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  • 1.
    Baysal, Mustafa
    et al.
    Sabanci Univ, Turkey.
    Bilge, Kaan
    Sabanci Univ, Turkey; Imperial Coll London, England.
    Yildizhan, Melike
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Sabanci Univ, Turkey.
    Yorulmaz, Yelda
    Sabanci Univ, Turkey.
    Oncel, Cinar
    Mugla Sitki Kocaman Univ, Turkey.
    Papila, Melih
    Sabanci Univ, Turkey.
    Yurum, Yuda
    Sabanci Univ, Turkey.
    Catalytic synthesis of boron nitride nanotubes at low temperatures2018Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, nr 10, s. 4658-4662Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    KFeO2 is demonstrated to be an efficient catalyst for the formation of boron nitride nanotubes (BNNT) by thermal chemical vapor deposition (TCVD). This alkali-based catalyst enables the formation of crystalline, multi-walled BNNTs with high aspect ratio at temperatures as low as 750 degrees C, significantly lower than those typically required for the product formation by TCVD.

  • 2.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technol, Sandviken, Sweden.
    Kangas, Pasi
    Sandvik Mat Technol, Sandviken, Sweden.
    Super and hyper duplex stainless steels: structures, properties and applications2016Ingår i: 21ST EUROPEAN CONFERENCE ON FRACTURE, (ECF21), ELSEVIER SCIENCE BV , 2016, Vol. 2, s. 1755-1762Konferensbidrag (Refereegranskat)
    Abstract [en]

    In oil-gas industry, the exploration and development are now targeted to the deep reservoirs with high pressures, high temperatures and extreme corrosive environments. This requires that the materials used should have a good combination of extra high strength and excellent corrosion resistance. In order to meet these challenges, hyper duplex stainless steels have recently been developed. These materials have nitrogen contents up to about 0.5% and PRE-values close to 50, and show both highest corrosion pitting resistance and highest strength among the existing duplex stainless steels. The purpose of this paper is to provide an overview on hyper duplex stainless steels. It will mainly focus on the material development, microstructures, corrosion properties such as critical pitting corrosion temperature and crevice corrosion resistance, heterogeneous deformation behaviour of duplex stainless steel, and mechanical properties such as tensile properties and fatigue properties. These properties and the ratios of strength/weight will then be compared with those of other type of duplex stainless steels. The potential applications for hyper duplex stainless steels are also discussed. Copyright (C) 2016 The Authors. Published by Elsevier B.V.

  • 3. Chen, Jiaxin
    et al.
    Obitz, C
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska fakulteten.
    Forssgren, B
    CORROSION KINETICS OF NICKEL-BASE ALLOYS WITH HIGH CHROMIUM CONTENTS UNDER SIMULATED BWR NORMAL WATER CHEMISTRY CONDITIONS AND HIGH FLOW VELOCITY2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    In light water reactors corrosion-induced material degradation is a critical issue not only for material integrity but also for plant radiation field build-up. In BWRs nickel-base alloys, such as Alloy 600, Alloy 82 and Alloy 182, are applied in various parts of reactor components including welds. However, their corrosion mechanisms are not very well understood. Although the complex compositions of different nickel-base alloys generally prohibit us to single out some specific alloy constituent having a major impact on alloy corrosion rate, a higher chromium content is often thought to be beneficial to forming a more protective oxide film against corrosion attack. In this paper we report a corrosion kinetics study on high chromium nickel-base alloy welding consumables, Alloy 52M and Alloy 152, under simulated BWR normal water chemistry conditions and high flow velocity for up to nine weeks exposure. The corrosion rates are derived from measurements of weight losses of test coupons, oxide thicknesses with infrared ellipsometry, and microstructures of oxide films with electron microscopy. The obtained corrosion rates are then compared to that for Alloy 182, Alloy 82 and Alloy 600. The results show that the corrosion rate for Alloy 52M is similar to those for Alloy 182, whereas the rate for Alloy 152 is reduced to less than half. These observations indicate that the corrosion kinetics for nickel-base alloys is complex and alloy chromium content alone is not a dominant factor in influencing alloy corrosion rate.

