rate of the MgO-C refractory material increased with an increase in steel temperature and rotation speed. The findings strongly suggest the diffusion of magnesium through the slag layer formed around the refractory rods to be a rate determining step. This thin oxide layer at the steel/refractory interface was found to be owing to reaction between magnesium vapour and CO generated by the reaction between MgO and C in the refractory. Oxide inclusions were also found in the steel melt and they were shown to mainly consist of MgO and Al2O3 or a mixture of the two.

  • 125. Jansson, Sune
    et al.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jonsson, P.
    Corrosion mechanism of commercial doloma refractories in contact with CaO-Al2O3-SiO2-MgO stag2008In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 35, no 2, p. 99-107Article in journal (Refereed)
    Abstract [en]

    The dissolution of three doloma based refractories in liquid CaO-Al2O3-SiO2-MgO slag was studied. Cylindrical refractory specimens of doloma, carbon bonded doloma, and magnesia doloma were rotated in a stationary crucible of molten slag under forced convection conditions. Slag composition, temperature, rod rotation speed and rod immersion time were varied. The refractory dissolution rate was determined from the change in diameter of the cylindrical specimens. The corrosion rate was found to increase with temperature and rod rotation speed and decrease when the slag was nearly saturated with MgO. The findings of the study substantiate the assumption that the diffusion of magnesium oxide through the slag boundary layer controls the corrosion process. The results indicated the overall corrosion process to be the dissolution of refractory material into the slag, followed by slag penetration of the pores and grain boundaries and finally, dispersion of the grains into the slag.

  • 126. Jansson, Sune
    et al.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Josson, Par
    Corrosion mechanism of commercial MgO-C refractories in contact with different gas atmospheres2008In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 48, no 6, p. 760-767Article in journal (Refereed)
    Abstract [en]

    Corrosion of MgO-C refractories in different gas atmospheres consisting of air, Ar, CO or Ar/CO was studied in laboratory experiments. In total, 103 experiments were carried out in the temperature range 1 173 to 1 773 K and for holding times between 2 to 120 min. The reaction rate of the MgO-C material was determined from measurements of the weight loss of the samples. The results showed that the refractory weight loss increased with an increased temperature or an increased holding time. The thermodynamic conditions and the experimental results showed that magnesium gas and carbon monoxide gas should form during ladle refining of steel when the refractory material consists of MgO-C. It was suggested that the reaction rate is directly dependent on the oxygen potential in the ambient atmosphere.

  • 127. Jansson, Sune
    et al.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jönsson, Pär
    Corrosion mechanism and kinetic behaviour of MgO-C refractory material in contact with CaO-Al2O3-SiO2-MgO slag2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 5, p. 283-292Article in journal (Refereed)
    Abstract [en]

    The rate of dissolution of solid MgO-C into liquid CaO-Al2O3-SiO2-MgO slag at different temperatures was studied under conditions of forced convection by rotating cylindrical refractory specimens in a stationary crucible containing molten slag. The corrosion rate was calculated from the change in diameter of the cylindrical refractory specimens. The specimens were rotated for 15-120 min at a speed of 100-400 rpm in the molten slag. The rate of corrosion was found to increase with an increase in temperature and rod rotation speed, and to decrease when the slag was nearly saturated with MgO. The experimental results support the assumption that the diffusion of magnesium oxide through the slag-phase boundary layer controls the corrosion process. The corrosion mechanism seems to be the dissolution of refractory material into the slag followed by penetration of pores and grain boundaries and dispersion of the grains into the slag.

  • 128. Jayalakshmi, Subramanian
    et al.
    Arvind Singh, Ramachandra
    Shabadi, Rajashekhara
    Jayamani, Jayaraj
    Seshan, Sambasivam
    Gupta, Manoj
    An Overview of Viable Unconventional Processing Methods for Advanced Materials2018In: Manufacturing Techniques for Materials / [ed] T.S. Srivatsan, T.S. Sudarshan, K. Manigandan, Boca Raton: CRC Press, 2018, , p. 814Chapter in book (Refereed)
  • 129.
    Jayamani, Jayaraj
    et al.
    Dalarna University, School of Information and Engineering, Materials Technology.
    Elo, Robin
    Uppsala University.
    Surreddi, Kumar Babu
    Dalarna University, School of Information and Engineering, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Information and Engineering, Materials Technology.
    Electrochemical and passivation behavior of a corrosion-resistant WC-Ni(W) cemented carbide in synthetic mine water2023In: International journal of refractory metals & hard materials, ISSN 0263-4368, Vol. 114, article id 106227Article in journal (Refereed)
    Abstract [en]

