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  • 1.
    Bigdeli, S.
    et al.
    Chalmers .
    Kjellqvist, L.
    Thermo-Calc Software AB, Ra ̊sundava ̈gen 18, 169 67 Solna, Sweden.
    Naraghi, R.
    Thermo-Calc Software AB, Ra ̊sundava ̈gen 18, 169 67 Solna, Sweden.
    Höglund, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures. Thermo-Calc Software AB, Råsundavägen 18, 169 67 Solna, Sweden.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures. Thermo-Calc Software AB, Råsundavägen 18, 169 67 Solna, Sweden.
    Jonsson, T.
    Chalmers.
    Strategies for High-Temperature Corrosion Simulations of Fe-Based Alloys Using the Calphad Approach: Part I2021In: Journal of Phase Equilibria and Diffusion, ISSN 1547-7037, Vol. 42, no 3, p. 403-418Article in journal (Refereed)
    Abstract [en]

    The environmental degradation of materials at high temperatures limits the useful life of different industrial components and hinders the development of more economical and environmentally friendly processes for the energy production. Despite the importance of this phenomena, a model to predict lifetime of materials that degrade due to high-temperature corrosion has up till now been lacking due to limitations of the computational possibilities and the complex nature of oxidation. In the present work we develop some strategies to model high-temperature corrosion in Fe-based alloys using the Calphad (Calculation of Phase Diagrams) approach. It is proposed that kinetic-based simulations for oxidation of Al and Cr can accurately represent the lifetime of the protective layers in FeCrAl and FeCr alloys at different temperatures in air. The oxide systems are in addition investigated by equilibrium calculations. The corrosion mechanisms of FeCr and FeCrAl alloys are discussed based on theoretical and experimental knowledge.

  • 2.
    Bjerke, Axel
    et al.
    Lund Univ, Div Prod & Mat Engn, Ole Romers Vag 1, Lund, Sweden..
    Hrechuk, Andrii
    Lund Univ, Div Prod & Mat Engn, Ole Romers Vag 1, Lund, Sweden..
    Lenrick, Filip
    Lund Univ, Div Prod & Mat Engn, Ole Romers Vag 1, Lund, Sweden..
    Markstrom, Andreas
    Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Norgren, Susanne
    Sandvik R&D, Lerkrogsv 13, S-12680 Stockholm, Sweden..
    M'Saoubi, Rachid
    Seco Tools AB, R&D Mat & Technol Dev, S-73782 Fagersta, Sweden..
    Bjork, Thomas
    Ovako Grp, Olof Hjorts Vag 2, S-81335 Hofors, Sweden..
    Bushlya, Volodymyr
    Lund Univ, Div Prod & Mat Engn, Ole Romers Vag 1, Lund, Sweden..
    Thermodynamic modeling framework for prediction of tool wear and tool protection phenomena in machining2021In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 484-485, article id 203991Article in journal (Refereed)
    Abstract [en]

    Chemical, oxidational and diffusional interactions between the tool, chip and cutting environment are known tool wear mechanisms in machining. However, the interaction between tool, coating, workpiece, coolant and atmospheric oxygen can, under favorable conditions, lead to formation of reaction products that retard tool wear. A method with the ability to predict theses interactions, would therefore enable a better control over tool life in machining. An attempt to create such a modelling framework is developed in this study. This method can predict the phase composition and the driving force for degradation and the formation of protective interaction products in the cutting zone. This modeling approach is applicable across cutting processes in which chemical, diffusional and oxidational wear are dominant or present. This framework has been applied to investigate the interactions occurring in the cutting zone during turning of a medium alloyed low-carbon steel (Hybrid Steel (R) 55). A range of degradation events are predicted, as well as the formation of a protective corundum (Al,Fe,Cr)(2)O-3 or spinel (Al, Fe,Cr)(3)O-4 film due to an interaction between the Al-alloyed steel and the environment. Validation of the modeling was performed by studying tool wear and reaction products formed when machining with ceramics, PcBN and coated carbide tooling. Inserts are studied by the use of scanning and transmission electron microscopy, after cutting tests were performed. Additional tests were performed in different environments (dry, argon and coolant). The results confirmed the model predictions of oxidation and diffusion wear as well as the formation of an (Al,Fe,Cr)(3)O-4 tool protection layer. Thus, the proposed thermodynamic framework seem promising to serve as a predictive instrument for the correct pairing of existing tool and workpiece combinations and cutting parameters, or for tailoring respective material compositions for intentional formation of a tool protection layer. As well as guidance on how to apply present and future kinetic models when concurrent interaction mechanisms are present. Which lead to a reduction and minimization of costly experimental machining tests.

  • 3.
    Bjerke, Axel
    et al.
    Lund Univ, Div Prod & Mat Engn, Ole Romers Vag 1, Lund, Sweden..
    Hrechuk, Andrii
    Lund Univ, Div Prod & Mat Engn, Ole Romers Vag 1, Lund, Sweden..
    Lenrick, Filip
    Lund Univ, Div Prod & Mat Engn, Ole Romers Vag 1, Lund, Sweden..
    M'Saoubi, Rachid
    Seco Tools AB, R&D Mat & Technol Dev, S-73782 Fagersta, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Markström, Andreas
    Thermo Calc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Björk, Thomas
    Ovako Grp, Olof Hjorts Vag 2, S-81335 Hofors, Sweden..
    Norgren, Susanne
    Sandvik Coromant R&D, Lerkrogsv 13, S-12680 Stockholm, Sweden..
    Ståhl, Jan-Eric
    Lund Univ, Div Prod & Mat Engn, Ole Romers Vag 1, Lund, Sweden..
    Bushlya, Volodymyr
    Lund Univ, Div Prod & Mat Engn, Ole Romers Vag 1, Lund, Sweden..
    Onset of the degradation of CVD alpha-Al2O3 coating during turning of Ca-treated steels2021In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 477, article id 203785Article in journal (Refereed)
    Abstract [en]

    The ability to control the shape, distribution and composition of non-metallic inclusions has had an important impact on many aspects of steel making. One such impact is on the machinability. Ca-treatments have shown to be able to reduce the abrasiveness of oxide inclusions, improve chip-breaking and lead to formation of deposits that reduce tool wear. However, machining Ca-treated steels with Al2O3 coated cemented carbide tools has not been as advantageous as expected. This study investigates the mechanisms behind the anomalous wear of Al2O3 coatings when turning soft Ca-treated steels. Longitudinal turning tests at a range of speeds (vc = 100-600 m/min) show rapid localized degradation of the Al2O3 coating limited to the sliding zone. Detailed analysis of the degradation mechanisms was performed using scanning and transmission electron microscopy. The results demonstrate a presence of chemical interactions between the alumina coating and non-metallic inclusions. The interaction resulted in the formation of mainly calcium aluminates and partly alumina-magnesia spinel. In-operando infrared thermography measurements indicate cutting temperatures of 850-1000 degrees C. Thermodynamic calculations give that CaO and MgO readily reacts with Al2O3, while the reaction with CaS requires presence of additional oxygen at these cutting conditions. Additional turning experiments investigate the influence of oxygen by controlling the cutting environment by adding oxygen (compressed air) or removing oxygen (supply argon). These additional tests show that the presence of additional oxygen has a limited impact on the possible Ca-Al2O3 interaction. This demonstrat a potential for further machinability improvements by controlling the chemical interaction between Ca and Mg based non-metallic inclusions and alumina coatings.

