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  • 1.
    Brodin, Håkan
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Aspects of fatigue life in thermal barrier coatings2001Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thermal barrier coatings (TBC) are applied on hot components in airborne and land-based gas turbines when higher turbine inlet temperature, meaning better thermal efficiency, is desired. The TBC is mainly applied to protect underlying material from high temperatures, but also serves as a protection from the aggressive corrosive environment.

    Plasma sprayed coatings are often duplex TBC's with an outer ceramic top coat (TC) made from partially stabilised zirconia - ZrO2 + 6-8% Y2O3. Below the top coat there is a metallic bond coat (BC). The BC is normally a MCrAlX coating (M=Ni, Co, Fe ... and X=Y, Hf, Si ... ). In gas turbine components exposed to elevated temperatures nickel-based superalloys are commonly adopted as load carrying components. In the investigations performed here a commercial wrought Ni-base alloy Haynes 230 has been used as substrate for the TBC. As BC a NiCoCrAlY serves as a reference material and in all cases 7% yttria PS zirconia has been used. Phase development and failure mechanisms in APS TBC during service-like conditions have been evaluated in the present study. This is done by combinations of thermal cycling and low cycle fatigue tests. The aim is to achieve better knowledge regarding how, when and why thermal ban'ier coatings fail. As a fmal outcome of the project a model capable of predicting fatigue life of a given component will help engineers and designers of land based gas turbines for power generation to better optimise TBC's.

    In the investigations it is seen that TBC life is strongly influenced by oxidation of the BC and interdiffusion between BC and the substrate. The bond coat is known to oxidise with time at high temperature. The initial oxide found during testing is alumina. With increased time at high temperature Al is depleted from the bond coat due to interdiffusion and oxidation. Oxides others than alumina start to form when the Al content is reduced below a critical limit. It is here believed that spinel appears when the Al content is lowered below 2w/o in the bond coat. Here it was shown that a faster growing oxide, rich in Ni, Cr and Co forms at the interface. Al depletion is also linked to BC phases. Initially the bond coat is a γ/ß-material possibly with very fine dispersed γ'. Simultaneously with Al-depletion the ß-phase is found to disappear. This occurs simultaneously with the formation of spinel. However, oxidation is not only a disadvantage. Low cycle fatigue tests reveal that oxide streaks within the bond coat will slow down crack growth due to crack deflection and crack branching. Therefore benefit of or damage from oxide growth on crack initiation and propagation is dependent on crack mode, spalling of the ceramic TC or growth of "classic" cracks perpendicular to the surface.

    From the observations conclusions are drawn regarding fatigue behaviour ofTBC systems. The basic idea is that all cracks leading to failure initiate in the thermally grown oxide (TGO). Following the initiation, they can, however, grow to form either delamination cracks leading to top coat spallation or cracks transverse to the surface leading to component failure.

    List of papers
    1. Behaviour of a Thermal Barrier Coating during High Temperature Oxidation
    Open this publication in new window or tab >>Behaviour of a Thermal Barrier Coating during High Temperature Oxidation
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    An air plasma sprayed thermal barrier coating was investigated in order to clarify links between heat treatment, oxidation and diffusion behaviour. In the study a thin Zirconia (PSZ) layer was used as top coat together with a NiCoCrAlY bond coat. The investigation was focused on differences for three geometries. Thermal barrier coatings on flat, concave and convex surfaces were studied. Isothermal oxidation was performed up to 1000 hrs at 1000°C in order to simulate true working conditions for the interface between ceramic top coat and metallic bond coat. The investigations show presence of Al-rich oxides for shorter times. When the coating system is heat-treated for 1000 hrs a change of oxide composition is obvious and beside Al the oxides contain Ni, Cr and Co. The oxides tend to grow with different rates depending on the macroscopic surface geometry. In the study convex surfaces reveal the highest oxide growth rates and concave the lowest growth rates. At 1000 hrs and 1000°C the difference between the fastest and the slowest growing oxide layer is 1 μm. Some interdiffusion is obvious. Between the superalloy substrate and the bond coat outward diffusion of Ni, W and Cr is present together with inward diffusion of Co and to some extent Al.

    Keywords
    APS, thermal barrier coating, oxidation, growth rate, NiCoCrAlY, geometry
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-102045 (URN)
    Available from: 2013-11-28 Created: 2013-11-28 Last updated: 2013-11-28
    2. Crack initiation and propagation in air plasma sprayed thermal barrier coatings, testing and mathematical modelling of low cycle fatigue behaviour
    Open this publication in new window or tab >>Crack initiation and propagation in air plasma sprayed thermal barrier coatings, testing and mathematical modelling of low cycle fatigue behaviour
    2004 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 379, no 1-2, p. 45-57Article in journal (Refereed) Published
    Abstract [en]

