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  • 401.
    Yuan, Kang
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    A Continuous β-NiAl Layer Forming at the Interface of a MCrAlY and CMSX-42016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1, p. 244-251Article in journal (Refereed)
    Abstract [en]

    A large test sample of single-crystal superalloy (CMSX-4) deposited with a MCrAlY coating of γ and β phases was subjected to a thermal-cycling fatigue (TCF) test at 1100 °C for about 300 cycles. Near the coating-substrate interface where an inner β-depletion zone often develops in the coating for other superalloy-MCrAlY systems, a continuous β-layer was formed instead for this particular system after the TCF test. The formation of the β-layer was related to the accumulation of Al at the interface. Simulations using an oxidation-diffusion model were carried out on this and a number of other superalloy-MCrAlY systems. It was derived that the formation of the β-layer at the interface was likely due to the high Al activity of CMSX-4 which resisted the inward diffusion of Al from the coating. The simulation results also indicated a positive effect provided by the formation of the β-layer on the coating’s oxidation resistance.

  • 402. Yuan, Kang
    et al.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Formation of a Continuous β-NiAl Layer Near the Interface in a γ+β MCrAIY2015In: / [ed] ASM International, 2015, p. 54-61Conference paper (Refereed)
  • 403.
    Yuan, Kang
    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.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Johansson, Lennart
    Siemens Industrial Turbomachinery AB, Finspång.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Wang, Yandong
    School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
    Analysis on Microstructural Evolution of PtAl Diffusion Coating on Ni-based Superalloy Influenced by Creep Process2012Conference paper (Other academic)
    Abstract [en]

    The microstructural evolution of PtAl diffusion coating on a nickel-base superalloy IN792 was studied to assess the influence of high temperature (850 °C and 950 °C) and static creep loading conditions. The chemical composition analysis by EDS reveals that local enrichment of Cr, W and Mo is responsible for the formation of σ, Cr-α and μ/R particles in the different characteristic zones in the PtAl coating. Being taken as an approach to describe the coating’s microstructure evolution, a so-called Effective Coating Thickness (ECT) is defined and was measured for different creep conditions. It is found that the value of ECT is controlled by the inward diffusion of Al and Pt, being demonstrated by the existence of a linear correlation between ECT and  diffusion coefficient of Al in substrate; t: diffusion time). Simulated ECT development of the PtAl diffusion coating agrees well with the experimental results at 850 °C and 950 °C.

  • 404.
    Yuan, Kang
    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.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Johansson, Lennart
    Siemens Industrial Turbomachinery AB, Finspång.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Wang, Yandong
    School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
    Creep Fracture Mechanism of Polycrystalline Ni-based Superalloy with Diffusion Coatings2013Conference paper (Other academic)
    Abstract [en]

    Diffusion coatings are widely used to increase oxidation and corrosion resistance of hot superalloy components for gas turbines. The aim of this study is to investigate the effect of coatings (NiAl and PtAl) on the creep fracture mechanism of samples with a substrate of IN792. The samples have been creep tested at two temperatures (850 °C and 950 °C) and different applied tensile stresses, until failure between 205 and 21000 hrs. The observation of cross-sections by SEM shows that the microstructural evolution in the coating is dependent on the diffusion of alloying elements in the sample. Furthermore the time and temperature induced growth of the coating is found to be controlled only by inward diffusion of Al. Grain-boundary cracking is the basic fracture mode in the substrate in all samples irrespective if the crack is initiated from coating or substrate. The analysis of microstructure shows that the diffusion coatings display two types of mechanical behavior - being easily plasticized or cracked - dependent on temperature and type of coating, and therefore can be considered as non-load carrying regions. After recalculating the creep stress to exclude the final effective coating thickness from the total sample thickness, the coated samples showed similar creep rupture behavior as the uncoated samples in the Larson-Miller diagram.

  • 405.
    Yuan, Kang
    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.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Johansson, Lennart
    Siemens Industrial Turbomachinery AB, Finspång.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Wang, Yandong
    School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
    Creep Fracture Mechanism of Polycrystalline Ni-based Superalloy with Diffusion Coatings2013Conference paper (Refereed)
  • 406.
    Yuan, Kang
    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.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of Precracked Diffusion Coating of Pt-Modified Aluminide on HCF Fracture Mechanism of IN 792 Nickel-Based Superalloy2012In: Applied Mechanics and Materials, ISSN 1660-9336, E-ISSN 1662-7482, Vol. 148-149, p. 24-29Article in journal (Refereed)
    Abstract [en]

    High-cycle-fatigue (HCF) fracture mechanism of nickel-based superalloy IN 792 coated with Pt-modified aluminide outward-diffusion coating is studied with focus on the influence of coating cracks. It is found that cracking of the diffusion coating prior to HCF tests has little influence on the fatigue limit of specimens with thin coating (50 μm) but lowers the fatigue limit of specimens with thick coating (70 μm). By fractographic analysis, three types of fractural modes are established according to their crack initiations: internal, external and mixed. While external fractural mode is related to the propagation of existing cracks in the coating, internal facture initiates often at Ti-Ta-W-rich carbides and/or topological-close-packed (TCP) phases and grainboundaries in the superalloy. Increasing the thickness of diffusion coating or the amplitude stress promotes the fractural mode transition from internal/mixed to external. The influence of precracking of coatings on the HCF fracture mechanism can be qualitatively explained by its influence on the stress intensity factor.

  • 407.
    Yuan, Kang
    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.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Wang, Yandong
    University of Science and Technology, Beijing, China.
    Simulation of oxidation-nitridation-induced microstructural degradation in a cracked Ni-based superalloy at high temperature2014In: MATEC Web of Conferences Vol. 14 (2014), EUROSUPERALLOYS 2014 – 2nd European Symposium on Superalloys and their Applications Giens, France, May 12–16, 2014, Les Ulis, France: E D P Sciences , 2014, Vol. 14, no 16004, p. 16004-Conference paper (Refereed)
    Abstract [en]

    In turbine engines, high temperature components made of superalloys may crack in a creep process during service. With the inward flux of the gases, e.g. oxygen and nitrogen, along those cracks, the microstructure of the superalloy substrate nearby the cracks may degrade by internal oxidation and nitridation. The aim of this study is to investigate and simulate the oxidation-nitridation-induced microstructural degradation in superalloys by taking a variant of Ni-based superalloy IN-792 as a sample. After the creep testing of the superalloy in air, the microstructures on the cross section of the superalloy were analysed in a scanning electron microscope, equipped with energy/wavelength dispersive systems. Internal oxidation and nitridation, presenting by Al/Ti oxides and nitrides, were observed under a porous and even cracked Cr-oxide scale which was formed on the superalloy surface or along the creep cracks connecting the superalloy surface. Meanwhile, the reinforcing γ′ precipitates were depleted. Such oxidation-nitridation-induced microstructural degradation was simulated by using an oxidation-diffusion model, focusing the diffusion of the alloying elements in metallic phases of the superalloy.