  • 4.
    Chipatecua Godoy, Yuri
    et al.
    CINVESTAV, Mexico.
    Tengstrand, Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Olaya Florez, Jairo
    Univ Nacl Colombia, Colombia.
    Petrov, Ivan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Bustos, Erika
    CIDETEQ, Mexico.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Herrera-Gomez, Alberto
    CINVESTAV, Mexico.
    Greene, Joseph E
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci and Technol, Taiwan.
    Greczynski, Grzegorz
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Corrosion Resistant TiTaN and TiTaAlN Thin Films Grown by Hybrid HiPIMS/DCMS Using Synchronized Pulsed Substrate Bias with No External Substrate Heating2019Ingår i: Coatings, ISSN 2079-6412, COATINGS, Vol. 9, nr 12, artikel-id 841Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ti0.92Ta0.08N and Ti0.41Al0.51Ta0.08N thin films grown on stainless-steel substrates, with no external heating, by hybrid high-power impulse and dc magnetron sputtering (HiPIMS/DCMS), were investigated for corrosion resistance. The Ta target was operated in HiPIMS mode to supply pulsed Ta-ion fluxes, while two Ti (or Ti and Al) targets were operated in DCSM mode in order to provide a high deposition rate. Corrosion resistance was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy employing a 3.5% NaCl solution at room temperature. The 300-nm-thick transition-metal nitride coatings exhibited good corrosion resistance due to film densification resulting from pulsed heavy Ta-ion irradiation during film growth. Corrosion protective efficiencies were above 99.8% for both Ti0.41Al0.51Ta0.08N and Ti0.92Ta0.08N, and pore resistance was apparently four orders of magnitude higher than for bare 304 stainless-steel substrates.

  • 5.
    Eriksson, Robert
    et al.
    Siemens AG, Energy Sector, Berlin, Germany.
    Yuan, Kang
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Tekniska fakulteten.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Corrosion of NiCoCrAIY Coatings and TBC Systems Subjected to Water Vapor and Sodium Sulfate2015Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, nr 6, s. 953-964Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermal barrier coating (TBC) systems are commonly used in gas turbines for protection against high-temperature degradation. Penetration of the ceramic top coat by corrosive species may cause corrosion damage on the underlying NiCoCrAlY bond coat and cause failure of the TBC system. In the current study, four oxidation/corrosion conditions were tried: (i) lab air, (ii) water vapor, (iii) sodium sulfate deposited on the specimens, and (iv) water vapor + sodium sulfate. The test was done at 750 °C in a cyclic test rig with 48 h cycles. The corrosion damage was studied on NiCoCrAlY-coated specimens, thin APS TBC specimens, and thick APS TBC specimens. Water vapor was found to have very minor influence on the oxidation, while sodium sulfate increased the TGO thickness both for NiCoCrAlY specimens and TBC-coated specimens; the influence of the TBC thickness was found to be very small. Sodium sulfate promoted thicker TGO; more Cr-rich TGO; the formation of Y oxides, and internally, Y sulfides; pore formation in the coating as well as in the substrate; and the formation of a Cr-depleted zone in the substrate.

  • 6.
    Forsberg, Urban
    et al.
    Sandvik Mat Technology, Sweden.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technology, Sweden.
    Hernblom, Johan
    Sandvik Mat Technology, Sweden.
    Peltola, Timo
    Sandvik Mat Technology, Sweden.
    Darley, Glenn
    Sandvik Mat Technology, Sweden.
    UNS S31035/1.4990-a newly developed high strength heat resistant austenitic stainless steel for advanced high efficient coal fired power plants2016Ingår i: ADVANCES IN MATERIALS TECHNOLOGY FOR FOSSIL POWER PLANTS: PROCEEDINGS FROM THE EIGHTH INTERNATIONAL CONFERENCE, 2016, ASM INTERNATIONAL , 2016, s. 310-317Konferensbidrag (Refereegranskat)
    Abstract [en]

    Energy requirement and environmental concerns have promoted a development in higher efficiency coal fired power technologies. Advanced ultra-super critical power plant with an efficiency of higher than 50% is the target in the near future. The materials to be used due to the tougher environments become therefore critical issues. This paper provides a review on a newly developed advanced high strength heat resistant austenitic stainless steel, Sandvik Sanicro 25, for this purpose. The material shows good resistance to steam oxidation and flue gas corrosion, and has higher creep rupture strength than any other austenitic stainless steels available today, and has recently obtained two AMSE code cases. This makes it an interesting option in higher pressures/temperature applications. In this paper, the material development, structure stability, creep strength, steam oxidation and hot corrosion behaviors, fabricability and weldability of this alloy have been discussed. The conclusion is that the Sanicro 25 is a potential candidate for superheaters and reheaters in higher-efficiency coal fired boilers i.e. for applications seeing up to 700 degrees C material temperature.