    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 μm). 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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  • 130. Jayamani, Jayaraj
    et al.
    Fleury, E.
    Park, B. J.
    Kim, D. H.
    Kim, W. T.
    Synthesis and characterization of nanometer-sized Ti-based amorphous powders2007In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 22, no 6Article in journal (Refereed)
    Abstract [en]

    We present a simple method for preparing nanometer-sized, Ti-based amorphous powders from the Y28Ti28Al24Co20and Y36Ti20Al24Co20two-phase amorphous alloys. The initial microstructure of these rapidly quenched alloys is composed of Ti-based, amorphous, spherical, nanometer-sized particles embedded in a Y-based amorphous matrix, with particle size dependent on the alloy composition. The Ti-based powders were extracted from the two-phase amorphous alloys through selective dissolution of the Y-rich matrix in a 0.1 M HNO3solution. The powders of size ranging between 20 and 200 nm have smooth and spherical morphology, and exhibit different magnetic behavior than the bulk alloy of identical composition.

  • 131. Jayamani, Jayaraj
    et al.
    Fleury, Eric
    Kim, Ki-Bae
    Lee, Jae-Chul
    Globulization mechanism of the primary Al of Al−15Cu alloy during slurry preparation for rheoforming2005In: Metals and Materials International, ISSN 1598-9623, E-ISSN 2005-4149, Vol. 11, no 3Article in journal (Refereed)
    Abstract [en]

    Semisolid slurries of Al-15Cu alloy were produced for rheoforming by a low temperature pouring technique. To investigate the morphological change of the slurry in terms of the particle mean diameter and the roundness factor, samples were extracted during the continuous cooling and the isothermal holding stage of the slurry by a simple technique of interrupt quenching. Results demonstrated that the fine-grained equiaxed dendritic structure, which formed during low temperature pouring, is changed to a globular structure when held at a semisolid temperature for sufficiently long holding time. With regard to the globulization mechanism of the primary α-phase, local melting is considered to take place at the neck of equiaxed dendrites, leading to the separation of small new particles during continuous cooling. These newly formed particles eventually grow during isothermal holding in the semisolid temperature by obeying theD3=Kt kinetic law, which suggests coarsening by Ostwald ripening.

  • 132. Jayamani, Jayaraj
    et al.
    Gebert, A.
    Schultz, L.
    Passivation behaviour of structurally relaxed Zr48Cu36Ag8Al8 metallic glass2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 479, no 1, p. 257-261Article in journal (Refereed)
    Abstract [en]

    The electrochemical corrosion behaviour of as-prepared and structurally relaxed Zr48Cu36Ag8Al8 glassy alloy samples was investigated in 1M H2SO4. Results show that the active–passive transition behaviour of Zr48Cu36Ag8Al8 glassy alloy depends on the amount of free volume (FV) present in the metallic glassy alloy. Poor passivation due to active dissolution of Cu was displayed by the Zr48Cu36Ag8Al8 glassy alloy when it was in a high energy metastable state with relative high amount of FV. It is shown that by reducing the amount of FV in the glass, the passivation behaviour is significantly improved.

  • 133.
    Jayamani, Jayaraj
    et al.
    Korea Institute of Science and Technology, South Korea.
    Han, Jae Ho
    Park, Sang Whan
    Kim, Ki Bae
    Fleury, Eric
    Potential of Cr2AlC Ternary Carbide as Material for Bipolar Plate in PEMFC2007In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 124-126, p. 927-930Article in journal (Refereed)
    Abstract [en]

    In this paper, we present results of an investigation on the physical, mechanical, chemical properties and processing ability of the Cr2AlC ternary carbide bulk material synthesized by hot pressing technique. The combination of excellent properties indicated that Cr2AlC ternary carbide alloy could be potential candidate materials as bipolar plates in polymer membrane fuel cell (PEMFC).