  • 4.
    Bjerke, Axel
    et al.
    Division of Production and Materials Engineering, Lund University, Ole Römers väg 1, Lund, Sweden.
    Lenrick, Filip
    Division of Production and Materials Engineering, Lund University, Ole Römers väg 1, Lund, Sweden.
    Norgren, Susanne
    Division of Production and Materials Engineering, Lund University, Ole Römers väg 1, Lund, Sweden; Sandvik Coromant R&D, Lerkrogsv. 13, Stockholm, 126 80, Sweden.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Markstrom, Andreas
    Thermo-Calc Software AB, Råsundavägen 18, Solna, SE-169 67, Sweden.
    M'Saoubi, Rachid
    Division of Production and Materials Engineering, Lund University, Ole Römers väg 1, Lund, Sweden; R&D Materials and Technology Development, Seco Tools AB, Fagersta, 737 82, Sweden.
    Petrusha, Igor
    Institute for Superhard Materials, NAS of Ukraine, Kiev, Ukraine.
    Bushlya, Volodymyr
    Division of Production and Materials Engineering, Lund University, Ole Römers väg 1, Lund, Sweden.
    Understanding wear and interaction between CVD alpha-Al2O3 coated tools, steel, and non-metallic inclusions in machining2022In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 450, p. 128997-, article id 128997Article in journal (Refereed)
    Abstract [en]

    The aluminum oxide-coating on cemented carbide tools used for metal cutting have been regarded as inert during cutting of steels. Because diffusional dissolution is not possible. Chemical degradation of aluminum oxide coatings is often overlooked, especially in the presence of ambient oxygen and non-metallic inclusions. High-pressure diffusion couples, advanced microscopy, and thermodynamics are used to investigate and predict the chemical degradation of aluminum oxide-coated tools. During interactions with steel and different combinations of inclusions with and without ambient oxygen. The results show that alumina is resistant to chemical degra-dation by steel in the absence of oxygen. However, this is not the case when oxygen and non-metallic inclusions are present. These experiments and microscopy together with the thermodynamic calculations allow for the creation of a method and guidelines for chemical wear modeling and steel inclusion engineering when machining with aluminum oxide-coated tools.

  • 5.
    Boor, Katalin
    et al.
    Uppsala Univ, Dept Chem, SE-5120 Uppsala, Sweden..
    Qiu, Ren
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden..
    Forslund, Axel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Backe, Olof
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Lindahl, Erik
    AB Sandvik Coromant, SE-12679 Hagersten, Sweden..
    Halvarsson, Mats
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden..
    Boman, Mats
    Uppsala Univ, Dept Chem, SE-5120 Uppsala, Sweden..
    von Fieandt, Linus
    AB Sandvik Coromant, SE-12679 Hagersten, Sweden..
    Chemical vapor deposition of TiN on a CoCrFeNi multi-principal element alloy substrate2020In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 393, article id 125778Article in journal (Refereed)
    Abstract [en]

    The reactivity of a quaternary multi-principal element alloy (MPEA), CoCrFeNi, as a substrate in thermal halide chemical vapor deposition (CVD) processes for titanium nitride (TiN) coatings was studied. The coatings were deposited at 850 degrees C-950 degrees C using TiCl4, H-2 and N-2 precursors. The coating microstructures were characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM) with energy dispersive X-ray spectroscopy (EDS). Thermodynamic calculations of substrate and coating stability for a gas phase environment of N-2 and H-2 within a temperature range relevant for the experiments showed that Cr is expected to form hexagonal Cr2N and cubic (Ti1-epsilon 1 Cr epsilon 1)N or (Cr1-epsilon 2 Ti epsilon 2)N phases. These phases could however not be discerned in the samples by XRD after the depositions. Cr was detected at the grain boundaries and the top surface by EDS for a sample synthesized at 950 degrees C. Grain boundary and surface diffusion, respectively, were the suggested mechanisms for Cr transport into the coating and onto the top surface. Although thermodynamic calculations indicated that Cr is the most easily etched component of the CoCrFeNi alloy to form gaseous chlorides in similar concentrations to that of the residual Ti-chlorides, no sign of etching were found according to the imaging of the sample cross-sections using SEM and TEM. Cross-section and top surface images further confirmed that the choice of substrate had no significant detrimental influence on the film growth or microstructure.

  • 6.
    Chanouian, Serg
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    The Importance of Mixing Time in Intensely Stirred Metallurgical Reactors: Applied on Decarburization Reactions2023In: Metals, ISSN 2075-4701, Metals, E-ISSN 2075-4701, Vol. 13, no 10, article id 1694Article in journal (Refereed)
    Abstract [en]

    In metallurgical converter processes, numerical modeling is a useful tool for understanding the complexity of the systems. In this paper, we present a practical model that couples fluid dynamics and chemical reactions to explore the impact of mixing time on decarburization. Using computational fluid dynamics (CFD), in this study, we investigate an arbitrary metallurgical reactor with continuous oxygen supply, focusing on the Fe–C–O system. The model employs local equilibrium, a turbulence limiter, and finite volume method for mass, momentum, and energy transfer. Tracer injection points in the gas plume’s rising region exhibit faster mixing, and a comparison of reaction cases reveals distinct decarburization rates based on oxygen injection distribution and the influence of turbulence on reactions. Overall, while mixing time matters, the results show that this system is primarily governed by thermodynamics and oxygen supply, and a 270% increase in mixing time increase had a small impact on the end carbon content.