  • 408.
    Zhang, Pimin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Oxidation behaviour of MCrAlX coatings: effect of surface treatment and an Al-activity based life criterion2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    MCrAlY coatings (M=Ni and/or Co) have been widely used for the protection of superalloy components against oxidation and hot corrosion in the hot sections of gas turbines. The drive to improve engine combustion efficiency while reducing emissions by increasing the operation temperature brings a big challenge for coating design. As a result, the need for improvement of MCrAlY coatings for better oxidation resistance is essential.

    Formation of a stable, dense, continuous, and slow-growing α-Al2O3 layer, on the MCrAlY coating surface, is the key to oxidation protection, since the protective α-Al2O3 scale offers superior oxidation resistance due to its lower oxygen-diffusion rate as compared with other oxides. The ability of a MCrAlY coating to form and maintain such a protective scale depends on the coating composition and microstructure, and can be improved through optimization of deposition parameters, modification of coating surface conditions, and so on. Part of this thesis work focuses on studying the effect of post-deposition surface treatments on the oxidation behavior of MCrAlX coatings (X can be yttrium and/or other minor alloying elements). The aim is to gain fundamental understanding of alumina scale evolution during oxidation which is important for achieving improved oxidation resistance of MCrAlX coatings. Oxide scale formed on coatings at initial oxidation stage and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and weight gain. Results showed that both mechanically polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing growth of transient alumina, assisted by the high density of α-Al2O3 nuclei on surface treatment induced defects. The early development of a two-layer alumina scale, consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina, resulted in a higher oxide growth rate of the as-sprayed coating. The positive effect of the surface treatments on retarding oxide scale growth and suppressing formation of spinel was also observed in oxidation test up to 1000 hrs.

    As the oxidation proceeds to the close-to-end stage, a reliable criterion to estimate the capability of coating to form α-Al2O3 is of great importance to accurately evaluate coating lifetime, which is the aim of the other part of the thesis work. Survey of published results on a number of binary Ni-Al and ternary Ni-Cr-Al, Ni-Al-Si systems shows that the empirical Al-concentration based criterion is inadequate to properly predict the formation of a continuous α-Al2O3 scale. On the other hand, correlating the corresponding Al-activity data, calculated from measured chemical compositions using the Thermo-Calc software, to the experimental oxidation results has revealed a temperature dependent, critical Al-activity value for forming continuous α-Al2O3 scale. To validate the criterion, long-term oxidation tests were performed on five MCrAlX coatings with varying compositions and the implementation of the Al-activity based criterion on these coatings successfully predicted α-Al2O3 formation, showing a good agreement with experiment results.

    List of papers
    1. Long-term oxidation of MCrAlY coatings at 1000 degrees C and an Al-activity based coating life criterion
    Open this publication in new window or tab >>Long-term oxidation of MCrAlY coatings at 1000 degrees C and an Al-activity based coating life criterion
    Show others...
    2017 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, p. 12-21Article in journal (Refereed) Published
    Abstract [en]

    MCrAlY type (M = Ni and/or Co) coatings are widely used for the protection of components in the hot sections of gas turbines at high service temperatures by forming a continuous alpha-alumina. A reliable criterion to estimate the capability of coating to form alpha-alumina is of great importance to accurately evaluate coating lifetime. However, some coatings retain the ability to form a continuous alpha-alumina scale when the concentration of Al in coatings decreases to a critical level, therefore, the empirical Al-concentration based criterion is inadequate to properly predict the formation of a continuous alpha-alumina. Thus, a new life criterion, namely the critical Al-activity criterion, is proposed. In this work, the critical Al-activity to form a continuous a-alumina was validated by Al-activity calculation using Thermo-Calc software based on survey of research results of critical Al-concentration to form alpha-alumina on binary Ni-Al and ternary Ni-Cr-Al systems. Long-term oxidation tests were performed to support the criterion: three different MCrAlY coatings coated on IN-792 superalloy substrates were oxidized at 1000 degrees C for various periods of time up to 10,000 h. The microstructural evolution of MCrAlY coatings was investigated using Scanning Electron Microscope. The near-surface Al concentration and interdiffusion behaviour between substrate and coating were measured using Energy Dispersive X-ray Spectroscopy. The new critical Al-activity criterion has been successfully adopted in alpha-alumina formation prediction, showing a good agreement with experiment results. Therefore, it can be concluded that the extrapolation of new criterion from binary and ternary systems to multi-alloyed MCrAlY system is reasonable. Furthermore, the partial pressure of oxygen (P-O2) in atmosphere has been taken into consideration by combination with Al-activity to calculate the critical chemical reaction constant (K) of formation of a-alumina. The potential applicability of the methodology to predict MCrAlY life is also discussed.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE SA, 2017
    Keywords
    MCrAIY; Al-activity; alpha-Alumina; Life criterion; Long-term oxidation
    National Category
    Manufacturing, Surface and Joining Technology
    Identifiers
    urn:nbn:se:liu:diva-144267 (URN)10.1016/j.surfcoat.2017.09.086 (DOI)000418968100003 ()
    Conference
    44th International Conference on Metallurgical Coatings and Thin Films (ICMCTF)
    Note

    Funding Agencies|Siemens Industrial Turbomachinery AB (Finspang, Sweden); Swedish Energy Agency through KME consortium [KME-703]; research school of Agora Materials and AFM Strategic Faculty Grant SFO-MAT-LiU in Linkoping University [2009-00971]

    Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2019-11-04
    2. Isothermal oxidation behavior of HVAF-sprayed NiCoCrAlY coatings: Effect of surface treatment
    Open this publication in new window or tab >>Isothermal oxidation behavior of HVAF-sprayed NiCoCrAlY coatings: Effect of surface treatment
    Show others...
    2017 (English)In: Proceedings of International Thermal Sprayed Conference (ITSC), May 7-9,Germany, 456-461 (2017), 2017, p. 456-461Conference paper, Oral presentation only (Other academic)
    Abstract [en]

    NiCoCrAlY coatings are widely used as bond coats for ceramic thermal barrier coatings (TBCs) andoxidation and corrosion protective overlay coatings in industrial gas turbines. High temperature oxidation behaviour of NiCoCrAlYs has a great influence on the coating performance and lifetime of TBCs. A promising route to decrease the oxidation rate of such coatings is post-coating surface modification which can facilitate formation of a uniform alumina scale with a considerably slower growth rate compared to the as-sprayed coatings. In this work, the effect of surface treatment by means of shot peening and laser surface melting (LSM) on the oxidation resistance of high velocity air-fuel (HVAF) sprayed NiCoCrAlY coatings was studied. Isothermal oxidation was carried out at 1000⁰C for 1000h. Results showed that the rough surface of as-sprayed HVAF sprayed coatings was significantly changed after shot peening and LSM treatment, with a compact and smooth appearance. After the exposure, the oxide scales formed on surface-treated NiCoCrAlY coatings showed different morphology and growth rate compared to those formed on as-sprayed coating surface. The oxidation behaviour of surface treated HVAF-sprayed NiCoCrAlY coatings were revealed and discussed.