  • 134. Jayamani, Jayaraj
    et al.
    Kim, K. B.
    Ahn, H. S.
    Fleury, E.
    Corrosion mechanism of N-containing Fe–Cr–Mo–Y–C–B bulk amorphous alloys in highly concentrated HCl solution2007In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 449-451, p. 517-520Article in journal (Refereed)
    Abstract [en]

    The Fe49Cr15.3Mo15Y2C15B3.4N0.3 (numbers indicate at.%) amorphous alloy in concentrated HCl solution was found to have a corrosion resistance of at least one order of magnitude higher than the N-free Fe-base amorphous alloy. X-ray photoelectron spectroscopy analyses were performed to understand the corrosion mechanism. It was found that the enrichment of Cr oxide and the presence of MoN nitrides on the surface in the passive layer were at the origin of the high corrosion resistance of the N-containing Fe-base amorphous alloy.

  • 135. Jayamani, Jayaraj
    et al.
    Kim, Y. C.
    Kim, K. B.
    Seok, H. K.
    Fleury, E.
    Corrosion behaviors of Fe45−xCr18Mo14C15B6Y2Mx (M=Al, Co, Ni, N and x=0, 2) bulk metallic glasses under conditions simulating fuel cell environment2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 434-435, p. 237-239Article in journal (Refereed)
    Abstract [en]

    The corrosion properties of the Fe45−xCr18Mo14C15B6Y2Mx (with M=Al, Co, Ni, N and x=0, 2) bulk metallic glasses have been investigated in a 1M H2SO4+2ppm F− solution at 80°C with H2 and air bubbling, which simulate environments of the polymer electrolyte membrane fuel cell. The partial replacement of 2at.% Fe led to significant modification of the corrosion behavior and resulted in corrosion resistances superior to that of stainless steel.

  • 136. Jayamani, Jayaraj
    et al.
    Kim, Y. C.
    Kim, K. B.
    Seok, H. K.
    Fleury, E.
    Corrosion studies on Fe-based amorphous alloys in simulated PEM fuel cell environment2005In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 6, no 3-4, p. 282-289Article in journal (Refereed)
  • 137. Jayamani, Jayaraj
    et al.
    Kim, Y. C.
    Seok, H. K.
    Kim, K. B.
    Fleury, E.
    Development of metallic glasses for bipolar plate application2007In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 449-451, p. 30-33Article in journal (Refereed)
    Abstract [en]

    Fe- and Ni-base amorphous alloys were developed and characterized as alternative bipolar plate materials for polymer electrolyte membrane fuel cell (PEMFC). Lower interfacial contact resistances were obtained for the Fe-base in comparison with Ni-base alloys and particularly the N-containing Fe-base amorphous composition exhibited values almost comparable to that of stainless steel upon high compaction load. Under conditions simulating the anodic and cathodic PEMFC environments, both the Fe- and Ni-base amorphous alloys displayed higher corrosion resistance than stainless steel.

  • 138. Jayamani, Jayaraj
    et al.
    Krishnaveni, P.
    Krishna, D. Nanda Gopala
    Mallika, C.
    Mudali, U. Kamachi
    Corrosion investigations on zircaloy-4 and titanium dissolver materials for MOX fuel dissolution in concentrated nitric acid containing fluoride ions2016In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 473, p. 157-166Article in journal (Refereed)
    Abstract [en]

    Aqueous reprocessing of plutonium-rich mixed oxide fuels require fluoride as a dissolution catalyst in boiling nitric acid for an effective dissolution of the spent fuel. High corrosion rates were obtained for the candidate dissolver materials zircaloy-4 (Zr-4) and commercial pure titanium (CP-Ti grade 2) in boiling 11.5 M HNO3 + 0.05 M NaF. Complexing the fluoride ions either with Al(NO3)3 or ZrO(NO3)2 aided in decreasing the corrosion rates of Zr-4 and CP-Ti. From the obtained corrosion rates it is concluded that CP-Ti is a better dissolver material than Zr-4 for extended service life in boiling 11.5 M HNO3+0.05 M NaF, when complexed with 0.15 M ZrO(NO3)2. XPS analysis confirmed the presence of TiO2 and absence of fluoride on the surface of CP-Ti samples, indicating that effective complexation had occurred in solution leading to passivation of the metal and imparting high corrosion resistance.