  • 7. Beställ onlineKöp publikationen >>
    Jonnalagadda, Krisha Praveen
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Failure mechanisms in APS and SPS thermal barrier coatings during cyclic oxidation and hot corrosion2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Thermal Barrier Coatings (TBCs) are advanced material systems that are being used in the hot sections of gas turbines such as combustor, turbine blades, and vanes. The top ceramic coating in TBCs provides insulation against the hot gases and the intermediate metallic bond coat provides oxidation and corrosion resistance to the underlying turbine components.

    Durability of thermal barrier coatings is very important for the overall performance of the gas turbine. TBCs can fail in several different ways and there is a combination of more than one failure mechanism in most situations. One of the most widely used TBC is atmospheric plasma sprayed (APS) yttria stabilized zirconia (YSZ). Both the deposition technique and the TBC material have certain limitations. The main aim of this research is to study new TBC materials and/or new deposition techniques and compare with the conventional YSZ and understand their failure mechanisms during cyclic oxidation and hot corrosion.

    Thermal cyclic oxidation of a newly developed high purity nano YSZ thermal barrier coating has been studied. Cross sectional analysis of exposed as well as completely failed samples showed a mixed-type failure caused by crack propagation parallel to the bond coat/top coat interface. The majority of the damage occurred towards the end of the coating life. A finite element model has been developed to study the probability of crack growth along different paths that leads to the final failure.

    Hot corrosion mechanism in suspension plasma sprayed two-layer gadolinium zirconate/YSZ, three-layer dense gadolinium zirconate/gadolinium zirconate/YSZ, and a single-layer YSZ has been studied in the presence of sodium sulfate and vanadium pentoxide. The test results showed that gadolinium zirconate coatings were more susceptible to corrosion compared to YSZ coatings despite gadolinium zirconate coatings having lower reactivity with the corrosive salts.

    Thermal cycling behavior of a high chromium bond coat has been studied. Cross-sectional analysis showed formation of sandwich type microstructure with chromium rich oxide and alumina as the top and the bottom layers.

    Inter-diffusion of minor elements between different MCrAlY coatings – substrate systems has been studied using, diffusion simulation software, DICTRA. The simulation results showed that the diffusion of minor elements in the coatings is dependent on the rate of β phase depletion in the beginning. After the depletion of β phase there was no clear dependence of the coating composition on the diffusion of minor elements.

    Delarbeten
    1. Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4
    Öppna denna publikation i ny flik eller fönster >>Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4
    Visa övriga...
    2017 (Engelska)Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, nr 1, s. 140-149Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

    Ort, förlag, år, upplaga, sidor
    New York: Springer, 2017
    Nyckelord
    gadolinium zirconatehot corrosionmulti-layer thermal barrier coatingssuspension plasma sprayingvanadium pentoxide + sodium sulfate
    Nationell ämneskategori
    Korrosionsteknik Bearbetnings-, yt- och fogningsteknik Materialkemi
    Identifikatorer
    urn:nbn:se:liu:diva-134375 (URN)10.1007/s11666-016-0486-5 (DOI)000392060300014 ()
    Anmärkning

    Funding agencies: Vinnova in Sweden

    Tillgänglig från: 2017-02-08 Skapad: 2017-02-08 Senast uppdaterad: 2019-02-26Bibliografiskt granskad
    2. Thermal fatigue failure of thermal barrier coatings with a high-Cr MCrAIY bond coat
    Öppna denna publikation i ny flik eller fönster >>Thermal fatigue failure of thermal barrier coatings with a high-Cr MCrAIY bond coat
    Visa övriga...
    2016 (Engelska)Ingår i: Proceedings of the International Thermal Spray Conference (ITSC), 2016, Vol. 324, s. 273-278Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Thermal barrier coatings (TBCs) were air-plasma sprayed onto Hastelloy X substrates. The TBCs consisted of a high-Cr MCrAlY (M for Ni and Co) bond coat and a yttria-stabilized zirconia (YSZ) top coat. The TBC samples were thermally cycled between 100 ºC and 1100 ºC with 1 hour dwell time at 1100 ºC. The thermal fatigue failure of the TBCs was investigated via microstructure analyses. The final fatigue failure of the TBCs was caused by the formation of interface-parallel cracks in the YSZ top coat. The formation of the cracks was found to be strongly related to the oxidation behaviour of the MCrAlY bond coat. The development of the oxide layers was therefore studied in detail. A thermokinetic model was also used to deepen the understanding on the elemental diffusion behavior in the materials.

