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  • 1.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Materials Technology, Sandviken, Sweden.
    Eriksson, Robert
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan J.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Characterization of austenitic stainless steels deformed at elevated temperature2017In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48A, no 10, p. 4525-4538Article in journal (Refereed)
    Abstract [en]

    Highly alloyed austenitic stainless steels are promising candidates to replace more expansive nickel-based alloys within the energy-producing industry. The present study investigates the deformation mechanisms by microstructural characterisation, mechanical properties and stress-strain response of three commercial austenitic stainless steels and two commercial nickel-based alloys using uniaxial tensile tests at elevated temperatures from 400 C up to 700 C. The materials showed different influence of temperature on ductility, where the ductility at elevated temperatures increased with increasing nickel and solid solution hardening element content. The investigated materials showed planar dislocation driven deformation at elevated temperature. Scanning electron microscopy showed that deformation twins were an active deformation mechanism in austenitic stainless steels during tensile deformation at elevated temperatures up to 700 C.

  • 2.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Materials Technology,Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Creep and Fatigue Interaction Behavior in Sanicro 25 Heat Resistant Austenitic Stainless Steel2016In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 69, no 2, p. 337-342Article in journal (Refereed)
    Abstract [en]

    Sanicro 25 is a newly developed advanced high strength heat resistant austenitic stainless steel. The material shows good resistance to steam oxidation and flue gas corrosion, and has higher creep rupture strength than other austenitic stainless steels available today. It is thus an excellent candidate for superheaters and reheaters for advanced ultra-super critical power plants with efficiency higher than 50 %. This paper provides a study on the creep–fatigue interaction behavior of Sanicro 25 at 700 °C. Two strain ranges, 1 and 2 %, and two dwell times, 10 and 30 min, were used. The influences of dwell time on the cyclic deformation behavior and life has been evaluated. Due to stress relaxation the dwell time causes a larger plastic strain range compared to the tests without dwell time. The results also show that the dwell time leads to a shorter fatigue life for the lower strain range, but has no or small effect on the life for the higher strain range. Fracture investigations show that dwell times result in more intergranular cracking. With the use of the electron channeling contrast imaging technique, the influences of dwell time on the cyclic plastic deformation, precipitation behavior, recovery phenomena and local plasticity exhaustion have also been studied.

  • 3.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Damage and Fracture Behaviours in Advanced Heat Resistant Materials During Slow Strain Rate Test at High Temperature2013Conference paper (Other academic)
    Abstract [en]

    As a renewable energy resource, biomass or biomass co-firing in coal-fired power plants with high efficiency are desired which corresponding to elevated temperature and high pressure. An upgrade of the material performance to austenitic stainless steels is therefore required in order to meet the increased demands due to the higher temperature and the more corrosive environment. These materials suffer from creep and fatigue damage during the service. In this study, these behaviours are evaluated using slow strain rate testing (SSRT) with strain rate down to 1*10-6/s at temperature up to 700°C. The influence of temperature and strain rate on strength and ductility in one austenitic stainless steel and one nickel base alloys are investigated. The damage and fracture due to the interaction between moving dislocations and precipitates are studied using electron channelling contrast imaging (ECCI) and electron backscattering diffraction (EBSD). The deformation and damage mechanisms active during SSRT are essentially the same as under creep. The influence of dynamic strain ageing (DSA) phenomena that appears in the tested temperature and strain rate regime is also discussed, DSA is intensified by increased temperature and decreased strain rate.

  • 4.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Damage and Fracture Behaviours in Aged Austentic Materials During High-Temperature Slow Strain Rate Testing2014Conference paper (Refereed)
    Abstract [en]

    Biomass power plants with high efficiency are desired as a renewable energy resource. High efficiency can be obtained by increasing temperature and pressure. An upgrade of the material performance to high temperature material is therefore required in order to meet the increased demands due to the higher temperature and the more corrosive environment. In this study, the material’s high-temperature behaviours of AISI 304 and Alloy617 under slow deformation rate are evaluated using high-temperature long-term aged specimens subjected to slow strain rate tensile testing (SSRT) with strain rates down to 10-6/s at 700°C. Both materials show decreasing stress levels and elongation to fracture when tensile deformed using low strain rate and elevated temperature. At high-temperature and low strain rates cracking in grain boundaries due to larger precipitates formed during deformation is the most common fracture mechanism.

  • 5.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Deformation and damage behaviours of austenitic alloys in the dynamic strain ageing regimeManuscript (preprint) (Other academic)
    Abstract [en]

    Deformation and damage behaviours influenced by dynamic strain ageing (DSA) in three austenitic stainless steels and two nickel-base alloys have been investigated using tensile tests at elevated temperatures. The deformation and damage behaviours have been analysed using electron channeling contrast imaging and electron backscatter diffraction. The results from this study show that DSA not always reduce ductility, in fact for some materials the ductility can increase in the DSA regime. This is attributed to the formation of nano twins by DSA stimulated twinning induced plasticity. Damage mechanisms due to DSA were also investigated and discussed.