    Keywords
    Surface treatment, shot peening, Laser Surface Melting (LSM), High Velocity Air-Fuel (HVAF), NiCoCrAlY coating
    National Category
    Manufacturing, Surface and Joining Technology Ceramics
    Identifiers
    urn:nbn:se:liu:diva-145094 (URN)
    Conference
    International Thermal Spray Conference & Exposition, ITSC 2017, Düsseldorf, Germany, June 7-9, 2017
    Available from: 2017-12-28 Created: 2018-02-09 Last updated: 2018-02-09
  • 409.
    Zhang, Pimin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Performance of MCrAlX coatings: Oxidation, Hot corrosion and Interdiffusion2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    MCrAlY coatings (M=Ni and/or Co) are widely used for the protection of superalloy components against oxidation and hot corrosion in the hot sections of gas turbines. The drive for coating systems to bestow adequate oxidation and corrosion resistance upon the components becomes urgent as an inevitable result of the necessary improvement in engine combustion efficiency and service lifetime. Through the careful design of the composition, MCrAlY coating performance can be optimized to meet the needs under different service conditions and component materials, therefore, “MCrAlX”, with “X” stands for the minor alloying elements, is used to highlight the effect. In the present thesis, the performance of new MCrAlX coatings is investigated with respect to oxidation, hot corrosion and interactions between coating-superalloy substrates.

    Oxidation of MCrAlX coatings can be generally categorized into initial, steady and close-to-end stages. Coating performance can be affected by various factors at different stages, therefore, experiments were designed by targeting the oxidation stages. Investigation on the initial stage oxidation behavior of MCrAlY coatings with post-deposition surface treatments reveals the different growth mechanisms of alumina scales. Surface treatments significantly reduce the alumina growth rate by suppressing transient alumina development and aiding the early formation of α-Al2O3, which improves the long-term oxidation performance of the coating. Similarly, the modification of minor alloy elements in MCrAlX coatings also serves the purpose. The oxidation behavior of new MCrAlX coatings was investigated at the steady oxidation stage, followed by the microstructure observation, thermodynamic and kinetic simulations. As an alternative reactive element addition of Y, Ce shows a negative effect on the formation of columnar alumina scales of high strain tolerance. In comparison, Fe or Ru addition shows no influence on alumina growth, rather than strengthening the phase stability in the coating and reducing the interdiffusion between coating-substrate through different mechanisms. As the oxidation proceeds to the close-to-end stage, a reliable criterion to estimate the capability of coating to form α-Al2O3 is of great importance to accurately evaluate coating lifetime. A temperature-dependent critical Al-activity criterion was proposed to better predict the formation of a continuous α-Al2O3 scale based on correction of elemental activity using thermodynamic database to replace the empirical Al-concentration based criterion.

    Severe interdiffusion occurs between coating-substrate during high temperature oxidation, accelerating the degradation of the system. Interdiffusion behavior of diffusion couples of superalloys-MCrAlX coatings were examined. It is highlighted that the recrystallization of superficial layer of the substrate contributes to the secondary reaction zone formation and element interdiffusion controls subsequent zone thickening.

    Study on Type I hot corrosion behavior of new MCrAlX coatings shows that the addition of Fe has no influence on basic fluxing reactions before severe Al depletion from the coating occurs. Instead, it boosts the “effective” Al supply of coating by shifting the equilibrium concentration of Al in the γ phase to a low Al level. Besides, the pre-mature coating degradation at the coating-substrate interface was due to the fast growth of corrosion products from substrate induced large local volume expansions, resulting in early coating spallation.

    List of papers
    1. Long-term oxidation of MCrAlY coatings at 1000 degrees C and an Al-activity based coating life criterion
    Open this publication in new window or tab >>Long-term oxidation of MCrAlY coatings at 1000 degrees C and an Al-activity based coating life criterion
    Show others...
    2017 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, p. 12-21Article in journal (Refereed) Published
    Abstract [en]

    MCrAlY type (M = Ni and/or Co) coatings are widely used for the protection of components in the hot sections of gas turbines at high service temperatures by forming a continuous alpha-alumina. A reliable criterion to estimate the capability of coating to form alpha-alumina is of great importance to accurately evaluate coating lifetime. However, some coatings retain the ability to form a continuous alpha-alumina scale when the concentration of Al in coatings decreases to a critical level, therefore, the empirical Al-concentration based criterion is inadequate to properly predict the formation of a continuous alpha-alumina. Thus, a new life criterion, namely the critical Al-activity criterion, is proposed. In this work, the critical Al-activity to form a continuous a-alumina was validated by Al-activity calculation using Thermo-Calc software based on survey of research results of critical Al-concentration to form alpha-alumina on binary Ni-Al and ternary Ni-Cr-Al systems. Long-term oxidation tests were performed to support the criterion: three different MCrAlY coatings coated on IN-792 superalloy substrates were oxidized at 1000 degrees C for various periods of time up to 10,000 h. The microstructural evolution of MCrAlY coatings was investigated using Scanning Electron Microscope. The near-surface Al concentration and interdiffusion behaviour between substrate and coating were measured using Energy Dispersive X-ray Spectroscopy. The new critical Al-activity criterion has been successfully adopted in alpha-alumina formation prediction, showing a good agreement with experiment results. Therefore, it can be concluded that the extrapolation of new criterion from binary and ternary systems to multi-alloyed MCrAlY system is reasonable. Furthermore, the partial pressure of oxygen (P-O2) in atmosphere has been taken into consideration by combination with Al-activity to calculate the critical chemical reaction constant (K) of formation of a-alumina. The potential applicability of the methodology to predict MCrAlY life is also discussed.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE SA, 2017
    Keywords
    MCrAIY; Al-activity; alpha-Alumina; Life criterion; Long-term oxidation
    National Category
    Manufacturing, Surface and Joining Technology
    Identifiers
    urn:nbn:se:liu:diva-144267 (URN)10.1016/j.surfcoat.2017.09.086 (DOI)000418968100003 ()
    Conference
    44th International Conference on Metallurgical Coatings and Thin Films (ICMCTF)
    Note

    Funding Agencies|Siemens Industrial Turbomachinery AB (Finspang, Sweden); Swedish Energy Agency through KME consortium [KME-703]; research school of Agora Materials and AFM Strategic Faculty Grant SFO-MAT-LiU in Linkoping University [2009-00971]

    Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2019-11-04
    2. Investigation of Element Effect on High-Temperature Oxidation of HVOF NiCoCrAlX Coatings
    Open this publication in new window or tab >>Investigation of Element Effect on High-Temperature Oxidation of HVOF NiCoCrAlX Coatings
    2018 (English)In: Coatings, ISSN 2079-6412, Vol. 8, no 4, p. 129-145Article in journal (Refereed) Published
    Abstract [sv]

    MCrAlX (M: Ni or Co or both, X: minor elements) coatings have been used widely to protect hot components in gas turbines against oxidation and heat corrosion at high temperatures. Understanding the influence of the X-elements on oxidation behavior is important in the design of durable MCrAlX coatings. In this study, NiCoCrAlX coatings doped with Y + Ru and Ce, respectively, were deposited on an Inconel-792 substrate using high velocity oxygen fuel (HVOF). The samples were subjected to isothermal oxidation tests in laboratory air at 900, 1000, and 1100 °C and a cyclic oxidation test between 100 and 1100 °C with a 1-h dwell time at 1100 °C. It was observed that the coating with Ce showed a much higher oxidation rate than the coating with Y + Ru under both isothermal and cyclic oxidation tests. In addition, the Y + Ru-doped coating showed significantly lower β phase depletion due to interdiffusion between the coating and the substrate, resulting from the addition of Ru. Simulation results using a moving phase boundary model and an established oxidation-diffusion model showed that Ru stabilized β grains, which reduced β-depletion of the coating due to substrate interdiffusion. This paper, combining experiment and simulation results, presents a comprehensive study of the influence of Ce and Ru on oxidation behavior, including an investigation of the microstructure evolution in the coating surface and the coating-substrate interface influenced by oxidation time.

    Place, publisher, year, edition, pages
    M D P I AG, 2018
    Keywords
    MCrAlX coatings, Ruthenium, Cerium, Oxidation, Simulation
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-148278 (URN)10.3390/coatings8040129 (DOI)000435187300014 ()
    Funder
    Swedish Energy AgencyLinköpings universitet
    Note

    Funding agencies: Carl Tryggers Stifelsen [CTS16:207]; Swedish Research Council [VR-2014-3079]; Erling-Persson Family Foundation [2017-10-09]; Promobilia Foundation [F17603]

    Available from: 2018-06-05 Created: 2018-06-05 Last updated: 2019-11-04Bibliographically approved
    3. The iron effect on oxidation and interdiffusion behaviour in MCrAlX coated Ni-base superalloys
    Open this publication in new window or tab >>The iron effect on oxidation and interdiffusion behaviour in MCrAlX coated Ni-base superalloys
    2019 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 166, article id 107599Article in journal (Refereed) Published
    Abstract [en]

    Two MCrAlX powders with different Fe content were deposited on an IN792 superalloy using high velocity oxygen-fuel spraying (HVOF). The oxidation and interdiffusion behaviour of the coated specimens were investigated at 900, 1000 and 1100 degrees C for different exposure times. Experimental results showed that high Fe addition in the MCrAlX coating had no obvious effect on oxidation, however, a great impact on coating-substrate interdiffusion and coating degradation was observed. Although no influence on Al diffusivity in IN792, high Fe addition promotes the formation of a discontinuous sigma phase layer at the coating/substrate interface, which retards Al diffusion in the IN792 substrate at 900 degrees C. To investigate Fe influence on phase equilibrium, thermodynamic calculation was also performed. It was shown that high Fe addition in the MCrAlX coating increased the beta phase fraction and stabilized the beta phase by extending the beta + gamma phase region. Besides, high Fe addition in the MCrAlX coating modifies Cr diffusion, and alters local phase equilibrium at the coating/substrate interface. These two factors suppress inner-beta depletion of high Fe containing coating. Grain coarsening of the coating can be observed during oxidation, it was retarded by high Fe addition. (C) 2019 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

    Place, publisher, year, edition, pages
    ELSEVIER SCI LTD, 2019
    Keywords
    Coating; Iron addition; Interdiffusion; Thermodynamics; Microstructure
    National Category
    Manufacturing, Surface and Joining Technology
    Identifiers
    urn:nbn:se:liu:diva-154527 (URN)10.1016/j.matdes.2019.107599 (DOI)000458260700003 ()
    Note

    Funding Agencies|Siemens Industrial Turbomachinery AB (Finspang, Sweden); Swedish Energy Agency through KME consortium; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]

    Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-11-04
    4. Failure Mechanism of MCrAlY Coating at the Coating-Substrate Interface under Type I Hot Corrosion
    Open this publication in new window or tab >>Failure Mechanism of MCrAlY Coating at the Coating-Substrate Interface under Type I Hot Corrosion
    2019 (English)In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 70, no 9, p. 1593-1600Article in journal (Refereed) Published
    Abstract [en]

    MCrAlY coatings are widely used to provide protection of hot component in modern gas turbine engines against high‐temperature oxidation and hot corrosion. Coating‐substrate interface, where the substrate is only partially covered by the coatings, is vulnerable to the hot corrosion attack. The accelerated degradation at the coating‐substrate interface can cause fast spallation of the coating, leading to the early failure of the gas turbine components. In this paper, MCrAlY powder was deposited on IN792 disks by high‐velocity oxygen‐fuel spraying. The hot corrosion behavior of the coated sample was investigated using (0.8Na, 0.2K)2SO 4 salt deposition at 900°C in lab air. Results showed a minor attack in the coating center, however, an accelerated corrosion attack at the coating‐substrate interface. The fast growth of corrosion products from substrate caused large local volume expansions at the coating‐substrate interface, resulting in an early coating spallation.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2019
    Keywords
    Coating-subtrate interface, hot corrosion, IN792, MCrAlY coating
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-155790 (URN)10.1002/maco.201810720 (DOI)000483817500006 ()2-s2.0-85063385770 (Scopus ID)
    Note

    Funding agencies:  KME consortium-ELFORSK; Linkoping University [SFO-Mat-LiU 2009-00971]

    Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2019-11-04Bibliographically approved
    5. Effects of Surface Finish on the Initial Oxidation of HVAF-sprayed NiCoCrAlY Coatings
    Open this publication in new window or tab >>Effects of Surface Finish on the Initial Oxidation of HVAF-sprayed NiCoCrAlY Coatings
    Show others...
    2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Journal of Surface and Coatings Technology, ISSN 0257-8972, Vol. 364, p. 43-56Article in journal (Refereed) Published
    Abstract [en]

    Oxide scale formed on HVAF-sprayed NiCoCrAlY coatings and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and mass gain. The initial oxidationbehaviour of as-sprayed, polished and shot-peened coatings at 1000 °C is studied. Both polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing the growth of transient alumina, assisted by a high density of α-Al2O3 nuclei on surface treatment induced defects. Moreover, the fast development of a two-layer alumina scale consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina resulted in a higher oxide growth rate of the as-sprayed coating.