    Nationell ämneskategori
    Bearbetnings-, yt- och fogningsteknik Metallurgi och metalliska material Materialkemi Kompositmaterial och -teknik
    Identifikatorer
    urn:nbn:se:liu:diva-134377 (URN)
    Konferens
    International Thermal Spray Conference (ITSC), May 10-12, 2016, China
    Tillgänglig från: 2017-02-08 Skapad: 2017-02-08 Senast uppdaterad: 2017-02-16Bibliografiskt granskad
  • 8.
    Jonnalagadda, Krisha Praveen
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Mahade, Satyapal
    Department of Engineering ScienceUniversity West, Trollhättan, Sweden.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicolaie
    Department of Engineering Science University West, Trollhättan, Sweden.
    Nylén, Per
    Department of Engineering Science University West, Trollhättan, Sweden.
    Björklund, Stefan
    Department of Engineering Science University West, Trollhättan, Sweden.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO42017Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, nr 1, s. 140-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

  • 9.
    Jonnalagadda, Krishna Praveen
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Thermal Barrier Coatings: Failure Mechanisms and Life Prediction2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Thermal barrier coatings (TBCs) use in the hot sections of gas turbine engine enables them to run at higher temperatures, and as a consequence, achieve higher thermal efficiency. For full operational exploitation of TBCs, understanding their failure and knowing the service life is essential. The broad objective of the current research is to study the failure mechanisms of new TBC materials and deposition techniques during corrosion and thermal cycling and to develop life models capable of predicting the final failure during thermal cycling.

    Yttria-stabilized zirconia (YSZ) has constraints such as limited operation temperature, despite being the current industry standard. Pyrochlores of A2B2O7 type have been suggested as a potential replacement for YSZ and were studied in this work. Additionally, improvements to the conventional YSZ in the form of nanostructured YSZ were also explored. The requirement for the new deposition process comes from the fact that the existing low-cost deposition processes, like atmospheric plasma spray (APS), generally exhibit lower strain tolerance. A relatively new technique, suspension plasma spray (SPS), known to be promising with better strain tolerance, has been studied in this work.

    At the gas turbine operating conditions, TBCs degrade and eventually fail. Common failure observed in gas turbines can be due to corrosion, thermal mismatch between the ceramic and the metallic layers, and bond coat oxidation during thermal cycling. SPS and APS TBCs were subjected to different test conditions to understand their corrosion behavior. A study on the multi-layered SPS TBCs in the presence of V2O5+Na2SO4 showed that YSZ based SPS coatings were less susceptible to corrosion damage compared to Gd2Zr2O7 SPS TBCs. A study on the influence of a sealing layer in multi-layered SPS TBCs in the presence of Na2SO4+NaCl showed that the sealing layer is ineffective if the material used for sealing is inert to the molten salts. A new study on the influence of corrosion, caused by a mixed-gas atmosphere, on the thermal cycling fatigue life of SPS TBCs was conducted. Results showed that corrosive products grew inside the top coat close to the bond coat/top coat interface along with accelerated growth of alumina. These, together, reduced the TCF life of corrosion exposed samples significantly. Finally, a study on the influence of salt concentration and temperature on a thin (dense) and a thick (porous) coating showed that thick and porous coatings have lower corrosion resistance than the thin and dense coatings. Additionally, a combination of low temperature and high salt concentration was observed to cause more damage.

    Thermal cycling studies were done with the objective of understanding the failure mechanisms and developing a life model. A life model based on fracture mechanics approach has been developed by taking into account different crack growth paths during thermal cycling, sintering of the top coat, oxidation of the bond coat and the thermal mismatch stresses. Validation of such a life model by comparing to the experimental results showed that the model could predict the TCF life reasonably well at temperatures of 1100 °C or below. At higher temperatures, the accuracy of the model became worse. As a further development, a simplified crack growth model was established. This simplified model was shown to be capable of predicting the TCF life as well as the effect of hold times with good accuracy.