  • 6.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Deformation behaviour in advanced heat resistant materials during slow strain rate testing at elevated temperature2014In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 4, no 041004Article in journal (Refereed)
    Abstract [en]

    In this study, slow strain rate tensile testing at elevated temperature is used to evaluate the influence of temperature and strain rate on deformation behaviour in two different austenitic alloys. One austenitic stainless steel (AISI 316L) and one nickel-base alloy (Alloy 617) have been investigated. Scanning electron microscopy related techniques as electron channelling contrast imaging and electron backscattering diffraction have been used to study the damage and fracture micromechanisms. For both alloys the dominante damage micromechanisms are slip bands and planar slip interacting with grain bounderies or precipitates causing strain concentrations. The dominante fracture micromechanism when using a slow strain rate at elevated temperature, is microcracks at grain bounderies due to grain boundery embrittlement caused by precipitates. The decrease in strain rate seems to have a small influence on dynamic strain ageing at 650°C.

  • 7.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of deformation rate on mechanical response of an AISI 316L austenitic stainless steel2014In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 922, p. 49-54Article in journal (Refereed)
    Abstract [en]

    Austenitic stainless steels are often used for components in demanding environment. These materials can withstand elevated temperatures and corrosive atmosphere like in energy producing power plants. They can be plastically deformed at slow strain rates and high alternating or constant tensile loads such as fatigue and creep at elevated temperatures. This study investigates how deformation rates influence mechanical properties of an austenitic stainless steel. The investigation includes tensile testing using strain rates of 2*10-3/ and 10-6/s at elevated temperatures up to 700°C. The material used in this study is AISI 316L. When the temperature is increasing the strength decreases. At a slow strain rate and elevated temperature the stress level decreases gradually with increasing plastic deformation probably due to dynamic recovery and dynamic recrystallization. However, with increasing strain rate elongation to failure is decreasing. AISI 316L show larger elongation to failure when using a strain rate of 10-6/s compared with 2*10-3/s at each temperature. Electron channelling contrast imaging is used to characterize the microstructure and discuss features in the microstructure related to changes in mechanical properties. Dynamic recrystallization has been observed and is related to damage and cavity initiation and propagation.

  • 8.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of Dynamic Strain Ageing on Damage in Austenitic Stainless Steels2012Conference paper (Other academic)
  • 9.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, sweden.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of High Temperature Ageing on the Toughness of Advanced Heat Resistant Materials2013Conference paper (Refereed)
    Abstract [en]

    Advanced biomass, biomass co-firing in coal-fired and future advanced USC coal-fired power plants with high efficiency require the materials to be used at even higher temperature under higher pressure. The reliability and integrity of the material used are therefore of concern. In this study, the influence of ageing at temperatures up to 700°C for up to 3 000 hours on the toughness of two advanced heat resistant austenitic steels and one nickel alloy are investigated. The influence on toughness due to differences in the chemical composition as well as the combined effect of precipitation and growth of the precipitates has been analysed by using SEM techniques. The fracture mechanisms that are active for the different ageing treatments are identified as a function of temperature and time. Local approach methods are used to discuss the influence of the precipitation and growth of precipitates on the toughness or fracture in  the different aged materials.

  • 10.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Long Term High-Temperature Environmental Effect on Impact Toughness in Austenitic Alloys2015In: / [ed] Key Engineering Materials Vol 627 (2015),pp 205-208., 2015, p. 205-308Conference paper (Refereed)
  • 11.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Strategy research, SE-81181 Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Mechanical behaviors of alloy 617 with varied strain rates at high temperatures2014In: THERMEC 2013, Trans Tech Publications Ltd , 2014, Vol. 783-786, p. 1182-1187Conference paper (Refereed)
    Abstract [en]

    Nickel base alloys due to their high performances have been widely used in biomass and coal fired power plants. They can undertake plastic deformation with different strain rates such as those typically seen during creep and fatigue at elevated temperatures. In this study, the mechanical behaviors of Alloy 617 with strain rates from 10-2/s down to 10-6/s at temperatures of 650C and 700C have been studied using tensile tests. Furthermore, the microstructures have been investigated using electron backscatter detection and electron channeling contrast imaging. At relatively high strain rate, the alloy shows higher fracture strains at these temperatures. The microstructure investigation shows that it is caused by twinning induced plasticity due to DSA. The fracture strain reaches the highest value at a strain rate of 10-4/s and then it decreases dramatically. At strain rate of 10-6/s, the fracture strain at high temperature is now smaller than that at room temperature, and the strength also decreases with further decreasing strain rate. Dynamic recrystallization can also be observed usually combined with crack initiation and propagation. This is a new type of observation and the mechanisms involved are discussed. © (2014) Trans Tech Publications, Switzerland.