  • 139. Jayamani, Jayaraj
    et al.
    Mendis, C. L.
    Ohkubo, T.
    Oh-ishi, K.
    Hono, K.
    Enhanced precipitation hardening of Mg–Ca alloy by Al addition2010In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 63, no 8, p. 831-834Article in journal (Refereed)
    Abstract [en]

    We report the enhanced precipitation-hardening response of Mg–0.5Ca (wt.%) alloy by microalloying with Al. The peak hardness of 50 HV for the binary alloy was enhanced to 72 HV in a ternary Mg–0.5Ca–0.3Al alloy. Transmission electron microscopy and 3D atom probe analyses confirmed that the improvement in the peak hardness is associated with the dense precipitation of ordered monolayer Guinier–Preston zones and the subsequent formation of Al2Ca causes the over-aging.

  • 140.
    Jayamani, Jayaraj
    et al.
    National Institute for Materials Science, Tsukuba, Japan.
    Mendis, C. L.
    Ohkubo, T.
    Oh-ishi, K.
    Hono, K.
    Precipitation hardenable Mg-Ca-Al alloys2011In: Magnesium Technology 2011 / [ed] Sillekens, Wim H.; Agnew, Sean R.; Neelameggham, Neale R.; Mathaudhu, Suveen N, Cham: Springer International Publishing , 2011, p. 245-248Chapter in book (Refereed)
    Abstract [en]

    The age-hardening responses and the corresponding microstructures of Mg-0.5Ca-xAl (x = 0, 0.1, 0.3, 0.5, 1 wt. %) alloys were investigated by hardness tests and transmission electron microscopy. For the optimum Al addition of 0.3 wt. % an enhanced age-hardening response with the highest peak hardness of HV=72 was achieved. TEM analyses confirmed that the improvement in the peak hardness is associated with the dense precipitation of ordered monolayer G.P. zones. Whereas, lower content of Al resulted in the formation of G.P. zones and Mg2Ca and the excess addition of Al causes the formation of the G.P. zones and the grain boundary Al2Ca phase.

  • 141. Jayamani, Jayaraj
    et al.
    Mudali, U. Kamachi
    Electrochemical Activity at the Interface of Dissimilar Explosive Joint of Stainless Steel with Zircaloy by Scanning Electrochemical Microscopy2012In: Journal of Advanced Microscopy Research, ISSN 2156-7573, E-ISSN 2156-7581, Vol. 7, no 3, p. 214-217Article in journal (Refereed)
    Abstract [en]

    Electrochemical activity at the interface of dissimilar explosive joint of stainless steel with Zircaloy has been studied in 11.5 M nitric acid using scanning electrochemical microscopy. The reduction of nitric acid and oxidation of nitrous acid in the tip-substrate gap is proposed as a mechanism for the electron transfer reaction. Due to this reaction increase in tip current was observed, indicating that the positive feedback mode of SECM is under operation. The difference in tip current was correlated with the microstructure and the electrochemical activity of the dissimilar weld interface.

  • 142. Jayamani, Jayaraj
    et al.
    Nanda Gopala Krishna, D.
    Mallika, C.
    Kamachi Mudali, U.
    Electrochemical Studies and XPS Analysis of the Surface of Zirconium-702 in Concentrated Nitric Acid With and Without Fluoride Ions2018In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 71, no 3, p. 521-531Article in journal (Refereed)
    Abstract [en]

    Zirconium exhibited pseudo-passive behavior in fluorinated nitric acid (11.5 M HNO3 + 0.05 M NaF) as the current density measured from the electrochemical studies was several orders higher than the value in fluoride free nitric acid. Impedance studies on zirconium sample exposed in 11.5 M HNO3 for 240 h confirmed the formation of the passive film with high polarization resistance value and the calculated thickness of the film based on the capacitance value was about ~4.5 nm. On the other hand, in fluorinated nitric acid, the charge transfer resistance value associated with the zirconium dissolution process was dominant when compared to that of the film formation. Results of X-ray photoelectron spectroscopic investigations upheld the presence of ZrOF2 and ZrF4 and indicated that the protective oxide layer growth was restricted by the presence of fluoride ions.