    Delarbeten
    1. Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4
    Öppna denna publikation i ny flik eller fönster >>Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4
    Visa övriga...
    2017 (Engelska)Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, nr 1, s. 140-149Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

    Ort, förlag, år, upplaga, sidor
    New York: Springer, 2017
    Nyckelord
    gadolinium zirconatehot corrosionmulti-layer thermal barrier coatingssuspension plasma sprayingvanadium pentoxide + sodium sulfate
    Nationell ämneskategori
    Korrosionsteknik Bearbetnings-, yt- och fogningsteknik Materialkemi
    Identifikatorer
    urn:nbn:se:liu:diva-134375 (URN)10.1007/s11666-016-0486-5 (DOI)000392060300014 ()
    Anmärkning

    Funding agencies: Vinnova in Sweden

    Tillgänglig från: 2017-02-08 Skapad: 2017-02-08 Senast uppdaterad: 2019-02-26Bibliografiskt granskad
    2. Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C
    Öppna denna publikation i ny flik eller fönster >>Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C
    Visa övriga...
    2019 (Engelska)Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, nr 1-2, s. 212-222Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The current investigation focuses on understanding the influence of a columnar microstructure and a sealing layer on the corrosion behavior of suspension plasma sprayed thermal barrier coatings (TBCs). Two different TBC systems were studied in this work. First is a double layer made of a composite of gadolinium zirconate + yttria stabilized zirconia (YSZ) deposited on top of YSZ. Second is a triple layer made of dense gadolinium zirconate deposited on top of gadolinium zirconate + YSZ over YSZ. Cyclic corrosion tests were conducted between 25 and 900 °C with an exposure time of 8 h at 900 °C. 75 wt.% Na2SO4 + 25 wt.% NaCl were used as the corrosive salts at a concentration of 6 mg/cm2. Scanning electron microscopy analysis of the samples’ cross sections showed that severe bond coat degradation had taken place for both the TBC systems, and the extent of bond coat degradation was relatively higher in the triple-layer system. It is believed that the sealing layer in the triple-layer system reduced the number of infiltration channels for the molten salts which resulted in overflowing of the salts to the sample edges and caused damage to develop relatively more from the edge.

    Nyckelord
    columnar microstructure, composite of gadolinium zirconate and YSZ, hot corrosion, suspension plasma spray
    Nationell ämneskategori
    Bearbetnings-, yt- och fogningsteknik
    Forskningsämne
    TEKNIK, Produktions- och materialteknik; Produktionsteknik
    Identifikatorer
    urn:nbn:se:liu:diva-154778 (URN)10.1007/s11666-018-0780-5 (DOI)000456599500019 ()2-s2.0-85055998259 (Scopus ID)
    Forskningsfinansiär
    VINNOVA
    Anmärkning

    This article is an invited paper selected from presentations at the 2018 International Thermal Spray Conference, held May 7-10, 2018, in Orlando, Florida, USA, and has been expanded from the original presentation.

    Tillgänglig från: 2018-11-06 Skapad: 2019-02-26 Senast uppdaterad: 2019-02-26
    3. Factors Affecting the Performance of Thermal Barrier Coatings in the Presence of V2O5 and Na2SO4
    Öppna denna publikation i ny flik eller fönster >>Factors Affecting the Performance of Thermal Barrier Coatings in the Presence of V2O5 and Na2SO4
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    2016 (Engelska)Ingår i: JOURNAL OF CERAMIC SCIENCE AND TECHNOLOGY, ISSN 2190-9385, Vol. 7, nr 4, s. 409-415Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This study investigates the influence of temperature, salt concentration and thickness on the corrosion resistance of seven YSZ thermal barrier coatings in the presence of V2O5 and Na2SO4. For this study, a thick, high-porosity APS coating (670 gm) using hollow spherical powder (HOSP) and a thin, low-porosity APS coating (300 pm) using agglomerated and sintered (Aamp;S) powder were fabricated. Corrosion tests were conducted at 750 degrees C and 900 degrees C with a mixture of Na2SO4 and V2O5 for four hours. At each temperature, salt concentrations of 4,10 and 20 mg/cm(2) were used. SEM and XRD investigations after the corrosion tests revealed that a combination of low temperature and high salt concentration resulted in higher corrosion-induced damage to the thin TBC coatings. With regard to the thick TBC coatings, all except one sample failed during the corrosion test. This suggests that thick TBC coatings with higher porosity may not be suitable in corrosive environments.