  • 7.
    Chanouian, Serg
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Pitkala, Jyrki
    Outokumpu Stainless AB.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Modelling Decarburization in the AOD Converter: A Practical CFD-Based Approach with Chemical ReactionsManuscript (preprint) (Other academic)
    Abstract [en]

    Gas blowing technology is widely used in converter steelmaking to homogenize liquid steel and accelerate chemical reactions, with Argon oxygen decarburization (AOD) being the dominant process for stainless steelmaking. Due to the harsh environment, it is advisable to study the phenomenon using small-scale physical models and numerical simulations before conducting industrial-scale trials. This paper presents a practical computational fluid dynamics (CFD) approach for simulating the AOD process, with chemical reactions considered. This approach can simulate the entire process in a reasonable time using a standard workstation. The simulation employs a Finite Volume Method CFD approach to handle mass, momentum and energy transfer, and a local equilibrium assumption is utilized. The study shows that a practical approach can be used to model the initial stage of decarburization in the AOD process with a reduced accuracy in mass transport calculations. The accuracy of the simulation is validated using industrial data, and good agreement is found.

  • 8.
    Forslund, A.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Simulation of reaction-diffusion between substrate and coating during vapor deposition processes2019In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 64, p. 278-283Article in journal (Refereed)
    Abstract [en]

    This work presents simulations of the solid state diffusion and reactions during deposition processes. Two cases are studied where the diffusion in and between coating and substrate is simulated. The processes simulated are in one case directed vapor deposition of Al and Ni on a precoated nickel-base superalloy, and in the other case chemical vapor deposition aluminization of a nickel-base superalloy. The simulations result in composition and phase-fraction profiles, which are presented and compared with experimental composition profiles. The simulation results are generally in good agreement with the experimental profiles.

  • 9.
    Fransson, Erik
    et al.
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden..
    Gren, Martin
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wahnstrom, Goran
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden..
    First-principles modeling of complexions at the phase boundaries in Ti-doped WC-Co cemented carbides at finite temperatures2021In: Physical Review Materials, E-ISSN 2475-9953, Vol. 5, no 9, article id 093801Article in journal (Refereed)
    Abstract [en]

    WC-Co cemented carbides have a unique combination of high hardness and good toughness, making them ideal as tool materials in applications such as metal machining or rock drilling. Dopants are commonly added to retard grain growth and thereby creating a harder material. Thin films with cubic structure have been observed experimentally at phase boundaries between hexagonal WC and fcc Co-rich binder when doping with, e.g., Ti, V, or Cr. These films are generally considered to play a crucial role in the grain growth inhibition effect. Therefore, the thermodynamics of these thin cubic films is important to understand. Here, we construct, using ab initio calculations and modeling, an interfacial phase diagram for thin cubic films in Ti-doped WC-Co. We consider C <-> vacancy and W <-> Ti substitutions by constructing alloy cluster expansions and use Monte Carlo simulations to calculate the configurational free energy. Furthermore, force-constant fitting is used to extract the harmonic free energy for the ground-state structures. Additionally, we use information from thermodynamic databases to couple our atomic-scale calculations to overall compositions of typical WC-Comaterials. We predict that Ti segregates to WC/Co phase boundaries to form thin cubic films of two metallic layer thickness, both at solid-state and liquid-phase sintering temperatures. Furthermore, we predict that these films are stable also for low doping concentrations when no Ti-containing carbide phase precipitates in the material. We show that Ti essentially only segregates to the inner layer of the thin cubic film leaving an almost pure W layer towards Co, an ordering which has been observed in recent experimental high-resolution transmission electron microscopy studies.

  • 10. Gong, Y.
    et al.
    Young, D. J.
    Kontis, P.
    Chiu, Y. L.
    Larsson, H.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermo-Calc Software AB, Råsundavägen 18, SE-169 67 Solna, Sweden.
    Shin, A.
    Pearson, J. M.
    Moody, M. P.
    Reed, R. C.
    On the breakaway oxidation of Fe9Cr1Mo steel in high pressure CO22017In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 130, p. 361-374Article in journal (Refereed)
    Abstract [en]

    Fundamental insights into the mechanism of breakaway oxidation in Fe9Cr1Mo steel are deduced, through advanced characterisation and modelling. Degradation at 600 °C/∼42 bar CO2 for ∼20,000 h is emphasised: conditions relevant to components such as the finned superheater tubes used for advanced gas-cooled nuclear reactors. It is shown that such conditions are sufficient to cause carbon saturation of the metallic substrate, as confirmed by direct observation of extensive carbide precipitation but also numerical analysis of the carbon transport. Thus the observation of graphite precipitation close to the scale/metal interface is rationalised. Nonetheless, the activity of carbon at the scale/metal interface does not reach unity – with respect to graphite – at time zero. A modelling method is proposed which accounts for this kinetic retardation of the attack; this can be used to interpolate across the regimes within which breakaway oxidation is prevalent. It is a plausible model for extrapolation to the lower temperatures relevant to service conditions and is suitable for lifetime estimation – so-called ‘remnant life analysis’ – of such safety-critical components when prone to this form of attack.

  • 11.
    Gong, Yilun
    et al.
    Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England.;Max Planck Inst Eisenforschung, Max Planck Str 1, D-40237 Dusseldorf, Germany..
    Gill, Simon P. A.
    Univ Leicester, Sch Engn, Univ Rd, Leicester LE1, England..
    Yan, Sabrina
    Loughborough Univ, Dept Mat, Epinal Way, Loughborough LE11 3TU, England..
    Higginson, Rebecca
    Loughborough Univ, Dept Mat, Epinal Way, Loughborough LE11 3TU, England..
    Sumner, Joy
    Cranfield Univ, Sch Water Energy & Environm, Coll Rd, Cranfield MK43 0AL, Beds, England..
    Simms, Nigel J.
    Cranfield Univ, Sch Water Energy & Environm, Coll Rd, Cranfield MK43 0AL, Beds, England..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Shin, Aya
    EDF Energy, Barnett Way, Barnwood GL4 3RS, Glos, England..
    Pearson, Jonathan M.
    EDF Energy, Barnett Way, Barnwood GL4 3RS, Glos, England..
    Young, David J.
    Univ New South Wales, Sch Mat Sci & Engn, Sydney, NSW 2052, Australia..
    Atkinson, Colin
    Imperial Coll, Dept Math, London SW7 2BZ, England..
    Cocks, Alan C. F.
    Univ Oxford, Dept Engn Sci, Parks Rd, Oxford OX7 6DP, England..
    Reed, Roger C.
    Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England.;Univ Oxford, Dept Engn Sci, Parks Rd, Oxford OX7 6DP, England..
    Assessment of corrosive attack of Fe9Cr1Mo alloys in pressurised CO2 for prediction of breakaway oxidation2023In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 222, article id 111385Article in journal (Refereed)
    Abstract [en]

    To provide clarity on the poorly-understood mechanism of breakaway oxidation, corrosion of Fe9Cr1Mo steel in pressurised CO2 is quantified and modelled. The temperature range 400-640 degrees C, relevant to nuclear power plants, is emphasised. Attack is in the form of combined oxide scale growth and internal carburisation of the metal. Carbon activity in the metal at its surface exhibits a strong time dependence consistent with the kinetically-limited transport of carbon due to the slow Boudouard reaction. Breakaway is associated with the approach to saturation of the steel with respect to carbon. Diffusion modelling agrees well with steel carbide precipitation observations.