    Place, publisher, year, edition, pages
    Elsevier: Elsevier, 2019
    Keywords
    Oxidation, Transient ot alpha transformation, Surface treatment, Polishing, Shot-peening, Photo-stimulated liminescence spectroscopy
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-154936 (URN)10.1016/j.surfcoat.2019.02.068 (DOI)000463302800006 ()2-s2.0-85062231529 (Scopus ID)
    Note

    Funding agencies: Siemens Industrial Turbomachinery AB (Finspang, Sweden) [KME-703]; Swedish Energy Agency through KME consortium [KME-703]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00

    Available from: 2019-03-06 Created: 2019-03-06 Last updated: 2019-11-04Bibliographically approved
    6. The iron effect on hot corrosion behaviour of MCrAlX coating in the presence of NaCl at 900 °C
    Open this publication in new window or tab >>The iron effect on hot corrosion behaviour of MCrAlX coating in the presence of NaCl at 900 °C
    2020 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 815, article id 152381Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    Cyclic hot corrosion tests of two MCrAlX coatings with different Fe contents were carried out in a molten salt (75 wt% Na2SO4 + 25 wt% NaCl) environment at 900 °C under type I hot corrosion. The positive effect of high Fe addition which reduces the advancing of corrosion front in the coating was discussed. The experimental results showed that the main corrosion reaction is the basic fluxing of Al, while Fe is relatively inert. Combined with thermodynamic modelling, it was demonstrated that a high Fe addition in MCrAlX coatings shifts the equilibrium Al content of the γ phase towards a low level and also reduces the loss of Cr from coating to the substrate. Both effects contributed to a higher “effective” Al supply of the coating to resist basic fluxing and thereby enhance the coating resistance to hot corrosion by reducing the rate of advancing of the corrosion front.

    Keywords
    Iron effect, Type I hot corrosion, MCrAlX coating, Thermodynamic, Effective Al content
    National Category
    Manufacturing, Surface and Joining Technology
    Identifiers
    urn:nbn:se:liu:diva-161512 (URN)10.1016/j.jallcom.2019.152381 (DOI)
    Available from: 2019-11-04 Created: 2019-11-04 Last updated: 2019-11-04Bibliographically approved
    7. Hot gas corrosion and its influence on the thermal cycling performance of suspension plasma spray TBCs
    Open this publication in new window or tab >>Hot gas corrosion and its influence on the thermal cycling performance of suspension plasma spray TBCs
    Show others...
    2019 (English)In: Proceedings of ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition, New York, NY: American Society of Mechanical Engineers , 2019Conference paper, Published paper (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs) manufactured with suspension plasma spray (SPS) are promising candidates for use in gas turbines due to their high strain tolerance during thermal cyclic fatigue (TCF). However, corrosion often occurs alongside thermal fatigue and coating durability under these conditions is highly desirable. The current study focuses on understanding the corrosion behavior and its influence on the thermal cyclic fatigue life of SPS TBCs. Corrosion tests were conducted at 780 OC using a mixed-gas (1SO2-0.1CO-20CO2-N2(bal.) in vol. %) for 168h. They were later thermally cycled between 100-1100 ⁰C with a 1h hold time at 1100 ⁰C. Corrosion test results indicated that the damage predominantly started from the edges and a milder damage was observed at the center. Nickel sulfide was observed on top of the top coat and also in the columnar gaps of the top coat. Chromium oxides were observed inside the top coat columnar gaps but close to the bond coat/top coat interface. They were believed to reduce the strain tolerance of SPS TBCs to an extent and also amplify the thermal mismatch stresses during TCF tests. This, together with a fast growth of alumina during the TCF, resulted in a significant drop in the TCF life compared to the standard TCF tests.

    Place, publisher, year, edition, pages
    New York, NY: American Society of Mechanical Engineers, 2019
    National Category
    Manufacturing, Surface and Joining Technology
    Identifiers
    urn:nbn:se:liu:diva-161516 (URN)
    Conference
    ASME Turbo Expo: Turbomachinery Technical Conference and Exposition, Phoenix, Arizona, USA, June 17-21, 2019
    Available from: 2019-11-04 Created: 2019-11-04 Last updated: 2019-11-04Bibliographically approved
  • 410.
    Zhang, Pimin
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Siemens Ind Turbomachinery AB, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    The iron effect on oxidation and interdiffusion behaviour in MCrAlX coated Ni-base superalloys2019In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 166, article id 107599Article in journal (Refereed)
    Abstract [en]

    Two MCrAlX powders with different Fe content were deposited on an IN792 superalloy using high velocity oxygen-fuel spraying (HVOF). The oxidation and interdiffusion behaviour of the coated specimens were investigated at 900, 1000 and 1100 degrees C for different exposure times. Experimental results showed that high Fe addition in the MCrAlX coating had no obvious effect on oxidation, however, a great impact on coating-substrate interdiffusion and coating degradation was observed. Although no influence on Al diffusivity in IN792, high Fe addition promotes the formation of a discontinuous sigma phase layer at the coating/substrate interface, which retards Al diffusion in the IN792 substrate at 900 degrees C. To investigate Fe influence on phase equilibrium, thermodynamic calculation was also performed. It was shown that high Fe addition in the MCrAlX coating increased the beta phase fraction and stabilized the beta phase by extending the beta + gamma phase region. Besides, high Fe addition in the MCrAlX coating modifies Cr diffusion, and alters local phase equilibrium at the coating/substrate interface. These two factors suppress inner-beta depletion of high Fe containing coating. Grain coarsening of the coating can be observed during oxidation, it was retarded by high Fe addition. (C) 2019 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

  • 411.
    Zhang, Pimin
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    The iron effect on hot corrosion behaviour of MCrAlX coating in the presence of NaCl at 900 °C2020In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 815, article id 152381Article in journal (Refereed)
    Abstract [en]

    Cyclic hot corrosion tests of two MCrAlX coatings with different Fe contents were carried out in a molten salt (75 wt% Na2SO4 + 25 wt% NaCl) environment at 900 °C under type I hot corrosion. The positive effect of high Fe addition which reduces the advancing of corrosion front in the coating was discussed. The experimental results showed that the main corrosion reaction is the basic fluxing of Al, while Fe is relatively inert. Combined with thermodynamic modelling, it was demonstrated that a high Fe addition in MCrAlX coatings shifts the equilibrium Al content of the γ phase towards a low level and also reduces the loss of Cr from coating to the substrate. Both effects contributed to a higher “effective” Al supply of the coating to resist basic fluxing and thereby enhance the coating resistance to hot corrosion by reducing the rate of advancing of the corrosion front.