  • 12.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Mechanical Behaviours of Alloy 617 with Varied Strain Rate at High Temperatures2014In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 783-786, p. 1182-1187Article in journal (Refereed)
    Abstract [en]

    Nickel-base alloys due to their high performances have been widely used in biomass and coal fired power plants. They can undertake plastic deformation with different strain rates such as those typically seen during creep and fatigue at elevated temperatures. In this study, the mechanical behaviours of Alloy 617 with strain rates from 10-2/s down to 10-6/s at temperatures of 650°C and 700°C have been studied using tensile tests. Furthermore, the microstructures have been investigated using electron backscatter detection and electron channeling contrast imaging. At relatively high strain rate, the alloy shows higher fracture strains at these temperatures. The microstructure investigation shows that it is caused by twinning induced plasticity due to DSA. The fracture strain reaches the highest value at a strain rate of 10-4/s and then it decreases  dramatically. At strain rate of 10-6/s, the fracture strain at high temperature is now smaller than that at room temperature, and the strength also decreases with further decreasing strain rate. Dynamic recrystallization can also be observed usually combined with crack initiation and propagation. This is a new type of observation and the mechanisms involved are discussed.

  • 13.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Eriksson, Robert
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Siemens Industrial Turbomachinery AB, Berlin.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Högberg, Jan
    AB Sandvik Materials Technology R&D Center Sandviken.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Local Surface Phase Stability During Cyclic Oxidation Process2017In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 879, p. 855-860Article in journal (Refereed)
  • 14.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Eriksson, Robert
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Influence of Cyclic Oxidation in Moist Air on Surface Oxidation-Affected Zones2017Conference paper (Refereed)
  • 15.
    Calmunger, Mattias
    et al.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials.
    Eriksson, Robert
    Siemens AG, Huttenstr. 12, 10553 Berlin, Germany.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Surface Phase Transformation in Austenitic Stainless Steel Induced by Cyclic Oxidation in Humidified Air2015In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 100, p. 524-534Article in journal (Refereed)
    Abstract [en]

    The formation of α’ martensite at the surface of an AISI 304 stainless steel subjected to cyclic heating in humidified air is reported. The α’ martensite formed during the cooling part of the cyclic tests due to local depletion of Cr and Mn and transformed back to austenite when the temperature again rose to 650 °C. The size of the α’ martensite region increased with increasing number of cycles. Thermodynamical simulations were used as basis for discussing the formation of α’ martensite. The effect of the α’ martensite on corrosion is also discussed.

  • 16.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Materials Technology, Sandviken, Sweden.
    Characterisation of creep deformation during slow strain rate tensile testing2015Manuscript (preprint) (Other academic)
    Abstract [en]

    The strain-rate dependent deformation of the superalloy Haynes 282 during slow strain-rate tensile testing (SSRT) at 700 C has been investigated. The stress-strain response is remarkably well described by a simple constitutive model over a wide range of different strain-rates. The microstructure development is characterised and related to the influence of both strainrate dependent and independent deformation. Damage and cracking similar to what has been observed previously during conventional creep testing of Haynes 282 was found and explained. The model and the microstructure investigations show that the deformation and damage mechanisms during SSRT are essentially the same as under creep.

  • 17.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Advanced Microstructure Studies of an Austenitic Material Using EBSD in Elevated Temperature In-Situ Tensile Testing in SEM2014Conference paper (Refereed)
    Abstract [en]

    In this study an advanced method for investigation of the microstructure such as electron backscatter diffraction (EBSD) together with in-situ tensile test in a scanning electron microscope (SEM) has been used at room temperature and 300°C. EBSD analyses provide information about crystallographic orientation in the microstructure and dislocation structures caused by deformation. The in-situ tensile tests enabled the same area to be investigated at different strain levels. For the same macroscopic strain values a lower average misorientation in individual grains at elevated temperature indicates that less residual strain at grain level are developed compared to room temperature. For both temperatures, while large scatters in grain average misorientation are observed for grains of similar size, there seems to be a tendency showing that larger grains may accumulate somewhat more strains.

  • 18.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Advanced Heat Resistant Austenitic Stainless Steels and Composite Tube Materials for High Efficient Clean Energy Production2013Conference paper (Refereed)
  • 19.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Mat Technology, Sweden.
    Analysis of microdamage in a nickel-base alloy during very high cycle fatigue2016In: Fatigue & Fracture of Engineering Materials & Structures, ISSN 8756-758X, E-ISSN 1460-2695, Vol. 39, no 6, p. 712-721Article in journal (Refereed)
    Abstract [en]

    Fatigue damage in a metallic material during very high cycle fatigue can strongly be correlated to the microstructure. This paper provides a review and a discussion on the micro damage behaviours in a nickel-base alloy during very high cycle fatigue using microplasticity and material mechanics. The results show that cyclic plastic deformation in this material can occur very locally even with an applied stress that is much lower than the yield strength. The fatigue damage occurs mainly at grain or twin boundaries because of local impingement and interaction of slip bands and these boundaries. The crystallographic properties, Schmid factors and orientations of grain and boundaries play very important roles to the fatigue damage. Subsurface fatigue crack initiation in the matrix is one of very high cycle fatigue mechanisms. Twinning and detwinning can also occur during the very high cycle fatigue process.