  • 12.
    Graves, Alex
    et al.
    Univ Sheffield, Dept Mat Sci & Engn, Sir Robert Hadfield Bldg,Mappin St, Sheffield S1 3JD, England..
    Salmasi, Armin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Graham, Simon J.
    Univ Sheffield, Dept Mat Sci & Engn, Sir Robert Hadfield Bldg,Mappin St, Sheffield S1 3JD, England..
    Wan, Wei
    AB Sandvik Coromant R&D, SE-12680 Stockholm, Sweden..
    Xiao, Changhong
    AB Sandvik Coromant R&D, SE-12680 Stockholm, Sweden..
    Jackson, Martin
    Univ Sheffield, Dept Mat Sci & Engn, Sir Robert Hadfield Bldg,Mappin St, Sheffield S1 3JD, England..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Norgren, Susanne
    AB Sandvik Coromant R&D, SE-12680 Stockholm, Sweden.;Lund Univ, Dept Mech Engn Sci, Div Prod & Mat Engn, SE-22362 Lund, Sweden..
    An experimental and theoretical investigation on Ti-5553/WC-Co(6%) chemical interactions during machining and in diffusion couples2023In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 516-517, p. 204604-, article id 204604Article in journal (Refereed)
    Abstract [en]

    Chemical interactions that drive crater wear in turning are often studied using diffusion couples where the tool and workpiece are fixed. In contrast, in actual turning, there is a constant supply of new workpiece material at the tool-chip interface. In this work, diffusion simulations of a WC-Co(6%) and Ti-5Al-5V system were conducted, with constant replenishment of titanium at the interface (open system) and a fixed amount of material (closed system). The simulations showed that the formation of W(bcc), ry-phase, and TiC is dependent on the activity of C and the permeability of Co and C in titanium. Scanning and transmission electron microscopy-based techniques were used to analyse a Ti-5Al-5V-5Mo-3Cr and WC-Co(6%) diffusion couple and a worn WC-Co(6%) insert. The sequence of phases in the closed system simulation was similar to that observed in the diffusion couple. The open system simulation indicated that W(bcc) can form at WC-WC boundaries (where Co is low) within the subsurface of a WC-Co(6%) that has adhered titanium, and at the WC/Ti interface. Additionally, high densities of stacking faults and dislocations were found within subsurface WC grains, indicating a significant reduction of the tool's integrity.

  • 13. Graves, Alex
    et al.
    Salmasi, Armin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Graham, Simon
    Wan, Wei
    Xiaoc, Changhong
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Jackson, Martin
    Norgren, Susanne
    An experimental and theoretical investigation on Ti-5553/WC-Co(6%) chemical interactions during machining and in diffusion couplesManuscript (preprint) (Other academic)
  • 14. Hatt, O.
    et al.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Giuliani, F.
    Crawforth, P.
    Wynne, B.
    Jackson, M.
    Predicting Chemical Wear in Machining Titanium Alloys Via a Novel Low Cost Diffusion Couple Method2016In: Procedia CIRP, Elsevier, 2016, p. 219-222Conference paper (Refereed)
    Abstract [en]

    Chemical wear during high speed machining of titanium alloys is a serious problem which affects the surface integrity of both the tool and workpiece. A low cost, novel diffusion couple method is presented which allows for thorough analysis of the tool-workpiece interface at the high temperatures reached during conventional machining operations. X-EDS analysis reveals that no less than seven distinct diffusion zones arise between Ti-6Al-4 V and a WC-Co tool which are home to different phases and reaction species. Loss of cobalt binder coupled with a deficit of carbon results in a brittle η-phase leading to catastrophic fracturing of the tool. DICTRA is employed to thermodynamically model the diffusion mechanisms and verify the X-EDS results.

  • 15.
    Holmström, Erik
    et al.
    Sandvik Coromant R&D, SE-12680 Stockholm, Sweden..
    Lizarraga, Raquel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Linder, David
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Salmasi, Armin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kaplan, Bartek
    Sandvik Coromant R&D, SE-12680 Stockholm, Sweden..
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. ppsala Univ, Div Mat Theory, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    High entropy alloys: Substituting for cobalt in cutting edge technology2018In: Applied Materials Today, ISSN 2352-9407, Vol. 12, p. 322-329Article in journal (Refereed)
    Abstract [en]

    Cemented carbide, also known as hard metal, is one of the most outstanding composite engineering materials since its commercial introduction in the 1920s. The unique combination of strength, hardness and toughness makes cemented carbides highly versatile materials for the most demanding engineering applications. In their simplest form, these materials are composites of tungsten carbide (WC) grains that are cemented with a ductile metallic binder phase, typically cobalt. However, despite the superiority of Co as binder material, there is a long-standing need to find alternative binders due to serious health concerns that have haunted the industry for nearly 80 years. In the present study, we develop a new cemented carbide with a high entropy alloy binder phase (CoCrFeNi) from raw materials to a fully functional, coated and gradient-sintered cutting tool insert. The new hard metal with reduced Co content is designed by using first principles theory and the CALPHAD method. The cutting tool was made by pressing the new hard metal in a standard geometry, sintered to have a thin binder phase enriched surface zone, free from cubic carbides and coated with protective layers of Ti(C,N) and Al2O3. The resulting cutting insert was tested in a real machining operation and compared to a state-of-the-art reference that had Co as binder phase. The cutting tool made of the newly developed cemented carbide has an exceptionally high resistance against plastic deformation at all tested cutting speeds in the machining test, outperforming the reference insert, which shows a linear increase in edge depression when the cutting speed is increased. This result opens up the possibility to utilize the unique properties of high entropy alloys for industrial applications, in particular, as binder phase in new cemented carbides.