    Ort, förlag, år, upplaga, sidor
    GOLLER VERLAG GMBH, 2016
    Nyckelord
    HOSP; agglomerated and sintered YSZ; hot corrosion; TBC
    Nationell ämneskategori
    Materialkemi
    Identifikatorer
    urn:nbn:se:liu:diva-134310 (URN)10.4416/JCST2016-00058 (DOI)000391246300013 ()
    Anmärkning

    Funding Agencies|Vinnova, Sweden

    Tillgänglig från: 2017-02-06 Skapad: 2017-02-03 Senast uppdaterad: 2019-02-26Bibliografiskt granskad
    4. A study of damage evolution in high purity nano TBCs during thermal cycling: A fracture mechanics based modelling approach
    Öppna denna publikation i ny flik eller fönster >>A study of damage evolution in high purity nano TBCs during thermal cycling: A fracture mechanics based modelling approach
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    2017 (Engelska)Ingår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 37, nr 8, s. 2889-2899Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This work concerns the study of damage evolution in a newly developed high purity nano 8YSZ thermal barrier coating during thermal cyclic fatigue tests (TCF). TCF tests were conducted between 100 degrees C-1100 degrees C with a hold time of 1 hat 1100 degrees C, first till failure and later for interrupted tests. Cross section analysis along the diameter of the interrupted test samples revealed a mixed-type failure and that the most of the damage occurred towards the end of the coatings life. To understand the most likely crack growth mechanism leading to failure, different crack growth paths have been modelled using finite element analysis. Crack growing from an existing defect in the top coat towards the top coat/TGO interface has been identified as the most likely mechanism. Estimated damage by the model could predict the rapid increase in the damage towards the end of the coatings life. (C) 2017 Elsevier Ltd. All rights reserved.

    Ort, förlag, år, upplaga, sidor
    ELSEVIER SCI LTD, 2017
    Nyckelord
    Thermal cyclic fatigue; High purity nano YSZ; Crack growth modelling; Damage evolution
    Nationell ämneskategori
    Materialkemi
    Identifikatorer
    urn:nbn:se:liu:diva-137827 (URN)10.1016/j.jeurceramsoc.2017.02.054 (DOI)000400531500015 ()
    Anmärkning

    Funding Agencies|Vinnova in Sweden

    Tillgänglig från: 2017-06-02 Skapad: 2017-06-02 Senast uppdaterad: 2019-02-26
    5. Comparison of Damage Evolution During Thermal Cycling in a High Purity Nano and Conventional Thermal Barrier Coating
    Öppna denna publikation i ny flik eller fönster >>Comparison of Damage Evolution During Thermal Cycling in a High Purity Nano and Conventional Thermal Barrier Coating
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    2017 (Engelska)Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, s. 47-56Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Thermal barrier coatings (TBCs), consisting of a ceramic top coat and a metallic bond coat, offer resistance against high temperature degradation of turbine components. Cyclic oxidation of the bond coat, thermal stresses due to their thermal mismatches during cyclic operations, and sintering of the top coat are considered to be the common ways by which thermal barrier coatings fail. To reduce sintering, a nano structured high purity yttria stabilized zirconia (YSZ) was developed. The focus of this work is to compare the damage development of such high purity nano YSZ TBC during thermal cycling with a conventional YSZ TBC. Thermal cyclic fatigue (TCF) tests were conducted on both the TBC systems between 100 °C and 1100 °C with a 1 h hold time at 1100 °C. TCF test results showed that conventional YSZ TBC exhibited much higher life compared to the high purity nano YSZ TBC. The difference in the lifetime is explained by the use of microstructural investigations, crack length measurements along the cross-section and the difference in the elastic modulus. Furthermore, stress intensity factors were calculated in order to understand the difference(s) in the damage development between the two TBC systems.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2017
    Nyckelord
    High purity nano, damage evolution, thermal cycling fatigue, crack length measurement, conventional TBC
    Nationell ämneskategori
    Materialteknik
    Identifikatorer
    urn:nbn:se:liu:diva-142311 (URN)10.1016/j.surfcoat.2017.09.069 (DOI)000418968100007 ()2-s2.0-85030751243 (Scopus ID)
    Anmärkning

    Funding agencies: Vinnova in Sweden [2015-06870]