  • 143. Jayamani, Jayaraj
    et al.
    Nanda Gopala Krishna, D.
    Mallika, C.
    Kamachi Mudali, U.
    Passive film properties and corrosion behavior of Ni–Nb and Ni–Nb–Ta amorphous ribbons in nitric acid and fluorinated nitric acid environments2015In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 151, p. 318-329Article in journal (Refereed)
    Abstract [en]

    Potentiodynamic polarization and electrochemical impedance studies revealed the passivation ability and corrosion resistance of Ni60Nb40 and Ni60Nb30Ta10 amorphous ribbons in 11.5 M HNO3 and 11.5 M HNO3 + 0.05 M NaF media at room temperature. Mott–Schottky analysis indicated the formation of n-type semiconducting passive film on these amorphous ribbon samples. Electrochemical parameters such as corrosion current density, passivation current density and donor density confirmed the passive film property of Ni60Nb30Ta10 amorphous ribbon to be superior to that of Ni60Nb40 amorphous ribbon. Weight loss was insignificant in Ni60Nb30Ta10 ribbon exposed to boiling 11.5 M HNO3 for 240 h. XPS analysis revealed that the origin of passivity of Ni60Nb40 and Ni60Nb30Ta10 amorphous ribbons in boiling 11.5 M HNO3 was due to the formation of a relatively thick passive film of ≈3 nm enriched with Nb2O5 and a thin passive film of ≈1.5 nm enriched with both Nb2O5 and Ta2O5 on the respective ribbon's surface. In boiling fluorinated nitric acid, Ni60Nb40 ribbon underwent severe dissolution owing to the instability of Nb-oxide passive film and the oxide/metal interface.

  • 144.
    Jayamani, Jayaraj
    et al.
    Dalarna University, School of Information and Engineering, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Information and Engineering, Materials Technology.
    Effect of tribo-layer on the corrosion behavior of WC-Co and WC-Ni cemented carbides in synthetic mine water2021In: International journal of refractory metals & hard materials, ISSN 0263-4368, Vol. 100, article id 105621Article in journal (Refereed)
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  • 145. Jayamani, Jayaraj
    et al.
    Park, B. J.
    Kim, D. H.
    Kim, W. T.
    Fleury, E.
    Nanometer-sized porous Ti-based metallic glass2006In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 55, no 11, p. 1063-1066Article in journal (Refereed)
    Abstract [en]

    A porous Ti-based metallic glass has been fabricated by applying the principle of dealloying to the Y20Ti36Al24Co20 two-phase amorphous alloy. The initial microstructure of the two-phase glassy alloy consisted of Ti43.3Y3.7Al15.3Co37.7 and Y38.8Ti12.8Al37.1Co11.3 amorphous phases forming an interconnected structure. To fabricate the porous structure, the Y-rich phase has been selectively dissolved from the alloy using both chemical and electrochemical treatments in 0.1M HNO3 solution. The glassy nature of the porous Ti-based alloy was confirmed by transmission electron microscopy analyses.

  • 146. Jayamani, Jayaraj
    et al.
    Park, J. M.
    Gostin, P. F.
    Fleury, E.
    Gebert, A.
    Schultz, L.
    Nano-porous surface states of Ti–Y–Al–Co phase separated metallic glass2009In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 17, no 12, p. 1120-1123Article in journal (Refereed)
    Abstract [en]

    A novel nano-porous state was fabricated at the surface of the Ti-based metallic glass by selective etching technique. By transforming the surface of the Ti45Y11Al24Co20 phase separated alloy from smooth towards rough with nano-pores in an oxidised state, the passivation behaviour of the glassy alloy in simulated body fluid condition was remarkably improved leading to corrosion resistance significantly higher than that of the Ti–6Al–4V alloy, one of the favourite candidate materials for implant applications.