  • 20.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Damage Behaviors at Twin and Grain Boundary in Alloy 690 Material in Very High Cycle Fatigue Regime2015Conference paper (Refereed)
  • 21.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Damage Mechanism of Low Cycle Fatigue in an Advanced Heat Resistant Austenitic Stainless Steel at High Temperature2014In: Procedia Materials Science, ISSN 2211-8128, Vol. 3, p. 1754-1759Article in journal (Refereed)
    Abstract [en]

    Sandvik Sanicro 25 is a newly developed heat resistant austenitic stainless steel grade for the next generation of coal fired advanced ultra-super critical (AUSC) power plants. In this paper, low cycle fatigue behavior and damage mechanisms of the material were studied. The low cycle fatigue test was performed in air at room temperature, 600 °C to 700 °C. The microstructures were studied using electron back scatter diffraction and electron channeling contrast image techniques. At room temperature, the material shows a conventional hardening and softening behavior as most metal materials. At high temperatures, however, it shows only a cyclic hardening behavior. Dynamic strain ageing is found to be one of the mechanisms. The damage and fatigue crack initiation mechanisms due to cyclic loading at different temperatures and loading conditions have been identified. The interactions between dislocations or slip bands with grain boundary or twin boundary are the main damage mechanism at low temperature or at high temperature with large strain amplitudes. Strain localization due to dislocation slipping is the main mechanism for the fatigue damage in grains.

  • 22.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Fatigue Crack Initiation in Metallic Matrix2014In: TMS 2014 SUPPLEMENTAL PROCEEDINGS, John Wiley & Sons, 2014, p. 647-654Conference paper (Refereed)
    Abstract [en]

    This paper will provide a study on the behaviors of fatigue crack initiation in metal matrix in five metallic materials using very high cycle fatigue testing and electron microscopy with electron backscatter diffraction and electron channeling contrast technique. The damage and crack initiation mechanisms in metal matrix have been focused. It shows that straining in these materials during the fatigue process was highly localized. This strain localization has led to the damage or fatigue crack initiation at grain boundaries or twin boundaries by impingement cracking. High strain localization causes dislocation accumulation during each cyclic straining and consequently the formation of local "fine grain zone" that increases the local damage by plasticity exhaustion. This can cause the formation of fatigue crack origin in the matrix. Strain localization and local plasticity exhaustion can be used to explain this phenomenon.

  • 23.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Low Cycle Fatigue Behavior and Mechanism of Newly Developed Advanced Heat Resistant Austenitic Stainless Steels at High Temperature2014In: 11th International Fatigue Congress, Trans Tech Publications Inc., 2014, Vol. 891-892, p. 377-382Conference paper (Refereed)
    Abstract [en]

    Austenitic stainless steel grade UNS S31035 (Sandvik Sanicro® 25) has been developed for the next generation of 700°C A-USC power plant. This paper will mainly focus on the study of low cycle fatigue behavior and damage mechanisms of the material at room temperature, 600C to 700C by using electron back scatter diffraction and electron channeling contrast image techniques. At room temperature, the material shows a hardening and softening behavior as usual. At high temperature, however, it shows only a cyclic hardening behavior. Dynamic strain ageing can be one of the mechanisms. The damage and fatigue crack initiation mechanisms due to cyclic loading at different temperatures and loading conditions have been identified. The interactions between dislocations or slip bands with grain boundary or twin boundary are the main damage mechanism at low temperature or at high temperature with large strain amplitudes. Strain localization due to dislocation slipping is the main mechanism for the damage in grain.

  • 24.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Micro Heterogenous Fatigue Cracking Behavior in Dual Phase Materials2013Conference paper (Refereed)
  • 25.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    On Fatigue Crack Initiaition in th Matrix in Very High Cycle Fatigue Regime2013Conference paper (Refereed)
  • 26.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Subsurface Non Defect Fatigue Crack Origin and Local Plasticity Exhaustion2013Conference paper (Refereed)
  • 27.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Andersson, Marcus
    Sandvik Materials Technology, Sandviken, Sweden.
    Secondary Hardening Behavior in Super Duplex Stainless Steels during LCF in Dynamic Strain Ageing Regime2013In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 55, p. 123-127Article in journal (Refereed)
    Abstract [en]

    Cyclic deformation behaviors in five modified duplex stainless steel S32705 grades have been studied at 20 °C, 200 °C, 250° and 350 °C. The influence of temperature and nitrogen concentration on the occurrence of the second hardening phenomenon, in the stress response curve was focused. An increase in nitrogen concentration can have a positive effect on dynamic strain ageing by increasing the first hardening and also the second hardening behavior during cyclic deformation. Furthermore, an increase in nitrogen concentration in the super duplex stainless steel increases the fatigue life in the strain ageing temperature range. The occurrence of strain ageing in duplex stainless steel has greatly changed dislocation structures. The formation of irreversible dislocation structures and stacking faults can contribute to the formation of second hardening in the stress response curve.