    In the present paper failure mechanisms in air plasma sprayed thermal barrier coatings for land-based gas turbines have been studied. This has been done by finite element simulations and fractographic investigations of low cycle fatigue (LCF) tested material, here chosen as an 350 μm thick partially stabilised zirconia top coat (TC) together with a 150 μm thick Ni-Co-Cr-Al-Y bond coat (BC) on a nickel base substrate (Haynes 230). Both LCF testing, modelling results and fractographic investigations point in the same direction. An increased thickness of the thermally grown oxide (TGO) does decrease the LCF life of a coated structural alloy. Several points of crack initiation were found, in the TGO at the TC/BC interface, at the oxide network within the BC and at oxide inclusions between BC and substrate. During LCF tests the initiated cracks will grow radially into the substrate material. The behaviour is explained by increased TC/BC delamination stresses and changed oxidation behaviour with increased oxidation times.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-22790 (URN)10.1016/j.msea.2003.12.063 (DOI)2123 (Local ID)2123 (Archive number)2123 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
    3. Bond Coat Influence on TBC Life
    Open this publication in new window or tab >>Bond Coat Influence on TBC Life
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    In the present study the influence of bond coat composition and coating process on thermal barrier coating (TBC) life has been evaluated. Six different coatings have been subjected to thermal cycling between 100 and 1100°C. After this the different systems have been characterised by light microscopy and SEM-EDS. Various commercial bond coats have been applied on one substrate material (Haynes alloy 230). The total fatigue life of the different TBC systems varies with 30% what is believed to be influenced by diffusion and oxidation phenomena in the bond coat. It is found that when the aluminium concentration is decreased phases other than alumina form at the top coat I bond coat interface. Oxides formed during later stages of the thermal cyclic test are rich in nickel, cobalt and chromium and the results can be interpreted as formation of nickel-, chromium- or spinel oxides. The reason for TBC failure is coupled to aluminium depletion, which here is believed to be due to inward diffusion and formation of thermally grown oxides (TGO) at the ceramic top coat (TC) metallic bond coat (BC) interface as well as growth of internal oxides in the bond coat.

    Keywords
    thermal barrier coating, NiCoCrAIY, CoNiCrAIY, alumina, thermal fatigue, oxide growth, interdiffusion
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-102046 (URN)
    Available from: 2013-11-28 Created: 2013-11-28 Last updated: 2013-11-28
  • 2.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Delamination damage development in thermal barrier coatings2004In: Brinellkonferens,2004, 2004Conference paper (Other academic)
  • 3.
    Brodin, Håkan
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Failure of thermal barrier coatings under thermal and mechanical fatigue loading: microstructural observations and modelling aspects2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Industrial and air-borne gas turbine hot components suffer from creep, oxidation, corrosion and microstructural degradation if not shielded from the hot and aggressive combustion gases. Two major strategies commercially available are adopted; film cooling by pressurised air and application of protective coatings. Protective coatings form a slow-growing oxide that protects from oxidation and corrosion. By application of a thermal insulator, a thermal barrier coating, the material will be protected from high temperature through good insulation properties of the coating system.

    If thermal barrier coatings are to be used in situations where capabilities and possibilities for inspections are limited, better knowledge of the fatigue properties of the coatings is also needed. Therefore development of a reliable fatigue life model is needed. The present work aims at serving as a basis from which a general physically founded thermal barrier coating life model can be formulated. The effects of exposure to high temperatures and mechanical loads on thermal barrier coatings under service like conditions have been investigated in the present thesis. Emphasis is put on the coupling between materials science and solid mechanics approaches in order to establish a better knowledge concerning degradation mechanisms and fatigue life issues than what is common if only one discipline is explored.

    Investigations of material exposed to isothermal oxidation and thermal cyclic fatigue were performed on plasma-sprayed systems with NiCoCrAIY or NiCrAIY bond coats and yttria partially stabilised zirconia top coats. It has been shown that the thermally grown oxide that will form upon high temperature exposure influences the failure behaviour. If the oxide is composed mainly of alumina, the fatigue properties are good since the adhesion between the ceramic top coat and the metallic bond coat is good. This is also shown in a comparison between different plasma sprayed thermal barrier coating systems. If the oxide formed is based on alurnina and spinel is avoided the fatigue properties benefit from a relatively flat interface where out-of plane stresses are low in comparison to a rough interface between top- and bond coat. These findings indicate that the bonding in air-plasma sprayed systems is dependent on so called chemical bonding if the thermally grown oxide is not voluminous with high growth stresses.

    It is possible to establish a fatigue life model for thermal barrier coatings. This has been shown with a model based on a modified Paris law formulation. The formulation needs to be modified with regards to mode rnixity of growth. Results achieved in the present project show that it is possible to extract crack growth data for interfacial crack growth. However a combination of mechanical testing and finite element modelling is needed since the load situation in critical areas cannot be measured. Crack growth results are presented and crack growth data are compared to predictions with good agreement.

    List of papers
    1. Influence of high temperature exposure on thermal barrier coating behaviour
    Open this publication in new window or tab >>Influence of high temperature exposure on thermal barrier coating behaviour
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    An air plasma sprayed thermal barrier coating was investigated in order to clarify links between heat treatment, oxidation and diffusion behaviour. In the study a thin Zirconia (PSZ) layer was used as top coat together with a NiCoCrAIY bond coat. The investigation was focused on differences for three geometries. Thermal barrier coatings on flat, concave and convex surfaces were studied. Isothermal oxidation was performed up to 1000 hrs at 1000°C in order to simulate true working conditions for the interface between ceramic top coat and metallic bond coat. The investigations show presence of Al-rich oxides for shorter times. When the coating system is heat-treated for 1000 hrs a change of oxide composition is obvious and beside AI the oxides contain Ni, Cr and Co. The oxides tend to grow with different rates depending on the macroscopic surface geometry. In the study concave surfaces reveal the highest oxide growth rates and convex the lowest growth rates. At 1000 hrs and 1 000°C the difference between the fastest and the slowest growing oxide layer is 1µm. Some interdiffusion is obvious. Between the superalloy substrate and the bond coat outward diffusion of Ni, W and Cr is present together with inward diffusion of Co and to some extent Al.