  • 412.
    Zhang, Pimin
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Failure Mechanism of MCrAlY Coating at the Coating-Substrate Interface under Type I Hot Corrosion2019In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 70, no 9, p. 1593-1600Article in journal (Refereed)
    Abstract [en]

    MCrAlY coatings are widely used to provide protection of hot component in modern gas turbine engines against high‐temperature oxidation and hot corrosion. Coating‐substrate interface, where the substrate is only partially covered by the coatings, is vulnerable to the hot corrosion attack. The accelerated degradation at the coating‐substrate interface can cause fast spallation of the coating, leading to the early failure of the gas turbine components. In this paper, MCrAlY powder was deposited on IN792 disks by high‐velocity oxygen‐fuel spraying. The hot corrosion behavior of the coated sample was investigated using (0.8Na, 0.2K)2SO 4 salt deposition at 900°C in lab air. Results showed a minor attack in the coating center, however, an accelerated corrosion attack at the coating‐substrate interface. The fast growth of corrosion products from substrate caused large local volume expansions at the coating‐substrate interface, resulting in an early coating spallation.

  • 413.
    Zhang, Pimin
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Hot Corrosion Behavior of HVOF CoNiCrAlY(Hf) Coating on Ni-based Superalloys2017Conference paper (Refereed)
  • 414.
    Zhang, Pimin
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Investigation of Element Effect on High-Temperature Oxidation of HVOF NiCoCrAlX Coatings2018In: Coatings, ISSN 2079-6412, Vol. 8, no 4, p. 129-145Article in journal (Refereed)
    Abstract [sv]

    MCrAlX (M: Ni or Co or both, X: minor elements) coatings have been used widely to protect hot components in gas turbines against oxidation and heat corrosion at high temperatures. Understanding the influence of the X-elements on oxidation behavior is important in the design of durable MCrAlX coatings. In this study, NiCoCrAlX coatings doped with Y + Ru and Ce, respectively, were deposited on an Inconel-792 substrate using high velocity oxygen fuel (HVOF). The samples were subjected to isothermal oxidation tests in laboratory air at 900, 1000, and 1100 °C and a cyclic oxidation test between 100 and 1100 °C with a 1-h dwell time at 1100 °C. It was observed that the coating with Ce showed a much higher oxidation rate than the coating with Y + Ru under both isothermal and cyclic oxidation tests. In addition, the Y + Ru-doped coating showed significantly lower β phase depletion due to interdiffusion between the coating and the substrate, resulting from the addition of Ru. Simulation results using a moving phase boundary model and an established oxidation-diffusion model showed that Ru stabilized β grains, which reduced β-depletion of the coating due to substrate interdiffusion. This paper, combining experiment and simulation results, presents a comprehensive study of the influence of Ce and Ru on oxidation behavior, including an investigation of the microstructure evolution in the coating surface and the coating-substrate interface influenced by oxidation time.

  • 415.
    Zhang, Pimin
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Sadeghimeresht, Esmaeil
    Dept of Engineering Science, University West, Trollhättan, Sweden.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicoclaie
    Dept of Engineering Science, University West, Trollhättan, Sweden.
    Joshi, Shrikant
    Dept of Engineering Science, University West, Trollhättan, Sweden.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Effects of Surface Finish on the Initial Oxidation of HVAF-sprayed NiCoCrAlY Coatings2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Journal of Surface and Coatings Technology, ISSN 0257-8972, Vol. 364, p. 43-56Article in journal (Refereed)
    Abstract [en]

    Oxide scale formed on HVAF-sprayed NiCoCrAlY coatings and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and mass gain. The initial oxidationbehaviour of as-sprayed, polished and shot-peened coatings at 1000 °C is studied. Both polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing the growth of transient alumina, assisted by a high density of α-Al2O3 nuclei on surface treatment induced defects. Moreover, the fast development of a two-layer alumina scale consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina resulted in a higher oxide growth rate of the as-sprayed coating.

  • 416.
    Zhang, Pimin
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Sadeghimeresht, Esmaeil
    Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicolaie
    Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Joshi, Shrikant
    Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Isothermal oxidation behavior of HVAF-sprayed NiCoCrAlY coatings: Effect of surface treatment2017In: Proceedings of International Thermal Sprayed Conference (ITSC), May 7-9,Germany, 456-461 (2017), 2017, p. 456-461Conference paper (Other academic)
    Abstract [en]

    NiCoCrAlY coatings are widely used as bond coats for ceramic thermal barrier coatings (TBCs) andoxidation and corrosion protective overlay coatings in industrial gas turbines. High temperature oxidation behaviour of NiCoCrAlYs has a great influence on the coating performance and lifetime of TBCs. A promising route to decrease the oxidation rate of such coatings is post-coating surface modification which can facilitate formation of a uniform alumina scale with a considerably slower growth rate compared to the as-sprayed coatings. In this work, the effect of surface treatment by means of shot peening and laser surface melting (LSM) on the oxidation resistance of high velocity air-fuel (HVAF) sprayed NiCoCrAlY coatings was studied. Isothermal oxidation was carried out at 1000⁰C for 1000h. Results showed that the rough surface of as-sprayed HVAF sprayed coatings was significantly changed after shot peening and LSM treatment, with a compact and smooth appearance. After the exposure, the oxide scales formed on surface-treated NiCoCrAlY coatings showed different morphology and growth rate compared to those formed on as-sprayed coating surface. The oxidation behaviour of surface treated HVAF-sprayed NiCoCrAlY coatings were revealed and discussed.

  • 417.
    Zhang, Pimin
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Yuan, Kang
    Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Siemens Ind Turbomachinery AB, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Long-term oxidation of MCrAlY coatings at 1000 degrees C and an Al-activity based coating life criterion2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, p. 12-21Article in journal (Refereed)
    Abstract [en]

    MCrAlY type (M = Ni and/or Co) coatings are widely used for the protection of components in the hot sections of gas turbines at high service temperatures by forming a continuous alpha-alumina. A reliable criterion to estimate the capability of coating to form alpha-alumina is of great importance to accurately evaluate coating lifetime. However, some coatings retain the ability to form a continuous alpha-alumina scale when the concentration of Al in coatings decreases to a critical level, therefore, the empirical Al-concentration based criterion is inadequate to properly predict the formation of a continuous alpha-alumina. Thus, a new life criterion, namely the critical Al-activity criterion, is proposed. In this work, the critical Al-activity to form a continuous a-alumina was validated by Al-activity calculation using Thermo-Calc software based on survey of research results of critical Al-concentration to form alpha-alumina on binary Ni-Al and ternary Ni-Cr-Al systems. Long-term oxidation tests were performed to support the criterion: three different MCrAlY coatings coated on IN-792 superalloy substrates were oxidized at 1000 degrees C for various periods of time up to 10,000 h. The microstructural evolution of MCrAlY coatings was investigated using Scanning Electron Microscope. The near-surface Al concentration and interdiffusion behaviour between substrate and coating were measured using Energy Dispersive X-ray Spectroscopy. The new critical Al-activity criterion has been successfully adopted in alpha-alumina formation prediction, showing a good agreement with experiment results. Therefore, it can be concluded that the extrapolation of new criterion from binary and ternary systems to multi-alloyed MCrAlY system is reasonable. Furthermore, the partial pressure of oxygen (P-O2) in atmosphere has been taken into consideration by combination with Al-activity to calculate the critical chemical reaction constant (K) of formation of a-alumina. The potential applicability of the methodology to predict MCrAlY life is also discussed.