  • 147. Jayamani, Jayaraj
    et al.
    Ranjith, P. M.
    Ningshen, S.
    Ramanathan, S.
    Studies on Corrosion of Titanium and Air-Oxidized Titanium in Fluorinated Nitric Acid2019In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 72, no 7, p. 1917-1926Article in journal (Refereed)
    Abstract [en]

    Titanium (Ti) is a lustrous transition metal which possesses excellent corrosion resistance in several aggressive environments but is attacked by acidic fluoride media. In this work, the addition of fluoride ion to nitric acid on the corrosion behavior of Ti and air-oxidized Ti was studied. Air oxidation of Ti at 800 °C for 5 h resulted in the formation of an intact rutile TiO2 layer with a thickness of about 35 μm. The corrosion resistance was investigated from the polarization resistance ($$R_{\text{P}}$$RP) values which were obtained from linear polarization and electrochemical impedance spectroscopy (EIS) measurements. A decrease in the $$R_{\text{P}}$$RPvalue of Ti with the addition of fluoride ion in nitric acid was observed, and this indicated the formation of an unstable layer, which resulted in accelerated dissolution. The several order increase in the $$R_{\text{P}}$$RPvalue of air-oxidized Ti in nitric acid containing fluoride ions pointed the improved resistance to corrosion. The diffusivity of species through the air-oxidized TiO2 layer was estimated from the electrochemical equivalent circuit (EEC) analysis of EIS data. Even though the diffusivity increased by several orders with the addition of fluoride ions, air-oxidized Ti provided better protection against nitric acid containing fluoride ions than Ti. The corrosion rates of Ti and air-oxidized Ti in boiling nitric acid containing fluoride ions were also estimated from weight loss experiments. Even in boiling fluorinated nitric acid, air-oxidized Ti provided better corrosion protection, with corrosion rates of about 1000 times less than that of Ti.

  • 148. Jayamani, Jayaraj
    et al.
    Ravi, K. R.
    Mallika, C.
    Kamachi Mudali, U.
    Microstructure and Corrosion Behavior of Hf-40 Wt Pct Ti Alloy in Nitric Acid Medium for Reprocessing Applications2016In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 47, no 9, p. 4393-4403Article in journal (Refereed)
    Abstract [en]

    The Hf-40 wt pct Ti (Hf-Ti) alloy was developed for neutron poison application in the spent nuclear fuel reprocessing plant. The furnace-cooled Hf-Ti sample exhibited the microstructure comprising equiaxed-α, lamellar-α, and feathery-α. The water-quenched Hf-Ti sample confirmed the presence of lath and internally twinned martensite. In comparison to the furnace-cooled sample, low corrosion current density and passivation current density values obtained for the water-quenched Hf-Ti in 6 M HNO3 at 298 K (25 °C) indicated better passivation ability. The martensitic structure exhibited high hardness (660 HV) and negligible corrosion rate in 6 M nitric acid at 298 K (25 °C). X-ray photoelectron spectroscopic (XPS) analysis confirmed that passivation behavior of this alloy was due to the protective passive film composed of TiO2 and HfO2.

  • 149. Jayamani, Jayaraj
    et al.
    Ravi Shankar, A.
    Kamachi Mudali, U.
    Electrochemical and passive characterization of a beta type Ti45Zr38Al17 cast rod in nitric acid medium2012In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 85, p. 210-219Article in journal (Refereed)
    Abstract [en]

    Electrochemical behavior of the recently developed beta-type Ti–38at% Zr–17at% Al (TZA) alloy has been studied in nitric acid medium for applications in nuclear reprocessing plant. Potentiodynamic polarization and electrochemical impedance studies revealed that the passive film formed on the TZA alloy was highly protective in nature. Mott–Schottky analysis of the passive film formed on TZA alloy showed n-type semiconducting properties. The electrochemical data confirmed the superior corrosion resistance of TZA alloy as the passive film formed exhibited better properties than that of the commercial pure Ti. XPS analyses confirmed that the stable passivity of TZA alloy in nitric acid was due to the formation of thick and protective passive layer, predominantly of ZrO2 with TiO2.

  • 150.
    Jayamani, Jayaraj
    et al.
    Korea Institute of Science and Technology, Seoul, Korea.
    Seok, H.K.
    Korea Institute of Science and Technology, Seoul, Korea.
    Byun, K.H.
    Korea Institute of Science and Technology, Seoul, Korea.
    Fleury, E.
    Korea Institute of Science and Technology, Seoul, Korea.
    Hong, K.T.
    Korea Institute of Science and Technology, Seoul, Korea.
    Advanced Metallic coating for the improvement of corrosion and erosion resistance of iron based materials used in buildings and special works2005In: Corrosion Science and Technology, ISSN 2288-6524, Vol. 4, no 2, p. 64-68Article in journal (Refereed)
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