    Keywords
    APS, thermal barrier coating, oxidation, growth rate, NiCoCrAlY, geometry
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-88205 (URN)
    Available from: 2013-01-31 Created: 2013-01-31 Last updated: 2013-01-31
    2. Crack initiation and propagation in air plasma sprayed thermal barrier coatings, testing and mathematical modelling of low cycle fatigue behaviour
    Open this publication in new window or tab >>Crack initiation and propagation in air plasma sprayed thermal barrier coatings, testing and mathematical modelling of low cycle fatigue behaviour
    2004 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 379, no 1-2, p. 45-57Article in journal (Refereed) Published
    Abstract [en]

    In the present paper failure mechanisms in air plasma sprayed thermal barrier coatings for land-based gas turbines have been studied. This has been done by finite element simulations and fractographic investigations of low cycle fatigue (LCF) tested material, here chosen as an 350 μm thick partially stabilised zirconia top coat (TC) together with a 150 μm thick Ni-Co-Cr-Al-Y bond coat (BC) on a nickel base substrate (Haynes 230). Both LCF testing, modelling results and fractographic investigations point in the same direction. An increased thickness of the thermally grown oxide (TGO) does decrease the LCF life of a coated structural alloy. Several points of crack initiation were found, in the TGO at the TC/BC interface, at the oxide network within the BC and at oxide inclusions between BC and substrate. During LCF tests the initiated cracks will grow radially into the substrate material. The behaviour is explained by increased TC/BC delamination stresses and changed oxidation behaviour with increased oxidation times.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-22790 (URN)10.1016/j.msea.2003.12.063 (DOI)2123 (Local ID)2123 (Archive number)2123 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
    3. The influence of oxidation on mechanical and fracture behaviour of an air plasma-sprayed NiCoCrAlY bondcoat
    Open this publication in new window or tab >>The influence of oxidation on mechanical and fracture behaviour of an air plasma-sprayed NiCoCrAlY bondcoat
    2004 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 187, no 1, p. 113-121Article in journal (Refereed) Published
    Abstract [en]

    The influence of isothermal oxidation on room-temperature mechanical and fracture behaviour of an air plasma-sprayed Ni-23Co-17Cr-12Al-0.5Y bondcoat was investigated by the miniaturised disc bending test (MDBT) technique. Disc specimens were extracted from the bondcoat region of both as-received and oxidised thermal barrier coating (1000 °C, 1000 h). Microstructure analysis revealed that the non-oxidised bondcoat consisted mainly of γ-phase (Ni-structure) and β-NiAl. After 500 h of oxidation no NiAl remained in the bondcoat, an effect due to internal as well as external oxidation of Al. The former resulted in the formation of an extensive oxide network and the latter in the formation of an oxide scale between the topcoat and the bondcoat. The crack propagation behaviour of the bondcoat, both in non-oxidised and oxidised condition can be characterised as intergranular with stable growth. The crack propagation resistance is substantial due to the lamellar grain (splat) orientation and the extensive intergranular oxide network, acting as crack deflection and crack branching mechanisms. As an effect of oxidation, crack propagation resistance of the bondcoat increases but the strain to crack initiation decreases.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-22777 (URN)10.1016/j.surfcoat.2003.12.021 (DOI)2108 (Local ID)2108 (Archive number)2108 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
    4. Bond coat influence on thermal fatigue behaviour of thermal barrier coatings
    Open this publication in new window or tab >>Bond coat influence on thermal fatigue behaviour of thermal barrier coatings
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    In the present study the influence of bond coat composition and coating process on thermal barrier coating (TBC) life has been evaluated. Six different coatings have been subjected to thermal cycling between 100 and 1100°C. After this the different systems have been characterised by light microscopy and SEM-EDS. Various commercial bond coats have been applied on one substrate material (Haynes alloy 230). The total fatigue life of the different TBC systems varies with 30% what is believed to be influenced by diffusion and oxidation phenomena in the bond coat. It is found that when the aluminium concentration is decreased phases other than alumina form at the top coat / bond coat interface. Oxides formed during later stages of the thermal cyclic test are rich in nickel, cobalt and chromium and the results can be interpreted as formation of nickel-, chromium- or spinel oxides. The reason for TBC failure is coupled to aluminium depletion, which here is believed to be due to inward diffusion and formation of thermally grown oxides (TGO) at the ceramic top coat (TC) metallic bond coat (BC) interface as well as growth of internal oxides in the bond coat.

    Keywords
    thermal barrier coating, NiCoCrAlY, CoNiCrAlY, alumina, thermal fatigue, oxide growth, interdiffusion
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-88206 (URN)
    Available from: 2013-01-31 Created: 2013-01-31 Last updated: 2013-01-31
    5. Fatigue life prediction of a plasma sprayed thermal barrier coating system
    Open this publication in new window or tab >>Fatigue life prediction of a plasma sprayed thermal barrier coating system
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Thermal barrier coatings are commonly used in gas turbines for power generation. One major issue in TBC design is how to determine fatigue life in these material systems. The present paper aims at presenting a model for determination of TBC life based on the behavior of an air plasma sprayed coating system. This is done by analysis of fracture behavior and evaluation of data from thermal fatigue tests. The knowledge regarding fracture behavior in thermal fatigue tests is used as an input to the modelling work. For formulation of the fatigue life model, a Paris law approach has been used. FE calculations are used to obtain energy release rate and stress intensity factors, KI and KII, for a propagating delamination crack in the top/ bond coat interface. As a measure of failure, a delamination damage measure is used. A method for determination of delamination crack growth data is presented.