  • 28.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Boström, Magnus
    Sandvik Materials Technology, Sandviken, Sweden.
    Olaison, Magnus
    Sandvik Materials Technology, Sandviken, Sweden.
    Forsberg, Urban
    Sandvik Materials Technology, Sandviken, Sweden.
    Creep and LCF Behaviors of Newly Developed Advanced Heat Resistant Austenitic Stainless Steel for A-USC2013In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 55, p. 232-239Article in journal (Refereed)
    Abstract [en]

    Austenitic stainless steel grade UNS S31035 (Sandvik Sanicro® 25) has been developed for use in super-heaters and reheaters in the next generation of A-USC power plants. This new grade shows very good resistances to steam oxidation and hot corrosion, and higher creep rupture strength than other austenitic stainless steels available today. This makes it an interesting alternative for super-heaters and reheaters in future high-efficient coal fired boilers. This paper will mainly focus on the study of the creep and LCF behavior of the material at temperatures from 600 °C to 750 °C by using TEM and ECCI. The mechanisms at different temperatures and loading conditions have been identified. The interactions between dislocations and precipitates and their contribution to the creep rupture strength have been discussed. In this paper, different models have been used to evaluate the long-term creep behavior of the grade. A creep rupture strength near 100 MPa at 700 °C for 100 000 h has been predicted.

  • 29.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Materials Technology, Strategy research, Sandviken, Sweden.
    Calmunger, Mattias
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Odqvist, Joakim
    Sandvik Materials Technology, Strategy research, Sandviken, Sweden.
    Influence of Dynamic Strain Ageing and Long Term Ageing on Deformation and Fracture Behaviors of Alloy 6172016In: THERMEC 2016 / [ed] C. Sommitsch, M. Ionescu, B. Mishra, E. Kozeschnik and T. Chandra, Trans Tech Publications, 2016, Vol. 879, p. 306-311Conference paper (Refereed)
    Abstract [en]

    Influences of dynamic strain ageing and long term ageing on deformation, damage and fracture behaviors of Alloy 617 material have been studied. Dynamic strain ageing can occur in this alloy at temperature from 400 to 700°C, which leads to a strain hardening and also an increase in fracture strain due to plastic deformation caused by twinning. Long term ageing at 700°C for up to 20 000 hours can cause different precipitation such as γ ́, M6C (Mo-rich) and M23C6 (Cr-rich) carbides. These carbides are both inter-and intra-granular particles. The long term ageing reduces the fracture toughness of the material, but the alloy can still have rather high impact toughness and fracture toughness even with an ageing at 700°C for 20 000 hour. The mechanisms have been studied using electron backscatter detection and electron channeling contrast imaging. It shows that besides dislocation slip, twinning is another main deformation mechanism in these aged Alloy 617 materials. At the crack front, plenty of micro or nanotwins can be observed. The formation of these twins leads to a high ductility and toughness which is a new observation or a new concept for this type of material.

  • 30.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Mat Technology, Sweden.
    Forsman, T.
    Sandvik Mat Technology, Sweden.
    Gustavsson, F.
    Sandvik Mat Technology, Sweden.
    Wang, C.
    University of Paris Ouest Nanterre La Def, France.
    Formation of fine grained area in martensitic steel during very high cycle fatigue2015In: Fatigue & Fracture of Engineering Materials & Structures, ISSN 8756-758X, E-ISSN 1460-2695, Vol. 38, no 11, p. 1315-1323Article in journal (Refereed)
    Abstract [en]

    A fine grained area around a subsurface fatigue crack origin can usually be observed on fracture surface of a metallic material after very high cycle fatigue. This paper provides a fundamental study on the mechanisms to form this fine grained area using a martensitic stainless steel and advanced analysis instruments. The results show that the formation of a fine grained zone is a local behaviour. It is only a few micrometres in the transversal direction (cross section) and one micrometre in the longitudinal direction (crack propagation direction). High plastic deformation such as localized dislocation slip bands can be observed in this fine grained area. They interact with grain boundaries and cause the formation of damage by impingement cracking. The results indicate that occurrence of cyclic localized plastic deformation during very high cycle fatigue near the subsurface defect leads to the formation of fine grained area.