  • 418.
    Zhou, J M
    et al.
    Division of Production and Materials Engineering, Lund university.
    Bushlya, V
    Division of Production and Materials Engineering, Lund university.
    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.
    Avdovic, P
    Siemens Industrial Turbomachinery, Finspång.
    Stahl, J-E
    Division of Production and Materials Engineering, Lund university.
    Effect of Tool Wear on Subsurface Deformation of Nickel-based Superalloy2011In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 19, p. 407-413Article in journal (Refereed)
    Abstract [en]

    Increased demand of energy efficiency for the components used in aerospace and energy industries requires high efficiency and low cost in the production of component made of nickel-based superalloy, such as aged Inconel 718. With use of whisker reinforced ceramic cutting tool in finishing machining process, higher cutting speed and higher production efficiency can be reached accordingly. However, surface integrity of the part produced by this process still needs to be studied due to the high demand of surface quality. The paper analyses the effects of tool wear on subsurface deformation of nickel-based super-alloy in finishing turning. The objective is to understand the nature of subsurface deformation under the influence of tool wear for prediction of the surface integrity in machined components based upon the machining conditions and material behaviours that give rise to them. Machined samples were studied under a Backscattered electron microscope to distinguish the subsurface features produced by the machining. The electron back scatter diffraction (EBSD) was also used to quantify the depth of deformation zones in the subsurface after the machining.

  • 419.
    Zhou, J M
    et al.
    Division of Production and Materials Engineering, Lund university.
    Bushlya, V
    Division of Production and Materials Engineering, Lund university.
    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.
    Avdovic, P
    Siemens Industrial Turbomachinery, Finspång.
    Stahl, J-E
    Division of Production and Materials Engineering, Lund university.
    On Process Induced Subsurface Deformation of Aged Inconel 718 in Relation to Different Cutting Conditions2011Conference paper (Refereed)
  • 420.
    Zhou, J M
    et al.
    Division of Production and Materials Engineering, Lund university.
    Bushlya, V
    Division of Production and Materials Engineering, Lund university.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Stahl, J-E
    Division of Production and Materials Engineering, Lund university.
    Identification of Subsurface Deformation in Machining of Inconel 7182011In: Applied Mechanics and Materials, ISSN 1660-9336, Vol. 117-119, p. 1681-1688Article in journal (Refereed)
    Abstract [en]

    There is considerable industrial significance to understand the nature of subsurface deformation under the machined surface for correct prediction of surface properties in machined components based upon the machined conditions and material behaviors that give rise to them. In this study, high speed machining of Inconel 718 was carried with whisker reinforced ceramic cutting tool under different conditions of tool wear, coolant state and cutting parameters. The objective of the present investigation was to determine the effect of both cutting parameters and tool wear on the plastic deformation in the subsurface region of Inconel 718 after the finishing machining with above process conditions. The surface and subsurface region of machined specimens were examined using a high resolution scan electron microscope (HRSEM) and EBSD technique, microhardness measurements were also conducted on the test samples, accordingly plastic strain analysis were carried out.

  • 421.
    Zhou, Jinming
    et al.
    Division of Production and Materials Engineering, Lund university.
    Bushlya, Volodymyr
    Division of Production and Materials Engineering, Lund university.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chen, Zhe
    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.
    Stahl, Jan-Erik
    Division of Production and Materials Engineering, Lund university.
    Analysis of Subsurface Microstructure and Residual Stresses in Machined Inconel 718 with PCBN and Al2O3-SiCw Tools2014In: 2ND CIRP CONFERENCE ON SURFACE INTEGRITY (CSI), Elsevier, 2014, Vol. 13, p. 150-155Conference paper (Refereed)
    Abstract [en]

    Subsurface microstructural alterations and residual stresses caused by machining significantly affect component lifetime and performance by influencing fatigue, creep, and stress corrosion cracking resistance. Assessing the surface quality of a machined part by characterizing subsurface microstructural alterations and residual stresses is essential for ensuring part performance and lifetime in aero-engines and power generators. This comparative study characterizes and analyzes subsurface microstructural alterations and residual stresses in Inconel 718 subjected to high-speed machining with PCBN and whisker-reinforced ceramic cutting tools. Effects of cutting tool materials and microgeometry on subsurface deformation, microstructural alterations, and residual stresses were investigated. Surface and subsurface regions of machined specimens were investigated using X-ray diffraction, electron channeling contrast imaging, and electron back-scatter diffraction to characterize microstructural alterations and measure deformation intensity and depth.

  • 422. Zhou, Jinming
    et al.
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Siemens Industrial Turbomachinery AB, Finspång.
    Persson, Henrik
    Div of Production and Materials Engineering, Lunds University.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    M'Saoubi, Rachid
    Seco Tools AB, Fagersta.
    Gustafsson, David
    Siemens Industrial Turbomachinery AB, Finspång.
    Comparative Assessment of the Surface Integrity of AD730 and IN718 Superalloys in High-Speed Turning with a CBN Tool2019In: Journal of Manufacturing and Materials Processing, ISSN 2504-4494, Vol. 3, no 3, article id 73Article in journal (Refereed)
    Abstract [en]

    Nickel-based superalloys are typical materials used in components of aeroengines and gas turbine machinery. The strength properties of these alloys at high temperatures are crucial not only to the performance (e.g., power generation efficiency, energy consumption, and greenhouse gas emissions) of aeroengines and industrial gas turbines, but also to machinability during component manufacturing. This study comparatively evaluated the surface integrity of two superalloys, AD730® and Inconel 718 (IN718), during high-speed finishing turning using cubic boron nitride (CBN) tools. IN718 is a conventional superalloy used for the hot section components of aeroengines and industrial gas turbines, while AD730® is a novel superalloy with enhanced high-temperature mechanical properties and good potential as a next-generation superalloy for these components. High-speed turning tests of two superalloys were conducted using a CBN cutting tool and jet stream cooling. The achieved surface integrity of the AD730® and IN718 superalloys was characterized and analyzed to assess the comparability of these alloys. 