    Keywords
    Thermal barrier coating, delamination, fatigue, fracture mechanics, modelling, crack growth
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-24277 (URN)3886 (Local ID)3886 (Archive number)3886 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-01-31
    6. Initiation and growth of delamination cracks in vacuum plasma sprayed thermal barrier coatings
    Open this publication in new window or tab >>Initiation and growth of delamination cracks in vacuum plasma sprayed thermal barrier coatings
    2004 (English)In: Surface Engineering 2004: Proceedings of the 3rd International Surface Engineering Congress (ASM International), 2004, p. 284-290Conference paper, Published paper (Refereed)
    Abstract [en]

    Thermal barrier coatings are widely used in air-borne and land-based gas turbines. In these applications they serve as thermal insulators in hot components (burner cans/liners, turbine vanes and turbine blades). The present paper is aimed to describe the failure mechanism of a vacuum plasma sprayed thin thermal barrier coating system. Also the coating degradation mechanism (delamination followed by spallation) in terms of interfacial crack growth data is investigated and presented. In the present paper a 200 µm thick NiCrAlY bond coat was chosen together with a 350µm thick 7wt% yttria stabilised zirconia top coat. The coating system was exposed to thermal cyclic fatigue with a thermal cycle ranging from 100 °C to 1100 °C and a cycle time of 70 minutes. After thermal cyclic testing all specimen were subjected to standard sample preparation routines and inspected by optical microscopy and scanning electron microscopy. In order to describe interfacial crack growth an interface damage measure is used. For the present coating system under current thermal load conditions a mainly black interface fracture is discovered. The top coat exhibit microcrack formation after thermal fatigue, but these cracks do not contribute to the final fracture appearance. Crack growth rates are compared to local stress intensity levels at the top coat / bond coat interface. From crack length measurements are crack growth data da/dN = f(ΔKeff) calculated.

    Keywords
    thermal barrier coating, crack growth, delamination, interface, NiCrAlY
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-22779 (URN)2110 (Local ID)0871708191 (ISBN)978-0871708199 (ISBN)2110 (Archive number)2110 (OAI)
    Conference
    3rd International Surface Engineering Conference, Orlando FL, August 2-4 2004
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-01-31
  • 4.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Fatigue crack growth in themal barrier coatings2003In: Brinellkonferens,2003, 2003Conference paper (Other academic)
  • 5.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Fatigue Life in Thermal Barrier Coatings2002In: Alstom RD-dagar 2002,2002, 2002Conference paper (Other academic)
  • 6.
    Brodin, Håkan
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Initiation and growth of delamination cracks in vacuum plasma sprayed thermal barrier coatings2004In: Surface Engineering 2004: Proceedings of the 3rd International Surface Engineering Congress (ASM International), 2004, p. 284-290Conference paper (Refereed)
    Abstract [en]

    Thermal barrier coatings are widely used in air-borne and land-based gas turbines. In these applications they serve as thermal insulators in hot components (burner cans/liners, turbine vanes and turbine blades). The present paper is aimed to describe the failure mechanism of a vacuum plasma sprayed thin thermal barrier coating system. Also the coating degradation mechanism (delamination followed by spallation) in terms of interfacial crack growth data is investigated and presented. In the present paper a 200 µm thick NiCrAlY bond coat was chosen together with a 350µm thick 7wt% yttria stabilised zirconia top coat. The coating system was exposed to thermal cyclic fatigue with a thermal cycle ranging from 100 °C to 1100 °C and a cycle time of 70 minutes. After thermal cyclic testing all specimen were subjected to standard sample preparation routines and inspected by optical microscopy and scanning electron microscopy. In order to describe interfacial crack growth an interface damage measure is used. For the present coating system under current thermal load conditions a mainly black interface fracture is discovered. The top coat exhibit microcrack formation after thermal fatigue, but these cracks do not contribute to the final fracture appearance. Crack growth rates are compared to local stress intensity levels at the top coat / bond coat interface. From crack length measurements are crack growth data da/dN = f(ΔKeff) calculated.

  • 7.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Response of a Thermal Barrier Coating during Heat Treatment2000In: Brinellkonferens,2000, 2000Conference paper (Other academic)
  • 8.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Short time oxidation of a thermal barrier coating1999In: Brinellkonferens,1999, 1999Conference paper (Other academic)
  • 9.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Utmattningslivslängd hos en belagd nickelbaslegering2001In: Svenska mekanikdagarn 2001,2001, 2001Conference paper (Other academic)
  • 10.
    Brodin, Håkan
    et al.
    Linköping University, The Tema Institute. Linköping University, Faculty of Arts and Sciences.
    Andersson, Agneta
    Linköping University, The Tema Institute. Linköping University, Faculty of Arts and Sciences.
    Hälsoekonomins grunder1998Book (Other (popular science, discussion, etc.))
  • 11.
    Brodin, Håkan
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Andersson, Olov
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Mechanical Behaviour and Microstructure Correlation in a Selective Laser Melted Superalloy2013In: ASME Turbo Expo 2013: Turbine Technical Conference and Exposition, American Society of Mechanical Engineers (ASME) , 2013, Vol. 5A, p. 1-7Conference paper (Refereed)
    Abstract [en]

    Selective laser melting (SLM), or, as the industry standard denotes the process, laser sintering, is an additive manufacturing process where metal powder is melted by a laser source layer-wise, forming a solid, dense metallic component. With the SLM process, near net shape components can be manufactured directly from a CAD model. The model is sliced into thin (max 100μm thick) layers. Powder is spread onto a metallic build platform and the powder is fused by a laser as dictated by the CAD model. The laser energy is intense enough to permit full melting (welding) of the particles to form solid metal. The process is repeated layer by layer until the part is complete.