  • 16.
    Hulkko, Johan G.
    et al.
    Uppsala Univ, Dept Chem, Angstrom Lab, S-75120 Uppsala, Sweden..
    Qiu, Ren
    Chalmers Univ Technol, Dept Phys, S-41296 Gothenburg, Sweden..
    Forslund, Axel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures. Univ Stuttgart, Inst Mat Sci, D-70569 Stuttgart, Germany..
    Halvarsson, Mats
    Chalmers Univ Technol, Dept Phys, S-41296 Gothenburg, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Boman, Mats
    Uppsala Univ, Dept Chem, Angstrom Lab, S-75120 Uppsala, Sweden..
    Low-pressure CVD of (Ti-x,W1-x)Ny from WF6, TiCl4 and NH32022In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 438, article id 128394Article in journal (Refereed)
    Abstract [en]

    In this work chemical vapour deposited (CVD) coatings of (Tix,W1-x)Ny from TiCl4, WF6, NH3 and Ar were investigated. This coating material has previously been deposited using other vacuum techniques but no publication has so far demonstrated CVD of (Tix,W1-x)Ny. The studied (Tix,W1-x)Ny coatings had a metallic molar ratio (Ti:W) close to 2:1 and 1:1, and were slightly over-stoichiometric with regard to N. The coatings appeared homogeneous and crystallised in a rock salt structure on an alpha-Al2O3 substrate. The cell parameter varied between 4.16 and 4.23 angstrom as a function of the deposition conditions, ranging from a pure TiNx to a pure WNx coating. The texture in the normal direction was (100) for the TiNx and (Tix,W1-x)Ny coatings and (111) for WNx. Electron backscattered diffraction (EBSD) results showed that a strong correlation to the substrate existed but random inplane orientation was also present. The microstructure showed columnar grains with well defined facets growing. Adding a mixture of TiCl4 and WF6 to produce (Tix,W1-x)Ny did increase the grain size significantly when compared to the case when only one metal precursor was present. The down-stream thickness profile, using only WF6 and NH3, displayed mass transport control behaviour, with the coating thickness converging to zero within the deposition zone. Using only TiCl4 on the other hand showed a uniform deposition profile, the signs of a surface kinetics controlled process.

  • 17.
    Jonsson, T.
    et al.
    Environmental Inorganic Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Larsson, Henrik
    Thermo-Calc Software, Råsundavägen 18, SE-169 67 Solna, Sweden.
    Karlsson, S.
    Environmental Inorganic Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Hooshyar, H.
    Environmental Inorganic Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Sattari, M.
    Environmental Inorganic Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Liske, J.
    Environmental Inorganic Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Svensson, J.-E.
    Environmental Inorganic Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Johansson, L.-G.
    Environmental Inorganic Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    High-Temperature Oxidation of FeCr(Ni) Alloys: The Behaviour After Breakaway2017In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 87, no 3-4, p. 333-341Article in journal (Refereed)
    Abstract [en]

    The oxidation of an austenitic FeCr(Ni) steel at 600 C in H2O ?KCl ? O2/H2 ? H2O ? Ar environments is studied up to 168 h. The oxidationbehaviour after ‘‘breakaway’’ is investigated by microstructural investigations, andthermodynamic calculations (Thermo-Calc) on the FeCr(Ni)–O system are used tointerpret the results. The characteristic ‘‘breakaway’’ scale morphology exhibits anoutward-growing iron oxide and a bottom layer consisting of inward-growing spineloxide and reaction zones containing Cr-rich oxide precipitates and Cr-depletedmetal. The equilibrium calculations show that a miscibility gap appears in the FeCrspinel oxide below 665 C influencing the microstructure of the inward-growingscale. Equilibrium calculations on the FeCrNi–O system show that Ni is notexpected to enter the spinel oxide in low oxygen activity conditions, in accordancewith observations

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  • 18.
    Kermanpur, Ahmad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures. Isfahan Univ Technol, Dept Mat Engn, Esfahan 8415683111, Iran..
    Babu, Prasath
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Ryukhtin, Vasyl
    Nucl Phys Inst, CP 130, Husinec Rez 25068, Czech Republic..
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Properties.
    Simulation and experimental analysis of nanoscale precipitation during ageing treatment of laser powder-bed fusion fabricated IN718 Ni-based superalloy2022In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 191, article id 112163Article in journal (Refereed)
    Abstract [en]

    Temporal evolution of the nanoscale disc-shaped gamma';'; (Ni3Nb) and spherical gamma'; (Ni3(Al,Ti)) strengthening pre-cipitates during double-stage ageing treatment of the laser powder-bed fusion (LPBF) fabricated IN718 Ni-based superalloy is studied by thermodynamic-based modeling, electron microscopy, and small-angle neutron scat-tering (SANS). The precipitation kinetics of both gamma';'; and gamma'; particles in the multi-component/multi-phase IN718 alloy system was successfully predicted by the Langer-Schwartz-Kampmann-Wagner approach. The simulated particle size and volume fraction during ageing was validated against electron microscopy and SANS results, respectively. The size and volume fraction of the gamma';'; phase was monotonically increased during the first ageing stage up to about 100 nm and 14%, respectively, but interestingly unchanged during the second stage. On the other hand, the volume fraction of gamma'; phase was sharply increased to about 15% after about 100 s and kept constant until the end of the first ageing stage, where it then decreased to about 7%. The gamma'; particle size monotonically increased up to about 20 nm. According to the determined temporal evolution of the nanoscale precipitates, a shorter ageing treatment of the LPBF IN718 superalloy compared to the conventionally manu-factured alloy could be suggested.

  • 19.
    Larsson, Henrik
    Thermo-Calc Software, Sweden.
    A model for 1D multiphase moving phase boundary simulations under local equilibrium conditions2014In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 47, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Two previously suggested simulation models, for multiphase simulations (Larsson and Engström, 2006;Larsson and Höglund, 2009) and diffusion controlled growth (Larsson and Reed, 2008), respectively, areunified to form a generalized model for 1D simulations of diffusion controlled growth under localequilibrium conditions where multiple phases are allowed on either side of an interface.

  • 20.
    Larsson, Henrik
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    A Random Walk Approach Towards 3D-Modelling of Nucleation, Growth and Coarsening of Precipitates in Steel2003In: IF Steels 2003: international forum for the properties and application of IF steels / [ed] Takechi, H, Iron and Steel Institute of Japan , 2003, p. 268-Conference paper (Other academic)
  • 21.
    Larsson, Henrik
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Internal oxidation processing: New alloys and new simulation techniques2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Nitriding and oxidising treatments of alloys for toolingpurposes have been investigated both experimentally andtheoretically. Specimens prepared by a combination of differentprocessing steps are investigated by light-optical, scanningand transmission electron microscopy and hardness measurments.The bounds of carbon and nitrogen concentration profiles duringnitriding are obtained from simulations using the DICTRA code.As a result, a new processing route to produce oxide-dispersediron-base alloys with large volume fraction of carbides issuggested.

    On the theoretical side the methods based on the random walktechnique have been investigated and developed further. The newmethods have been applied to study a vide range of phenomenae.g. internal oxidation, diffusion in inhomogeneous media,phase transformations and formation of porosity due to theKirkendall effect in welded joints. Probability distributionsare introduced to replace random number generators in order toincrease computational efficiency. A general method to simulatediffusional phase transformations in multicomponent systems isdeveloped and applied to ternary alloys.