  • 31.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. R&D Center, Sandvik Materials Technology, Sandviken, Sweden.
    Forsman, Tomas
    R&D Center, Sandvik Materials Technology, Sandviken, Sweden.
    Gustavsson, Fredrik
    R&D Center, Sandvik Materials Technology, Sandviken, Sweden.
    Microscopic and Nanoscopic Study on Subsurface Damage and Fatigue Crack Initiation During Very High Cycle Fatigue2016In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 83, no 2, p. 288-292Article in journal (Refereed)
    Abstract [en]

    “Fish eye” is a typical phenomenon of fatigue crack initiation at a subsurface defect such as inclusion during very high cycle fatigue. The formation of a fine grained area and micro-debonding is believed to cause fatigue crack initiation. This paper provides a basic study on the formation of the fine grained area in a martensitic stainless steel during very high cycle fatigue using scanning electron microscopy, SEM, focused ion beam technique, FIB, electron backscatter diffraction, EBSD, and electron channeling contrast imaging, ECCI. The results show that the formation of a fine grained zone is a local behavior. The fine grained zone is very near the fatigue crack initiation origin. In the transversal direction (cross section), the depth of the fine grained zone is only few micrometers. In the longitudinal direction (crack propagation direction), the depth of the fine grain zone is about one micrometer. ECCI analysis shows that in the fine grained area with high retained strain, high plastic deformation can be found. Dislocation slip bands can be observed. They interact with grain boundaries and cause the formation of damage due to impingement cracking. The results indicate that occurrence of plastic deformation in metallic material during very high cycle fatigue is very localized, mainly near the front of the crack tip or a defect.

  • 32.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Materials Technology,Sandviken, Sweden .
    Hernblom, Johan
    Sandvik Materials Technology,Sandviken, Sweden .
    Peltola, Timo
    Sandvik Materials Technology,Sandviken, Sweden .
    Forsberg, Urban
    Sandvik Materials Technology,Sandviken, Sweden .
    Creep Behavior in A Newly Developed Heat Resistant Austenitic Stainless Steel2015In: Berg- und Huttenmännische Monatshefte (BHM), ISSN 0005-8912, E-ISSN 1613-7531, Vol. 160, no 9, p. 400-405Article in journal (Refereed)
    Abstract [en]

    UNS S31035 austenitic stainless steel grade is a newly developed advanced heat resistant material for use in coal fired boilers at metal temperatures up to 700 °C. This new grade that has recently got two AMSE code cases shows good resistance to steam oxidation and flue gas corrosion and high creep rupture strength. This paper will mainly focus on the characterization of long term structure stability and performances such as the creep behaviors at different temperatures for up to 86,000 h at high temperatures. The creep damage mechanisms were studied using electron transmission microscopy, electron backscatter diffraction, and electron channeling contrast image analysis. The results show that the creep strength is related to the intragranular nano particles that act as obstacles for dislocation movements. Plastic deformation and transgranular fracture is the main creep fracture mechanism in the creep test samples of UNS S31035. The material has good creep ductility by formation of twins during the creep test. This material has been installed and tested in several European power plants, and has shown good performance. The material is an excellent alternative for superheaters and reheaters in future high-efficient coal fired boilers with design material temperatures up to 700 °C, instead of more costly nickel based alloy. 

  • 33.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Hernblom, Johan
    R&D Centre, Sandvik Materials Technology, Sandviken.
    Peltola, Timo
    Global Product Management and Global Technical, Sandviken.
    Forsberg, Urban
    Global Product Management and Global Technical, Sandviken.
    Sanicro 25 - An Advanced High Strength Heat Resistant Austenitic Stainless Steel2016Conference paper (Refereed)
  • 34.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Kangas, Pasi
    R&D Centre, Sandvik Materials Technology, Sandviken, Sweden.
    Recent Developments of Advanced Austenitic and Duplex Stainless Steels for Applications in Oil & Gas Industry2014In: Proceedings of the 2014 Energy Materials Conference  (CD-ROM), Wiley-TMS , 2014, p. 703-709Conference paper (Refereed)
    Abstract [en]

    The demands for fuel and the development of the fuel exploitation processes have make it economically possible to produce oil-gas from deeper and more corrosive wells where the parameters such as high chloride, H2S or CO2 content, high temperature and pressure, erosion and bioactivities in seawater should be considered. In these applications, special grades of stainless steels with greater corrosion resistance at a broad range of temperatures and high strength have to be used to meet the requirements. This paper provides an overview on the development, properties and applications of these advanced materials for oil & gas industry. They include recently developed advanced super austenitic stainless steels with high Mo, Ni, Cr and N contents with a PRE number up to 52 and hyper duplex stainless steels.

  • 35.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Kivisäkk, Ulf
    Sandvik Materials Technology, R&D Centre, Sandviken, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hydrogen Induced Stress Cracking Behavior in Duplex Stainless Steels2013Conference paper (Other academic)
  • 36.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Kjellström, Patrik
    Strategy Research, Sandvik Materials Technology, Sandviken, Sweden.
    Boström, Magnus
    Strategy Research, Sandvik materials Technology, Sandviken, Sweden.
    Creep and Fracture Behaviors of an Advanced Heat Resistant Austenitic Stainless Steel for A-USC Power Plant2013Conference paper (Other academic)
  • 37.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Lillbacka, Robert
    FS Dynamics, Göteborg.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Micro Heterogeneous Fatigue Behavior of Duplex Stainless Steel During Cyclic Loading2012Conference paper (Other academic)
  • 38.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Liu, Ping
    Sandvik Materials Technology, Sandviken, Sweden.
    Zhou, Nian
    Sandvik Materials Technology, Sandviken, Sweden.
    Frodigh, Johan
    Sandvik Materials Technology, Sandviken, Sweden.
    Low and High Cycle Fatigue Behavior of Nickel-base Alloy att High Temperatures2013Conference paper (Refereed)
    Abstract [en]