    A number of materials are available, including steel, aluminium, titanium and, in recent time, also superalloys. The material investigated in the current project is an alloy in agreement with the composition of Haynes International Hastelloy X, a solution strengthened superalloy typically used in large welded components exposed to high temperatures in oxidizing as well as reducing environments.

    Microstructurally, the material is different from both a hot-rolled, as well as a cast material due to the manufacturing process. Since the SLM process involves laser melting of powder particles in the size range of <50μm, the structure resembles of a weld structure, however on a smaller scale. Due to the layer-by-layer build strategy, the material will exhibit anisotropy. Different heat treatment approaches can be adopted in order to homogenize the material and to minimize the effect of anisotropy. A stress relieve heat treatment was adopted and compared to the findings of the as manufactured SLM material.

    The current project focuses on evaluating mechanical properties for a material manufactured by the SLM process and comparing to data for established manufacturing processes. For evaluation of the mechanical properties, low cycle fatigue testing and tensile testing has been performed. The microstructure and material deformation / cracking are evaluated by light optical microscopy and SEM, where electron backscatter diffraction is used. Due to the weld-like structure, the material will be transversely isotropic in the as-manufactured condition with one symmetry plane perpendicular to the build direction. Any direction perpendicular to the build direction tends to give increased strength compared to a direction parallel to the build direction if monotonic data are concerned. If fatigue properties are concerned, the anisotropy is also obvious. It is shown that the differences in behaviour can be coupled to microstructure.

  • 12.
    Brodin, Håkan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Ericsson, Torsten
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Behaviour of a Thermal Barrier Coating during High Temperature OxidationManuscript (preprint) (Other academic)
    Abstract [en]

    An air plasma sprayed thermal barrier coating was investigated in order to clarify links between heat treatment, oxidation and diffusion behaviour. In the study a thin Zirconia (PSZ) layer was used as top coat together with a NiCoCrAlY bond coat. The investigation was focused on differences for three geometries. Thermal barrier coatings on flat, concave and convex surfaces were studied. Isothermal oxidation was performed up to 1000 hrs at 1000°C in order to simulate true working conditions for the interface between ceramic top coat and metallic bond coat. The investigations show presence of Al-rich oxides for shorter times. When the coating system is heat-treated for 1000 hrs a change of oxide composition is obvious and beside Al the oxides contain Ni, Cr and Co. The oxides tend to grow with different rates depending on the macroscopic surface geometry. In the study convex surfaces reveal the highest oxide growth rates and concave the lowest growth rates. At 1000 hrs and 1000°C the difference between the fastest and the slowest growing oxide layer is 1 μm. Some interdiffusion is obvious. Between the superalloy substrate and the bond coat outward diffusion of Ni, W and Cr is present together with inward diffusion of Co and to some extent Al.

  • 13.
    Brodin, Håkan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Ericsson, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Behaviour of a Thermal Barrier Coating during High Temperature Oxidation2000In: ASM International Heat Treating Congress,2000, 2000Conference paper (Refereed)
  • 14.
    Brodin, Håkan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Ericsson, Torsten
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of high temperature exposure on thermal barrier coating behaviourManuscript (preprint) (Other academic)
    Abstract [en]

    An air plasma sprayed thermal barrier coating was investigated in order to clarify links between heat treatment, oxidation and diffusion behaviour. In the study a thin Zirconia (PSZ) layer was used as top coat together with a NiCoCrAIY bond coat. The investigation was focused on differences for three geometries. Thermal barrier coatings on flat, concave and convex surfaces were studied. Isothermal oxidation was performed up to 1000 hrs at 1000°C in order to simulate true working conditions for the interface between ceramic top coat and metallic bond coat. The investigations show presence of Al-rich oxides for shorter times. When the coating system is heat-treated for 1000 hrs a change of oxide composition is obvious and beside AI the oxides contain Ni, Cr and Co. The oxides tend to grow with different rates depending on the macroscopic surface geometry. In the study concave surfaces reveal the highest oxide growth rates and convex the lowest growth rates. At 1000 hrs and 1 000°C the difference between the fastest and the slowest growing oxide layer is 1µm. Some interdiffusion is obvious. Between the superalloy substrate and the bond coat outward diffusion of Ni, W and Cr is present together with inward diffusion of Co and to some extent Al.

  • 15.
    Brodin, Håkan
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Eriksson, Robert
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Johansson, Sten
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Fracture Mechanical Modelling of a Plasma Sprayed TBC System2009In: Advanced Ceramic Coatings and Interfaces IV / [ed] Dongming Zhu and Hua-Tay Lin, Westerville, OH, United States: American Ceramic Society Inc. , 2009, Vol. 30, no 3, p. 113-124Conference paper (Refereed)
    Abstract [en]

    A thermal barrier coating (TBC) system subjected to thermal cycling will develop a microcrack partem near the interface between the metallic bond coat and the ceramic top coat. These small cracks link up and form internal TBC delaminations during repeated heating / cooling. After a longer time period, the internal delamination cracks will form a larger spallation damage, where the TBC is detached from the underlying material. Since cracks are initiated in multiple sites of the thermal barrier coating, the damage is initially considered to be governed by local stress conditions. The purpose of the present work is to compare experimental data with predictions of a physically based fatigue life model. The present study has been performed on plasma-sprayed TBCs where the interface geometry has been varied. In the present work, calculation of fatigue life is done for a number of cases under thermal fatigue loading. Different interface geometries are compared in order to understand the influence of variations in the TC/BC interface roughness on oxidation behaviour and thermal fatigue life. Thermal fatigue tests indicate that an increased surface roughness is beneficial from a fatigue life point of view.