    Tillgänglig från: 2017-10-25 Skapad: 2017-10-25 Senast uppdaterad: 2019-02-26Bibliografiskt granskad
    6. Thermal barrier coatings: Life model development and validation
    Öppna denna publikation i ny flik eller fönster >>Thermal barrier coatings: Life model development and validation
    2019 (Engelska)Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 362, s. 293-301Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The failure of thermal barrier coatings (TBCs) during thermal cyclic fatigue (TCF) tests depends mainly on the thermal mismatch between the coating and the substrate, the thermally grown oxides (TGO) at the top coat-bond coat interface, and the sintering of the top coat. Understanding the interplay between these factors is essential for developing a life model. The present work focuses on further development of a previously established fracture mechanics based life model and its validation by comparing with the experimental results. The life model makes use of a Paris' law type equation to estimate the cycles to failure based on micro-crack growth. The fitting parameters for the Paris' law were obtained from the experimentally measured crack lengths after the interruption of TCF tests at different cycles. An alternative approach to obtain the fitting parameters through video monitoring was also discussed. It is shown that regardless of the approach to obtain the fitting parameters, the life model in its current form is able to predict the TCF life at different temperatures with reasonable accuracy. However, at very high temperatures (1150 °C) the predictive capabilities of the model appeared to be poor.

    Nyckelord
    Thermal barrier coatings, Thermal cyclic fatigue, Life modeling, Life prediction
    Nationell ämneskategori
    Bearbetnings-, yt- och fogningsteknik
    Identifikatorer
    urn:nbn:se:liu:diva-154779 (URN)10.1016/j.surfcoat.2019.01.117 (DOI)000461526400035 ()
    Anmärkning

    Funding agencies: VINNOVA in Sweden

    Tillgänglig från: 2019-02-26 Skapad: 2019-02-26 Senast uppdaterad: 2019-04-03
    7. Fatigue life prediction of thermal barrier coatings using a simplified crack growth model
    Öppna denna publikation i ny flik eller fönster >>Fatigue life prediction of thermal barrier coatings using a simplified crack growth model
    2019 (Engelska)Ingår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 39, nr 5, s. 1869-1876Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Models that can predict the life of thermal barrier coatings (TBCs) during thermal cycling fatigue (TCF) tests are highly desirable. The present work focuses on developing and validating a simplified model based on the relation between the energy release rate and the TCF cycles to failure. The model accounts for stresses due to thermal mismatch, influence of sintering, and the growth of TGO (alumina and other non-protective oxides). The experimental investigation of TBCs included; 1) TCF tests at maximum temperatures of 1050 °C, 1100 °C, 1150 °C and a minimum temperature of 100 °C with 1 h and 5 h (1100 °C) hold times. 2) Isothermal oxidation tests at 900, 1000 and 1100 °C for times up to 8000 h. The model was calibrated and validated with the experimental results. It has been shown that the model is able to predict the TCF life and effect of hold time with good accuracy.

    Nyckelord
    Thermal barrier coatings, Thermal cycling fatigue, Life prediction model, Energy release rate
    Nationell ämneskategori
    Bearbetnings-, yt- och fogningsteknik
    Identifikatorer
    urn:nbn:se:liu:diva-154780 (URN)10.1016/j.jeurceramsoc.2018.12.046 (DOI)000459950700016 ()
    Anmärkning

    Funding agencies: Vinnova in Sweden

    Tillgänglig från: 2019-02-26 Skapad: 2019-02-26 Senast uppdaterad: 2019-03-20
  • 10.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Yuan, Kang
    Beijing Gen Res Inst Min and Met, Peoples R China.
    Li, Xin-Hai
    Siemens Ind Turbomachinery AB, Sweden.
    Ji, Xiaojuan
    Beijing Gen Res Inst Min and Met, Peoples R China.
    Yu, Yueguang
    Beijing Gen Res Inst Min and Met, Peoples R China.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Influence of Top Coat and Bond Coat Pre-Oxidation on the Corrosion Resistance of Thermal Barrier Coatings in the Presence of SO22018Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 6, AMER SOC MECHANICAL ENGINEERS , 2018, artikel-id V006T24A018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thermal barrier coatings (TBCs) degradation due to corrosion is one of the commonly observed failure types in land-based gas turbines due to the usage of low grade fuels. Sulfur in its gaseous form, as SO2, can attack the TBC system and result in the degradation of both the coating and the turbine component. The present study aims to understand the difference in the corrosion induced damage caused by SO2 gas mixture in different coating architectures. Corrosion tests were conducted at 780 degrees C in a tube furnace for a period of 168h. The inlet test gas had a composition of 1SO(2)-0.1CO-20CO(2)-N-2 (bal.) in vol. %. The coating architectures consisted of 1) an overlay coating, 2) a single-side bond coat TBC, 3) an all-side bond coat TBC, 4) an all-side bond coat TBC subjected to pre-oxidation prior to the corrosion tests. The results from the corrosion tests showed that the damage was the most severe for the overlay followed by single-side bond coat TBC. Between the other two systems, the TBC subjected to pre-oxidation had relatively lower corrosion damage. The corrosion damage started from the edges for the overlay and single-side bond coat TBC and as well as through the penetration of the gas through the coating. For the coatings with bond coat on all sides, the edge damage appeared to be considerably reduced and the damage is predominantly through the gas infiltration.