    Low and high cycle fatigue behaviors of Alloy 690 have been investigated at temperatures up to 330 °C and number of cycles up to 2 × 109. Two interesting phenomena were observed. At high temperature, the alloy shows a secondary strain hardening in the cyclic stress-strain response. Formation of nano-twins and interactions between moving dislocations and stacking faults or interstitial atoms could contribute to this secondary strain hardening. For very high cycle fatigue, subsurface fatigue crack initiation at grain boundaries has been observed. EBSD investigation shows that strain accumulation is much localized. The fatigue damage is a localised plasticity exhaustion process.

  • 39.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Micro Deformation Behavior in Duplex Stainless Steels2015Conference paper (Other academic)
  • 40.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Fatigue Behaviors in Duplex Stainless Steel Studied Using In-Situ SEM-EBSD Method2014In: Procedia Materials Science, ISSN 2211-8128, Vol. 3, p. 1748-1753Article in journal (Refereed)
    Abstract [en]

    Austenite and ferrite in duplex stainless steels have different physical and mechanical properties. They can behave different during cyclic loading. To understand the fatigue behaviors of these two phases, an in-situ SEM/EBSD fatigue test has been performed. Flat specimens made from the specimens of pre-fatigue tested with three point bending were cyclically loaded in a scanning electron microscope via a compact test rig. By in situ/ex situ SEM/EBSD examination, slip activities and propagation of the fatigue cracks have been studied. Microstructures along the path of the fatigue crack were characterized. The different phase properties seem to lead to certain difference in the slip activity and formation of PSBs. Inhomogeneous slip activities and local strain concentrations were also found, which developed with increasing number of load cycles. Crack propagation behaviors in grain and cross the grain or phase boundaries have been discussed. Crack deflection occurs at the phase boundaries, but crack branching occurs mainly in the grains due to the dislocation slip. In-situ SEM/EBSD fatigue test confirms that crack propagation deflection and formation of crack branches can significantly reduce the crack propagation rate.

  • 41.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Micro Fatigue Crack Propagation Behavior in a Duplex Stainless Steel Studied Using In Situ SEM/EBSD Method2014In: 11TH INTERNATIONAL FATIGUE CONGRESS, PTS 1 AND 2, Trans Tech Publications Inc., 2014, Vol. 891-892, p. 313-318Conference paper (Refereed)
    Abstract [en]

    Fatigue crack propagation behaviors in a duplex stainless steel have been studied using an in-situ SEM/EBSD fatigue test and a conventional da/dN test. Crack propagation behaviors in grain, effect of Schmid factor, propagation cross the grain or phase boundaries have been discussed. Crack propagation occurs mainly in the grains with a high Schmid factor, but with very small Schmid factor. Crack deflection occurs mainly at the phase boundaries, but crack branching occurs mainly in the grains due to the dislocation slip. In-situ SEM/EBSD fatigue test confirms that crack propagation deflection can lead to a decrease in crack propagation rate. Formation of crack branches can significantly reduce the crack propagation rate, which can cause crack growth retardation in the main crack path in the worst case. The crack branches formed are usually not ideal. They can propagate almost transversely to the main crack direction with a mode II stress intensity factor, SIF, and a rate that is much higher than that of the main crack.

  • 42.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Kivisäkk, Ulf
    Sandvik Materials Technology, R&D Centre, Sandviken.
    Hydrogen Induced Stress Cracking in Heterogeneous Materials2012Conference paper (Other academic)
  • 43.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Sand, Tommy
    Sandvik Materials Technology, Sandviken, Sweden.
    Hernblom, Johan
    Sandvik Materials Technology, Sandviken, Sweden.
    Forsberg, Urban
    Sandvik Materials Technology, Sandviken, Sweden.
    Peltola, Timo
    Sandvik Materials Technology, Sandviken, Sweden.
    Development of Advance Heat Resistant materials for IGCC and AUSC Power Plants2014In: Proceedings of the 2014 Energy Materials Conference  (CD-ROM), Wiley-TMS , 2014, p. 227-234Conference paper (Refereed)
    Abstract [en]

    Integrated gasification combined cycle (IGCC) power plants and advanced ultra-supercritical (AUSC) thermal power plants are believed to be used as future power plants for high efficient and clean energy production. Increase in the efficiency of these plants is mainly attributed to the increase in temperature and pressure, and the consequent environments become much tougher. This will give a great challenge to the materials used in these plants. The new materials with even higher creep strength combined with better corrosion resistance need to be developed. This paper will provide an overview on the newly developed advanced heat resistant materials for these applications. It will mainly focus the following two types of materials. One is a newly developed advanced heat resistant austenitic stainless steels for AUSC boilers. The material has been tested in several boilers in Europe. Another is one type of composite tube material for convective syngas cooler in the coal gasification process, reverse composite tubes for the fire-tube boiler. A 15 years' application experience of this type of composite tube material will be discussed.