  • 16.
    Brodin, Håkan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Eriksson, Robert
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Östergren, Lars
    Volvo Aero Corporation, Trollhättan.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics.
    Finite Element Modelling and Damage Evaluation of Air Plasma Sprayed Thermal Barrier Coatings2012Conference paper (Refereed)
  • 17.
    Brodin, Håkan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Eskner, Mats
    Material Science KTH.
    High Temperature Elastic-Plastic Behaviour of a Vacuum Plasma-Sprayed NiCrAlY Coating by Spherical Indentation and Small Punch Tests1998In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936Article in journal (Refereed)
  • 18.
    Brodin, Håkan
    et al.
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Eskner, Mats
    Department of Materials Science and Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden and Brinell Centre, Stockholm, Sweden.
    The influence of oxidation on mechanical and fracture behaviour of an air plasma-sprayed NiCoCrAlY bondcoat2004In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 187, no 1, p. 113-121Article in journal (Refereed)
    Abstract [en]

    The influence of isothermal oxidation on room-temperature mechanical and fracture behaviour of an air plasma-sprayed Ni-23Co-17Cr-12Al-0.5Y bondcoat was investigated by the miniaturised disc bending test (MDBT) technique. Disc specimens were extracted from the bondcoat region of both as-received and oxidised thermal barrier coating (1000 °C, 1000 h). Microstructure analysis revealed that the non-oxidised bondcoat consisted mainly of γ-phase (Ni-structure) and β-NiAl. After 500 h of oxidation no NiAl remained in the bondcoat, an effect due to internal as well as external oxidation of Al. The former resulted in the formation of an extensive oxide network and the latter in the formation of an oxide scale between the topcoat and the bondcoat. The crack propagation behaviour of the bondcoat, both in non-oxidised and oxidised condition can be characterised as intergranular with stable growth. The crack propagation resistance is substantial due to the lamellar grain (splat) orientation and the extensive intergranular oxide network, acting as crack deflection and crack branching mechanisms. As an effect of oxidation, crack propagation resistance of the bondcoat increases but the strain to crack initiation decreases.

  • 19.
    Brodin, Håkan
    et al.
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Jinnestrand, Magnus
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Fatigue life prediction of a plasma sprayed thermal barrier coating systemManuscript (preprint) (Other academic)
    Abstract [en]

    Thermal barrier coatings are commonly used in gas turbines for power generation. One major issue in TBC design is how to determine fatigue life in these material systems. The present paper aims at presenting a model for determination of TBC life based on the behavior of an air plasma sprayed coating system. This is done by analysis of fracture behavior and evaluation of data from thermal fatigue tests. The knowledge regarding fracture behavior in thermal fatigue tests is used as an input to the modelling work. For formulation of the fatigue life model, a Paris law approach has been used. FE calculations are used to obtain energy release rate and stress intensity factors, KI and KII, for a propagating delamination crack in the top/ bond coat interface. As a measure of failure, a delamination damage measure is used. A method for determination of delamination crack growth data is presented.

  • 20.
    Brodin, Håkan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Jinnestrand, Magnus
    ProTang Mekanikkonsulter AB Västerås.
    Johansson, Sten
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Siemens Industrial Turbomachinery AB Finspång.
    Thermal Barrier Coating Fatigue Life Assessment2006In: Fatigue 2006, 2006Conference paper (Refereed)
  • 21.
    Brodin, Håkan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Jinnestrand, Magnus
    Linköping University, Department of Mechanical Engineering.
    Sjöström, Sören
    Demag Delaval Industrial Turbomachinery AB .
    Fracture-mechanically based modelling of TCF life of thermal barrier coatings2003In: UTMIS Livslängdsdagar 2003,2003, 2003Conference paper (Other academic)
  • 22.
    Brodin, Håkan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Jinnestrand, Magnus
    Linköping University, Department of Mechanical Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Mechanical Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Modelling and experimental verification of delamination crack growth in an air-plasma-sprayed thermal barrier coating2004In: 15th European Conference of Fracture (ECF15), Stockholm, Sweden, 2004, 2004Conference paper (Refereed)
  • 23.
    Brodin, Håkan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Influence on low cycle fatigue properties of bond coat oxidation for a thermal barrier coating2001In: 10th International Congres of Fracture,2001, 2001Conference paper (Refereed)
  • 24.
    Brodin, Håkan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Li, X H
    Demag Delaval Industrial Turbomachinery AB, Finspång.
    Delamination crack growth in thermal barrier coatings2004In: International Thermal Spray Conference and Exposition ITSC2004,2004, 2004Conference paper (Refereed)
  • 25.
    Brodin, Håkan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Li, Xin-Hai
    Alstom Power Sweden, Finspång, Sweden.
    Bond Coat Influence on TBC LifeManuscript (preprint) (Other academic)
    Abstract [en]

    In the present study the influence of bond coat composition and coating process on thermal barrier coating (TBC) life has been evaluated. Six different coatings have been subjected to thermal cycling between 100 and 1100°C. After this the different systems have been characterised by light microscopy and SEM-EDS. Various commercial bond coats have been applied on one substrate material (Haynes alloy 230). The total fatigue life of the different TBC systems varies with 30% what is believed to be influenced by diffusion and oxidation phenomena in the bond coat. It is found that when the aluminium concentration is decreased phases other than alumina form at the top coat I bond coat interface. Oxides formed during later stages of the thermal cyclic test are rich in nickel, cobalt and chromium and the results can be interpreted as formation of nickel-, chromium- or spinel oxides. The reason for TBC failure is coupled to aluminium depletion, which here is believed to be due to inward diffusion and formation of thermally grown oxides (TGO) at the ceramic top coat (TC) metallic bond coat (BC) interface as well as growth of internal oxides in the bond coat.