     

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  • 22.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermo-Calc Software, Råsundavägen 18, SE-169 67, Solna, Sweden.
    On the use of Boltzmann's transformation to solve diffusion problems2021In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 73, p. 102261-, article id 102261Article in journal (Refereed)
    Abstract [en]

    The use of Boltzmann & rsquo;s transformation to numerically solve diffusion problems using CALPHAD databases is discussed and illustrated with examples. It is shown how it can be applied to problems involving multicomponent, multiphase systems with composition dependent molar volumes. The formation of Kirkendall porosity is also discussed.

  • 23.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Simulation of phase transformations using the lattice-fixed frame of reference2005In: Solid-Solid Phase Transformations in Inorganic Material 2005, Vol 2 / [ed] Howe, JM; Laughlin, DE; Lee, JK; Dahmen, U; Soffa, WA, 2005, p. 789-793Conference paper (Refereed)
    Abstract [en]

    A method for simulating diffusion processes directly in the lattice-fixed frame of reference is described. The method does not require any assumptions regarding the conditions at phase interfaces. An example simulation in the Au-Pt system is presented. A fair agreement with experimental data is obtained.

  • 24.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Agren, J.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Simulation of Coupled Carbonitriding and Internal Oxidation of Steel2017In: HTM-JOURNAL OF HEAT TREATMENT AND MATERIALS, ISSN 1867-2493, Vol. 72, no 1, p. 19-24Article in journal (Refereed)
    Abstract [en]

    Carbonitriding and internal oxidation have been simulated simultaneously using the DICTRA homogenization model. The predicted carbon and nitrogen profiles as well as the oxide and nitride phase fraction profiles agree favourably with experimental data obtained from the literature, though some discrepancies exist. The present approach should be a very useful tool in process control and optimization.

  • 25.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Borgenstam, Annika
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Trans-interface diffusivity in the Fe-Ni system2007In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 56, no 1, p. 61-64Article in journal (Refereed)
    Abstract [en]

    The trans-interface diffusivity in the Fe-Ni system has been estimated by fitting simulations to experimental data. For diffusion across the alpha/gamma phase boundary, the mobility of species divided by an interfacial thickness of 1 nm, M-k/delta, is approximately 5% of the phase interface mobility M-int at 873 K and 15% at 973 K.

  • 26.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Engstrom, A.
    A homogenization approach to diffusion simulations applied to alpha+gamma Fe-Cr-Ni diffusion couples2006In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 54, no 9, p. 2431-2439Article in journal (Refereed)
    Abstract [en]

    The diffusion of Fe, Cr and Ni in one dimension in and between one- and two-phase alpha/gamma regions was simulated using independently assessed thermodynamic and kinetic data. Simulation results compare favourably with experimental Tesults obtained previously by one of the present authors (A. Engstrom). For example, the formation of a gamma layer between an alpha and a gamma + alpha region is correctly predicted. Neither phase interfaces nor individual phases are explicitly considered; instead, locally averaged kinetic properties are used and locally minimized Gibbs energy is assumed.

  • 27.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Erni, R
    Nordberg, L-O
    Ågren, John
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Processing route to an oxide dispersed iron/carbide composite2004In: International journal of refractory metals & hard materials, ISSN 0263-4368, Vol. 22, no 4-5, p. 159-167Article in journal (Refereed)
    Abstract [en]

    A new combination of techniques which should make it possible to produce oxide dispersed alloys by internal oxidation is suggested. The new technique has been used to produce a prototype alloy with a ferritic matrix containing fine (10-20 nm) oxides as well as a large volume fraction of carbides (about 40%). The microstructure indicates that it would be possible to produce an iron-base hard material with improved hot hardness. The technique is based upon an intermetallic starting material and utilises powder metallurgy and attrition ball milling.

     

  • 28.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy. Thermocalc Software, SE-11364 Stockholm, Sweden.
    Höglund, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy. Thermocalc Software, SE-11364 Stockholm, Sweden.
    A scheme for more efficient usage of CALPHAD data in simulations2015In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 50, p. 1-5Article in journal (Refereed)
    Abstract [en]

    A method is suggested that allows thermodynamic data to be dynamically stored and retrieved. The purpose of the method is to reduce computer simulation time when Calphad type databases are being used. Some test simulations are presented and these indicate that simulations can be made to run 5-40 times faster without any significant loss of accuracy.

  • 29.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Höglund, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Multiphase diffusion simulations in 1D using the DICTRA homogenization model2009In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 33, no 3, p. 495-501Article in journal (Refereed)
    Abstract [en]

    A model for multiphase simulations in 1D previously reported in [H. Larsson, A. Engstrom, Acta Mater. 54 (2006) 2431] has been further developed and incorporated in the DICTRA software. The model is based on the assumption of local equilibrium and locally averaged kinetic properties, which computationally transforms the problem into a single-phase diffusion process. The applicability of the model is discussed and example simulations are presented.

  • 30.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy. Thermo-Calc Software, Stockholm, Sweden.
    Jansson, Magnus
    Rate of change at equilibrium2015In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 51, p. 220-223Article in journal (Refereed)
    Abstract [en]

    A general procedure to evaluate derivatives of thermodynamic quantities with respect to equilibrium conditions (external variables, parameters) at equilibrium is outlined. An example calculation is given.

  • 31.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jonsson, T.
    Naraghi, R.
    Gong, Y.
    Reed, R. C.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Oxidation of iron at 600 degrees C - experiments and simulations2016In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176Article in journal (Refereed)
    Abstract [en]

    Pure iron has been oxidized at 600°C and 1bar in dry O2 (oxygen partial pressure 0.05, bal. N2) and the mass gain as well as the thicknesses of the individual oxide phases have been measured. The oxidation process has been simulated using a modified version of the homogenization model as implemented in Dictra; this has helped to rationalize the kinetics of oxide scale formation and in particular the evolution of the hematite (Fe2O3), magnetite (Fe3O4), and wustite (FeO) which form. Independently assessed thermodynamic and kinetic Calphad databases are needed for the calculations; details of these are given. Reasonable agreement between simulation results and experimental data is obtained, though it is concluded that the large influence of grain boundary diffusion on the oxidation rate needs further consideration.

  • 32.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Reed, R. C.
    On the numerical simulation of diffusion-controlled reactions under local equilibrium conditions2008In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 56, no 15, p. 3754-3760Article in journal (Refereed)
    Abstract [en]

    To estimate the interfacial velocity in a multicomponent moving boundary problem, existing procedures require an interative technique too be used if a sharp interface methods is employed. The need to use an interactive technique can cause convergence problems; these become more frequent as more components are added. In this paper, two new methods are suggested which allow the velocity of a phase interface to be evaluated directly from the fluxes of the components Wider the assumption of local equilibrium. The methods assume that the interface has a fixed width in which the incoming and outgoing components are distributed in a way that moves the interface while maintaining local equilibrium. Example simulations are presented and results are ill good agreement with established front-tracking simulation software (DICTRA) moreover. the superior convergence of the new methods is demonstrated .