  • 423. Zhou, Jinming
    et al.
    Persson, H
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    M'Saoubi, R
    Gustafsson, David
    Bushlya, Volodymyr
    Akujärvi, V
    Stahl, JE
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Surface Characterization of AD730™ Part Produced in High Speed Turning with CBN Tool2018In: Procedia CIRP 71 (2018) / [ed] Elsevier, 2018, Vol. 71, p. 215-220Conference paper (Refereed)
  • 424.
    Zhou, Nian
    et al.
    Dept of Materials Science, Dalarna University, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Pettersson, Rachel
    Jernkontoret, Stockholm.
    Surface Integrity of 2304 Duplex Stainless Steel After Different Grinding Operations2016In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, no 229, p. 294-304Article in journal (Refereed)
    Abstract [en]

    Surface integrity has significant effect on service performance of a component. In this study, the evolution of the surface and sub-surface changes induced by grinding duplex stainless steel (DSS) 2304 was studied with regard to the residual stress, the microstructure, surface roughness and surface defects. The results provide insights into the effect of abrasive grit size, grinding force and lubrication on the surface integrity. The abrasive grit size was found to have the largest influence. Surface defects, a highly deformed surface layer and the generation of tensile residual stresses along the grinding direction have been found to be the main types of damage induced by the grinding operation. Residual stresses induced by mechanical effects dominate over thermal effects in this study. The results obtained can be used to understand the contribution of surface condition and residual stress on failure of duplex stainless steels in service by fatigue or stress corrosion cracking.

  • 425.
    Zhou, Nian
    et al.
    Dept of Materials Science, Dalarna University, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Pettersson, Rachel
    KTH och Jernkontoret, Stockholm.
    Schönning, Mikael
    Corrosion Dept, Avesta Research Centre, Outokumpu Stainless AB, Avesta.
    Residual Stress in Stainless Steels after Surface Grinding and its Effect on Chloride Induced SCC2017In: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2017), Materials Research Forum , 2017, Vol. 2, p. 289-294Conference paper (Refereed)
    Abstract [en]

    The induced residual stresses in stainless steels as a consequence of surface grinding as well as their influence on the chloride induced stress corrosion cracking (SCC) susceptibility have been investigated. Three types of materials were studied: 304L austenitic stainless steel, 509 ferritic stainless steel and 2304 duplex stainless steel. Surface grinding using 60# and 180# grit size abrasives was performed for each material. Residual stress depth profiles were measured using X-ray diffraction. The susceptibility to stress corrosion cracking was evaluated in boiling MgCl2 according to ASTM G36. Specimens were exposed without applying any external loading to evaluate the risk for SCC caused solely by residual stresses. Induced residual stresses and corrosion behavior were compared between the austenitic, ferritic and duplex stainless steels to elucidate the role of the duplex structure. For all materials, the grinding operation generated tensile residual stresses in the surface along the grinding direction but compressive residual stresses perpendicular to the grinding direction. In the subsurface region, compressive stresses in both directions were present. Microcracks initiated due to high grinding-induced tensile residual stresses in the surface layer were observed in austenitic 304L and duplex 2304, but not in the ferritic 4509. The surface residual stresses decreased significantly after exposure for all specimens.

  • 426.
    Zhou, Nian
    et al.
    Dept of Materials Science, Dalarna University, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Schönning, Mikael
    Corrosion Dept, Avesta Research Centre, Outokumpu Stainless AB, Avesta.
    Pettersson, Rachel
    KTH och Jernkontoret, Stockholm.
    SCC of 2304 Duplex Stainless Steel - Microstructure, Residual Stress and Surface Grinding Effects2017In: Materials, ISSN 1996-1944, Vol. 10, no 221Article in journal (Refereed)
    Abstract [en]

    The influence of surface grinding and microstructure on chloride induced stress corrosion cracking (SCC) behavior of 2304 duplex stainless steel has been investigated. Grinding operations were performed both parallel and perpendicular to the rolling direction of the material. SCC tests were conducted in boiling magnesium chloride according to ASTM G36; specimens were exposed both without external loading and with varied levels of four-point bend loading. Residual stresses were measured on selected specimens before and after exposure using the X-ray diffraction technique. In addition, in-situ surface stress measurements subjected to four-point bend loading were performed to evaluate the deviation between the actual applied loading and the calculated values according to ASTM G39. Micro-cracks, initiated by grinding induced surface tensile residual stresses, were observed for all the ground specimens but not on the as-delivered surfaces. Loading transverse to the rolling direction of the material increased the susceptibility to chloride induced SCC. Grinding induced tensile residual stresses and micro-notches in the as-ground surface topography were also detrimental.

  • 427.
    Zhou, Nian
    et al.
    Dept of Materials Science, Dalarna University, Sweden.
    Pettersson, Rachel
    KTH och Jernkontoret, Stockholm.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Schönning, Mikael
    Corrosion Dept, Avesta Research Centre, Outokumpu Stainless AB, Avesta.
    Effect of Surface Grinding on Chloride Induced SCC of 304L2016In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 658, p. 50-59Article in journal (Refereed)
    Abstract [en]

    The effect of surface grinding on the stress corrosion cracking (SCC) behavior of 304L austenitic stainless steel in boiling magnesium chloride has been investigated. SCC tests were conducted both without external loading and with varied levels of four-point bend loading for as-delivered material and for specimens which had been ground parallel or perpendicular to the loading direction. Residual stresses due to the grinding operation were measured using the X-ray diffraction technique. In addition, surface stress measurements under applied load were performed before exposure to evaluate the deviation between actual applied loading and calculated values according to ASTM G39. Micro-cracks initiated by a high level of tensile residual stress in the surface layer were observed for all the ground specimens but not those in the as-delivered condition. Grinding along the loading direction increased the susceptibility to chloride induced SCC; while grinding perpendicular to the loading direction improved SCC resistance. Surface tensile residual stresses were largely relieved after the initiation of cracks.

  • 428.
    Zhou, Nian
    et al.
    Department of Material Science, Dalarna University, Falun, Sweden; KTH, Stockholm, Sweden.
    Pettersson, Rachel
    Jernkontoret, Stockholm; KTH, Stockholm, Sweden.
    Schönning, Mikael
    Corrosion Department, Avesta Research Center, Outokumpu Stainless AB, Avesta, Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Influence of Surface Grinding on Corrosion Behaviour of Ferritic Stainless Steels in Boiling Magnesium Chloride Solution2018In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 69, no 11, p. 1560-1571Article in journal (Refereed)
    Abstract [en]

    The influence of grinding operations on surface properties and corrosion behavior of a ferritic stainless steel (FSS), EN 1.4509, has been investigated and limited comparisons also made to the grade EN 1.4622. Surface grinding was performed along the rolling direction of the material. Corrosion tests were conducted in boiling magnesium chloride solution according to ASTM G36; specimens were exposed both without external loading and under four‐point bend loading. The surface topography and cross‐section microstructure before and after exposure were investigated, and residual stresses were measured on selected specimens before and after corrosion tests using X‐ray diffraction. In addition, in situ surface stress measurements were performed to evaluate the actual surface stresses of specimens subject to four‐point bend loading according to ASTM G39. Micro‐pits showing branched morphology initiated from the highly deformed ground surface layer which contained fragmented grains, were observed for all the ground specimens but not those in the as‐delivered condition. Grain boundaries under the surface layer appeared to hinder the corrosion process. No macro‐cracking was found on any specimen after exposure even at high calculated applied loads.

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