  • 26.
    Brodin, Håkan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Li, Xin-Hai
    ALSTOM Power Sweden Finspång.
    Bond Coat Influence on TBC Life2002In: Turbin Forum, Advanced Coatings for High Temperatures,2002, 2002Conference paper (Refereed)
  • 27.
    Brodin, Håkan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Li, Xin-Hai
    Demag Delaval Industrial Turbomachinery AB, Finspång, Sweden.
    Bond coat influence on thermal fatigue behaviour of thermal barrier coatingsManuscript (preprint) (Other academic)
    Abstract [en]

    In the present study the influence of bond coat composition and coating process on thermal barrier coating (TBC) life has been evaluated. Six different coatings have been subjected to thermal cycling between 100 and 1100°C. After this the different systems have been characterised by light microscopy and SEM-EDS. Various commercial bond coats have been applied on one substrate material (Haynes alloy 230). The total fatigue life of the different TBC systems varies with 30% what is believed to be influenced by diffusion and oxidation phenomena in the bond coat. It is found that when the aluminium concentration is decreased phases other than alumina form at the top coat / bond coat interface. Oxides formed during later stages of the thermal cyclic test are rich in nickel, cobalt and chromium and the results can be interpreted as formation of nickel-, chromium- or spinel oxides. The reason for TBC failure is coupled to aluminium depletion, which here is believed to be due to inward diffusion and formation of thermally grown oxides (TGO) at the ceramic top coat (TC) metallic bond coat (BC) interface as well as growth of internal oxides in the bond coat.

  • 28.
    Brodin, Håkan
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Li, Xin-Hai
    Siemens Industrial Turbomchinery AB.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Influence on thermal barrier coating delamination behaviour of edge geometry2006Conference paper (Refereed)
  • 29.
    Brodin, Håkan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Saarimäki, Jonas
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Mechanical Properties of Lattice Truss Structures Made of a Selective Laser Melted Superalloy2013Conference paper (Refereed)
  • 30.
    Brodin, Håkan
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Damage development in two thermal barrier coating systems2009In: ICF12,2009, 2009Conference paper (Other academic)
    Abstract [en]

          

  • 31.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Brodin, Håkan
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Östergren, Lars
    GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Cyclic Hot Corrosion of Thermal Barrier Coatings and Overlay Coatings2013In: Proceedings of ASME Turbo Expo 2013: Turbine Technical Conference and Exposition, GT2013, The American Society of Mechanical Engineers (ASME) , 2013, Vol. 4, p. 1-8Conference paper (Refereed)
    Abstract [en]

    The influence, and interdependence, of water vapor and Na2SO4–50 mol% NaCl on the oxidation of a NiCoCrAlY coating and a thermal barrier coating (TBC) were studied at 750 °C. Water vapor was found to have a negligible effect on oxide composition, but influenced the oxide morphology on the NiCoCrAlY coating. Na2SO4–50 mol% NaCl deposits on the coatings influencedoxide composition, most notably by the promotion of a Y rich phase. The effect of Na2SO4–50 mol% NaCl deposits was also evident for the TBC coated specimen, where the formed metal/ceramic interface oxide was affected by salt reaching the interface by penetration of the zirconia TBC.

  • 32.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Brodin, Håkan
    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.
    Östergren, Lars
    Volvo Aero Corporation, Trollhättan, Sweden.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, SE-61283 Finspång, Sweden.
    Fractographic and microstructural study of isothermally and cyclically heat treated thermal barrier coatings2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 243, p. 82-90Article in journal (Refereed)
    Abstract [en]

    The fracture surfaces from adhesion tested thermal barrier coatings (TBC) have been studied by scanning electron microscopy. The adhesion test have been made using the standard method described in ASTM 633, which makes use of a tensile test machine to measure the adhesion. The studied specimens consist of air plasma sprayed (APS) TBC deposited on disc-shaped substrates of Hastelloy X. The bond coat (BC) is of NiCoCrAlY type and the top coat (TC) consists of yttria–stabilised–zirconia. Before the adhesion test, the specimens were subjected to three different heat treatments: 1) isothermal oxidation 2) thermal cycling fatigue (TCF) and 3) burner rig test (BRT). The fracture surfaces of the adhesion tested specimens where characterised. A difference in fracture mechanism were found for the different heat treatments. Isothermal oxidation gave fracture mainly in the top coat while the two cyclic heat treatments gave increasing amount of BC/TC interface fracture with number of cycles. Some differences could also be seen between the specimens subjected to burner rig test and furnace cycling.

  • 33.
    Eriksson, Robert
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Östergren, Lars
    Volvo Aero Corporation, Trollhättan.
    Li, Xin-Hai
    Siemens, Industrial Turbomachinery AB, Finspång.
    Fractographic Study of Adhesion Tested Thermal Barrier Coatings Subjected to Isothermal and Cyclic Heat Treatments2011In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 10, p. 195-200Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBC) are used in gas turbines to protect metallic components from high temperature. In the present study adhesion tests have been conducted on APS TBC coated specimens subjected to different heat treatments. Isothermal and cyclic heat treatments have been conducted at temperatures around 1100 °C and the adhesion have been tested using the method described in ASTM C633. The fracture surfaces resulting from the adhesion test have been investigated and the fracture behavior has been characterized. A difference in fracture mechanism between the three heat treatments has been found. The two cyclic heat treatments give fracture in the top coat/bond coat interface while isothermal heat treatment gives fracture in the top coat.