  • 33.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Schwind, M
    Ågren, John
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    A cellular automata treatment of internal oxidation2000In: Proc. Int. Conf. Mass and Charge Transport in Inorganic Materials: Fundamentals to Devices, Lido di Jesolo, Italy, 2000 / [ed] P Vincenzini, V Buscaglia, Faenza (Ravenna): Techna , 2000, p. 647-652Conference paper (Other academic)
  • 34.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Strandlund, H.
    Hillert, Mats
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Unified treatment of Kirkendall shift and migration of phase interfaces2006In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 54, no 4, p. 945-951Article in journal (Refereed)
    Abstract [en]

    A recent treatment of diffusion in a lattice-fixed frame of reference, which can predict the Kirkendall shift, is modified to be applicable also to the migration of phase interfaces. The net flux across a reference point in the lattice, yielding the Kirkendall shift, as well as the net flux across a phase interface, yielding its migration, are obtained from the same flux equation. Numerical calculations are presented and demonstrate that the method gives expected results. The strength of the method is that it is not based on the assumption of local equilibrium and it is capable of automatically yielding close to local equilibrium conditions except at high supersaturations. There it describes an increasing deviation from local equilibrium as the initial alloy composition is moved inside the one-phase field for the new phase. The interaction of a migrating phase interface and Kirkendall markers is also illustrated.

  • 35.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Ågren, John
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    A random-walk approach to diffusion controlled growth2003In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 49, no 6, p. 521-526Article in journal (Refereed)
    Abstract [en]

    The new method does not require formulation of any special conditions at the moving phase interface. Although only binary systems are treated at present an extension to any number of components seems straightforward. A good agreement with conventional front tracking techniques (DICTRA) is found.

  • 36.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Ågren, John
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    A random-walk approach to diffusion controlled growth II: A distribution function solution2004In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 51, no 2, p. 137-140Article in journal (Refereed)
    Abstract [en]

    Earlier work on simulations of diffusion controlled transformations based on a random-walk technique is extended; a random-walk simulation of a transformation in a ternary system and a new method based on distribution functions are presented. As before, no special assumption regarding the state of the phase interface is required.

  • 37.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Ågren, John
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    A random-walk investigation of the diffusive properties of inhomogenous mediaIn: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550Article in journal (Refereed)
  • 38.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Combined probability distributions of random-walks: A new method to simulate diffusion processes2005In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 34, no 3, p. 254-263Article in journal (Refereed)
    Abstract [en]

    Two related methods to simulate diffusion processes are presented. Both are based on conceiving diffusion as a random-walk process. Several example simulations are presented: single phase diffusion couples, diffusion controlled growth and prediction of Kirkendall porosity. Comparisons with experimental results and simulation software based on established technique (DICTRA) show good agreement with results obtained from the presented models.

  • 39.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments (pre-2005), Metallurgy.
    Ågren, John
    KTH, Superseded Departments (pre-2005), Metallurgy.
    Gas nitriding of high vanadium steels: Experiments and simulations2004In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 35A, no 9, p. 2799-2802Article in journal (Refereed)
    Abstract [en]

    Four experimental high vanadium alloys were gas nitrided in an ammonia-nitrogen atmosphere. The microstructure and concentration gradients have been investigated by means of several techniques. The nitriding process has been tentatively simulated using the DICTRA software. A precise process simulation does not seem possible at present; the reason for this is discussed. Instead, bounds for the carbon and nitrogen concentration profiles were obtained by applying different simulation conditions.

  • 40. Morral, J. E.
    et al.
    Pan, X. M.
    Zhou, N.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Wang, Y. Z.
    Singularities in multiphase diffusion couples2008In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 58, no 11, p. 970-972Article in journal (Refereed)
    Abstract [en]

    Singularities are not normally expected in diffusion couple data; however, they can occur in certain multiphase concentration profiles and diffusion paths. The following work reviews the theoretical reason why singularities form and gives two different computer simulations that support the theoretical predictions. In addition, a correction is given to a previous paper in which artifacts created by modeling software were inadvertently reported as diffusional singularities.

  • 41.
    Mukherjee, Deepjyoti
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Forslund, Axel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Höglund, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Ruban, Andrei V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Towards predictive simulations of spinodal decomposition in Fe-Cr alloys2022In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 202, article id 110955Article in journal (Refereed)
    Abstract [en]

    Simulations of spinodal decomposition in an Fe-36 wt%Cr alloy at 773 K are performed by solving the non -linear Cahn-Hilliard equation, and the results are compared with atom probe tomography measurements. The influence of gradient energy coefficient, atomic mobilities and initial structure on the kinetics of spinodal decomposition is studied. It is shown that a proper initial structure, accounting for the thermal history above the miscibility gap, is crucial and enables predictive simulations of spinodal decomposition in Fe-Cr alloys.

  • 42.
    Mukherjee, Deepjyoti
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Phase field modelling of diffusion induced grain boundary migration in binary alloys.2020In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 184, article id 109914Article in journal (Refereed)
    Abstract [en]

    The Phase field method has been used to study Diffusion Induced Grain boundary Migration (DIGM) in binary alloys. Simulations are performed for a simple hypothetical binary substitutional solid solution. The model is developed by taking into account the elastic interactions arising due to changes in concentration across a grain boundary when solutes are diffusing along the grain boundary. This gives a coupling term in the Gibbs energy functional that acts as a driving force for grain boundary migration. Two different kinds of coupling terms are studied: one acting on both the abutting grains and the other acting on only one grain. The former gives a freedom of choice as to in which direction the grain boundary will move, and is considered more general, whereas the latter only moves in one direction, regardless of the shape of the grain boundary. The results from the model are in qualitative agreement with previous experimental studies.

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  • 43.
    Mukherjee, Deepjyoti
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Phase Field Study of Discontinuous Precipitation in a Miscibility Gap SystemManuscript (preprint) (Other academic)
    Abstract [en]

    A phase field model is developed to study the discontinuous (cellular) precipitation(DP) in a hypothetical A-B miscibility gap system. The model employs an interaction energy term which couples the mole fraction (xA) and the phase field variable (Φ) to study the mechanism behind the precipitation process. The term was used recently to model diffusion induced grain boundary migration in a hypothetical binary system Ref. Mukherjee et al. 2020. The interaction term suggests that strain energy develops after nucleation of DP strands at grain boundaries. The strands are observed to grow behind a moving grain boundary which favours one of the grains, thereby, taking the same orientation of the grain behind the growth front. The factors such as gradient energy coefficient (κ), the prefactor (K) from Hillert's expression for strain energy Ref. Hillert 1983, interfacial mobility (MΦ) and interface diffusion (F) are altered to study their influence on lamellar spacing.