  • 44.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Stenvall, Peter
    Strategy Research, Sandvik Materials Technology, Sandviken, Sweden.
    Mechanisms for Cleavage Fracture in Duplex Stainless Steels2013Conference paper (Other academic)
  • 45.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Stenvall, Peter
    Study of Impact Toughness Behaviour of Duplex Stainless Steels Using Instrumental Testing Machine2015Conference paper (Refereed)
  • 46.
    Chai, Guocai
    et al.
    Sandvik Materials Technology, Sandviken, Sweden.
    Zhou, Nian
    Sandvik Materials Technology, Sandviken.
    Study of Crack Initiation or Damage in Very High Cycle Fatigue Using Ultrasonic Fatigue Test and Microstructure Analysis2013In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 53, no 8, p. 1406-1411Article in journal (Refereed)
    Abstract [en]

    Fatigue damage behaviors of four metal materials in the very high cycle fatigue (VHCF) regime have been studied using ultrasonic fatigue test and microstructure analysis. The results show that the fatigue crack initiation in VHCF regime could occur at subsurface non-defect fatigue crack origin (SNDFCO), where the accumulated cyclic strains or damage in the specimens were highly localized, especially in the materials with some softer phase, where the local maximum strain can be eight times higher than the average strain value in the specimen. This high strain localization can cause a local plasticity exhaustion that leads to a stress concentration and consequently fatigue crack initiation, and finally the formation of SNDFCO. For pure single phase austenitic material, strain localization can also occur due to dislocation accumulation at or near grain boundaries, which can become fatigue crack initiation origin in the VHCF regime. The results in this study show that fatigue damage and crack initiation mechanisms in the VHCF regime can be different in different metals due to the mechanisms for local plasticity exhaustion.

  • 47.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Zhou, Nian
    Sandvik Materials Technology, Sandviken.
    Ciurea, Sorina
    Sandvik Materials Technology, Sandviken.
    Andersson, Marcus
    Sandvik Materials Technology, Sandviken.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Local Plasticity Exhaustion in a Very High Cycle Fatigue Regime2012In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 66, no 10, p. 769-772Article in journal (Refereed)
    Abstract [en]

    Very high cycle fatigue behaviors of four metal materials with different microstructures have been studied focusing on their damage mechanisms. It was found that the cyclic plastic deformation in the materials was highly localized in the very high cycle regime or the elastic deformation regime. This high strain localization can cause local plasticity exhaustion, which leads to a stress concentration and consequently fatigue crack initation, and finally the formation of a subsurface non-defect fatigue crack origin.

  • 48. Gaddam, Raghuveer
    et al.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Stenvall, Peter
    peter.stenvall@sandvik.com.
    Impact Behaviour of Supler Duplex Stainless Steel Weldments at Sub-Zero Temperatures2015Conference paper (Refereed)
  • 49.
    Gärdsback, Magnus
    et al.
    Sandvik Materials Technology, Sandviken.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Hedström, David
    Sandvik Materials Technology, Sandviken.
    Persson, Katarina
    Sandvik Materials Technology, Sandviken.
    Influence of Strain Path on Work Hardening and Texture in an Austenitic Stainless Steel2014In: THERMEC 2013, Trans Tech Publications Inc., 2014, Vol. 783-786, p. 2567-2572Conference paper (Refereed)
    Abstract [en]

    The effect of strain path on work hardening and texture for a super austenitic stainless steel was investigated using both experiments and modeling. Compression deformation tests by stepwise changing loading direction in two and three dimensions were performed on cubic specimens at room temperature. The results were compared to uniaxial compression with equal accumulative strain, up to 20%, and uniaxial tension with equal final strain, up to 10% elongation of the longest side. The textures in all samples were analyzed using pole figures from EBSD analysis. Because of the high stacking fault energy of this super austenitic stainless steel, the texture was dominated by <110>-fiber texture in the compressive direction for the uniaxial compression, <111>- and <100>-fiber texture in the tensile direction for the uniaxial tensile test, and a combination of all these for the cube deformation. The density of the texture was much weaker for samples where the loading direction altered, if samples with equal accumulated strain were compared. The cube deformation was also modeled using a crystal plasticity model. The crystal plasticity model consists of a representative volume element (RVE) containing crystal grains with random orientations. The Taylor assumption was used for homogenization between the macro-and subscale. The material parameters in the crystal plasticity model were determined by calibration of its macroscopic response to experimental data. The simulated textures correspond rather well to the experimental results, but the work hardening should be completed to take into account kinematic hardening.

  • 50. Hareland, Mathias
    et al.
    Hoel, Anders
    Jonsson, Stefan
    Liang, David
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Sandvik Materials Technology, Sandviken, Sweden.
    Selection of Flapper Valve Steel for High Efficient Compressor2014Conference paper (Refereed)
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