  • 11.
    Liang, Jiamin
    et al.
    Tianjin Univ, Peoples R China; Chinese Acad Sci, Peoples R China.
    Wei, Qiang
    Tianjin Univ, Peoples R China; Hebei Univ Technol, Peoples R China.
    Ge, Fangfang
    Chinese Acad Sci, Peoples R China.
    Ren, Donglou
    Chinese Acad Sci, Peoples R China.
    Wang, Ji
    Chinese Acad Sci, Peoples R China.
    Dong, Yue
    Chinese Acad Sci, Peoples R China.
    Eklund, Per
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Huang, Feng
    Chinese Acad Sci, Peoples R China.
    Du, Shiyu
    Chinese Acad Sci, Peoples R China.
    Huang, Qing
    Chinese Acad Sci, Peoples R China.
    Synthesis of Zr2Al3C4 coatings on zirconium-alloy substrates with Al-C/Si interlayers as diffusion barriers2019Ingår i: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 160, s. 128-132Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Zr2Al3C4 coatings are potential candidates to prevent claddings of traditional Zr-based alloys from severe oxidation in water steam at high temperature. However, the diffusion of aluminum between coating and substrates at high temperature results in a coating composition deviating from the compositional domain for formation of the Zr2Al3C4 phase. Thus, synthesis of Zr2Al3C4 coatings on zirconium-alloy substrates is challenging. Here, we report that the Zr2Al3C4 phase can be obtained on zirconium alloy (ZIRLO) substrates where an Al-C/Si interlayer deposited by magnetron sputtering is introduced. The Al-C/Si interlayer prevented elemental diffusion of aluminum between the Zr-Al-C coating and the substrates during a post-annealing process at 800 degrees C for 3 h. The Al/Zr ratio of the Zr-Al-C coating after annealing was 0.96 and 0.59 in the cases of with and without Al-C/Si interlayer, respectively. Hence, the Al-C/Si interlayer acts as diffusion barrier and greatly decreases the deviation from the standard stoichiometric ratio of the Zr2Al3C4 phase, which facilitates the formation of the Zr2Al3C4 phase in the final coating.

    Publikationen är tillgänglig i fulltext från 2020-11-16 15:47
  • 12.
    Yuan, Kang
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    Li, Xin-Hai
    Finspang, Sweden.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    Hot Corrosion Behavior of HVOF-sprayed CoNiCrAlYSi Coatings in a Sulphate Environment2015Ingår i: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 122, nr part A, s. 47-53Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    HVOF-sprayed CoNiCrAlYSi coatings were tested at 900 °C in a hot corrosion environment containing sodium–potassium sulphates. The HVOF spraying caused the typical splat-on-splat structure. The results after the hot corrosion testing showed that the corrosion preferentially occurred at the coating surface and the splat boundaries. The oxidation along the splat boundaries can isolate the splat from the underlying coating matrix. In those isolated splats or coating parts, internal oxidation and nitridation of Al took place, following that the Al-depleted coating fragments were then oxidized to spinels. For those coatings which had a worse splat boundary quality (i.e. with higher porosity and intersplat oxides) or had a worse coating surface quality (i.e. with more small coating fragments therefore more interfaces), heavier corrosion attack was observed on those coatings due to the corrosion of the splats or the coating fragments. The results indicated that the as-sprayed coating quality including porosity and surface morphology was important for the hot-corrosion resistance of the coatings.

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