  • 44.
    Mukherjee, Deepjyoti
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Simulating diffusion induced grain boundary migration in binary Fe-ZnManuscript (preprint) (Other academic)
    Abstract [en]

    A recently developed phase-field model for simulating diffusion-induced grain boundary migration (DIGM) is applied to binary Fe--Zn. The driving force for the boundary migration is assumed to come from the coherency strain energy mechanism suggested by Sulonen. The effect of the angle of the grain boundary with the surface on the velocity of the boundary migration is studied in detail. The simulation results compare favorably with experimental observations, such as the oscillatory motion of the grain boundary, velocity of the moving grain boundary during DIGM, and the maximum value of mole fraction of Zn at the surface after 20~h of heat treatment.

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  • 45.
    Mukherjee, Deepjyoti
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Simulating Diffusion Induced Grain Boundary Migration in Binary Fe-Zn2022In: Metals, ISSN 2075-4701, Vol. 12, no 10, article id 1632Article in journal (Refereed)
    Abstract [en]

    A recently developed phase-field model for simulating diffusion-induced grain boundary migration (DIGM) is applied to binary Fe-Zn. The driving force for the boundary migration is assumed to come from the coherency strain energy mechanism suggested by Sulonen. The effect of the angle of the grain boundary with the surface on the velocity of the boundary migration is studied in detail. The simulation results compare favorably with experimental observations, such as the oscillatory motion of the grain boundary, velocity of the moving grain boundary during DIGM, and the maximum value of mole fraction of Zn at the surface after 20 h of heat treatment.

  • 46.
    Mukherjee, Deepjyoti
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Dahlberg, Carl F. O.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Phase field modeling of discontinuous precipitation in (Ti,Zr)CManuscript (preprint) (Other academic)
    Abstract [en]

    Discontinuous precipitation at high temperatures in (Ti,Zr)C was modeled using the phase field method. The modelling was based on previous treatments of diffusion induced grain boundary migration and spinodal decomposition. A fair agreement with experimental observations was obtained. However, a more refined treatment of the effect of strain energy is left for future work.

  • 47.
    Olsson, Mike
    et al.
    Lund Univ, Div Prod & Mat Engn, Box 118, Lund 22100, Sweden..
    Lenrick, Filip
    Lund Univ, Div Prod & Mat Engn, Box 118, Lund 22100, Sweden..
    M'Saoubi, Rachid
    Lund Univ, Div Prod & Mat Engn, Box 118, Lund 22100, Sweden.;Seco Tools AB, R&D Mat & Technol Dev, Fagersta 73782, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Markström, Andreas
    Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Petrusha, Igor
    NAS Ukraine, Inst Superhard Mat, Kiev, Ukraine..
    Stahl, Jan-Eric
    Lund Univ, Div Prod & Mat Engn, Box 118, Lund 22100, Sweden..
    Bushlya, Volodymyr
    Lund Univ, Div Prod & Mat Engn, Box 118, Lund 22100, Sweden..
    Study of wear mechanisms of cemented carbide tools during machining of single-phase niobium2020In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 450, article id 203244Article in journal (Refereed)
    Abstract [en]

    In particle accelerator facilities, single-phase niobium is used in superconducting accelerator components. Machining induced surface quality of such components is strongly connected to the functionality of accelerators. In this study, tool wear development and its influence on the surface quality of Nb workpiece have been investigated in longitudinal turning. Uncoated cemented carbide cutting tools were used under finishing conditions (cutting speed v

  • 48.
    Rosenblad, Louise
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Staf, Hjalmar
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics. Sandvik Coromant AB, R&D, SE-12680 Vastberga, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    An Experimental Investigation of the Solid State Sintering of Cemented Carbides Aiming for Mechanical Constitutive Modelling2023In: Crystals, ISSN 2073-4352, Vol. 13, no 6, article id 978Article in journal (Refereed)
    Abstract [en]

    The densification of cemented carbides during sintering was studied using an existing constitutive model based on powder particle size and material composition. In the present analysis, we study how well the constitutive model can capture the experimental results of a dilatometer test. Three experiments were performed, where the only difference was the transition between the debinding and sintering process. From magnetic measurements, it is concluded that the carbon level in the specimen is affected by changes to the experimental setup. It is shown, using parameter adjustments, that the constitutive model is more suited for a certain experimental setup and carbon level, which is a limitation of the model. In order to capture the mechanical behaviour under different experimental conditions, further constitutive modelling relevant to the carbon level is recommended.

  • 49.
    Rosenblad, Louise
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Staf, Hjalmar
    Sandvik Coromant AB, Sweden.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Constitutive Modelling Of Solid State Sintering Of Cemented Carbides2022In: World PM 2022 Congress Proceedings, European Powder Metallurgy Association (EPMA) , 2022Conference paper (Refereed)
    Abstract [en]

    From a previously developed constitutive model for cemented carbide, the powder size- and configuration can be used to simulate the densification during the sintering process. However, small differences in experimental execution cannot be accounted for in the simulation, making the model sensitive. Here, we study how well the developed constitutive model can capture the experimental results of a dilatometer test. Three different experiments were performed where the only difference was the transition between the debinding and sintering process. From parameter adjustments, it is seen that the constitutive model is more suited for a certain experimental setup, which is a limitation of the model.

  • 50.
    Rosenblad, Louise
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Staf, Hjalmar
    Sandvik Coromant AB, R&D, SE-12680 Stockholm, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Parametric dependency of a constitutive model describing solid state sintering of cemented carbides2022In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 403, p. 117407-, article id 117407Article in journal (Refereed)
    Abstract [en]

    This study focuses on an inverse modelling approach, using FEM to simulate the sintering of WC-Co powder using a continuum model. From a previously developed constitutive model of cemented carbide, the dependency of the material parameters is investigated in a sensitivity study. A value of sensitivity is assigned to all the material parameters and calculated at different steps in the sintering process, which represent its importance for capturing the shrinkage during sintering. The approach is that only the more sensitive parameters should be fitted when changing experimental setup or material composition, leaving the less important parameters constant, resulting in fewer tests and iterations. This approach is tested in an optimization of WC-Co powder sintering cycle, where the shrinkage curve is experimentally determined. It is concluded that some of the material parameters play a minor role in the modelling and could be set as constants in an optimization. The constitutive material model alone is unable to capture all features that appeared in the shrinkage curve during the experiment. Improvements of the model are discussed. An additional investigation, performed without heating rate dependency, shows that the remaining material parameters could compensate for the omitted heating rate for a known sintering cycle without losing accuracy.

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