  • 34.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Brodin, Håkan
    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.
    Östergren, Lars
    Volvo Aero Corporation, SE-46181 Trollhättan, Sweden.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, SE-61283 Finspång, Sweden.
    Influence of isothermal and cyclic heat treatments on the adhesion of plasma sprayed thermal barrier coatings2011In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 205, no 23-24, p. 5422-5429Article in journal (Refereed)
    Abstract [en]

    The adhesion of thermal barrier coatings (TBC) has been studied using the standard method described in ASTM C633, which makes use of a tensile test machine to measure the adhesion. The studied specimens consist of air plasma sprayed (APS) TBC deposited on disc-shaped substrate coupons of Ni-base alloy Hastelloy X. The bond coat (BC) is of a NiCoCrAlY type and the top coat (TC) consists of yttria–stabilised–zirconia. Before the adhesion test, the specimens were subjected to three different heat treatments: 1) isothermal oxidation at 1100 °C up to 290 h, 2) thermal cycling fatigue (TCF) at 1100 °C up to 300 cycles and 3) thermal shock at ~ 1140 °C BC/TC interface temperature up to 1150 cycles. The adhesion of the specimens is reported and accompanied by a microstructural study of the BC and the thermally grown oxides (TGO), as well as a discussion on the influence of BC/TC interfacial damage on adhesion properties of TBC. The adhesion was found to vary with heat treatment, as well as with heat treatment length.

  • 35.
    Eriksson, Robert
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Östergren, Lars
    Volvo Aero Corporation, Trollhättan.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    The Influence of Substate Material on the Thermal Cycling Fatigue Life of Thermal Barrier Coating Systems2012In: ECF19 Proceedings, 2012Conference paper (Refereed)
  • 36.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Östergren, Lars
    GKN Aerospace Engine Systems, Trollhättan.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Thermal Cycling Fatigue of Thermal Barrier Coatings- Rig and Experiment Design2014Conference paper (Refereed)
    Abstract [en]

    Ceramic thermal barrier coatings are used for thermal insulation in gas turbines to protect metallic components from high-temperature degradation. The ceramic coating may, due to its different coefficient of thermal expansion, crack and spall off the metallic component, thus rendering the component unprotected against high-temperature. Thermal cycling rigs of various designs are used to evaluate the durability of thermal barrier coatings. The present paper reports the result from a round robin test including three thermal cycling rigs at different locations. To better understand the influence of rig design on the thermal cyclic lives of thermal barrier coatings, some test parameters, such as the material of the specimen table and the cooling rate, were varied in one of the rigs. Furthermore, two different specimen geometries, rectangular and disc-shaped, were tested. The specimen table material was found to greatly influence the cooling rate of the specimens, more so than variations in the cooling airflow. The rectangular specimens were found to be more sensitive to test setup than the disc-shaped specimens; under certain conditions, the rectangular specimens could be made to fracture from the long side, rather than the short side of the specimen edge, which shortened the thermal cyclic life of the coatings.

  • 37.
    Eriksson, Robert
    et al.
    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.
    Brodin, Håkan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Östergren, Lars
    GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Influence of substrate material on the life of atmospheric plasmas prayed thermal barrier coatings2013In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 232, no 15, p. 795-803Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs) are used in gas turbines to prolong the life of the underlying substrates and to increase the efficiency of the turbines by enabling higher combustion temperatures. TBCs may fail during service due to thermal fatigue or through the formation of non-protective thermally grown oxides (TGOs). This study compares two atmospheric plasma sprayed (APS) TBC systems comprising of two identical TBCs deposited on two different substrates (Haynes 230 and Hastelloy X). The thermal fatigue life was found to differ between the two TBC systems. The interdiffusion of substrate elements into the coating was more pronounced in the TBC system with shorter life, however, very few of the substrate elements (only Mn and to some extent Fe) formed oxides in the bond coat/top coat interface. Fractography revealed no differences in the fracture behaviour of the TBCs; the fracture occurred, in both cases, to about 60% in the top coat close to the interface and the remainder in the interface. Nanoindentation revealed only small differences in mechanical properties between the TBC systems and a finite element crack growth analysis showed that such small differences did not cause any significant change in the crack driving force. The oxidation kinetics was found to be similar for both TBC systems for the formation of Al2O3 but differed for the kinetics of non-Al2O3 TGOs where the TBC system with shortest life had a faster formation of non-Al2O3 TGOs caused by a faster Al depletion. The difference in non-Al2O3 TGO growth kinetics was considered to be the main reason for the difference in life.

  • 38.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Östergren, Lars
    GKN Aerospace Engine Systems, Trollhättan.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Influence of Interface Roughness on the Fatigue Life of Thermal Barrier Coatings2013Conference paper (Refereed)
  • 39.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Brodin, Håkan
    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.
    Östergren, Lars
    GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    TBC bond coat-top coat interface roughness: influence on fatigue life and modelling aspects2013In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 236, p. 230-238Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the metallic bond coat. The life prediction of TBCs often involves finite element modelling of the stress field close to the bond coat/top coat interface and thus relies on accurate modelling of the interface. The present research studies the influence of bond coat/top coat interface roughness on the thermal fatigue life of plasma sprayed TBCs. By using different spraying parameters, specimens with varying interface roughness were obtained. During thermal cycling it was found that higher interface roughness promoted longer thermal fatigue life. The interfaces were characterised by roughness parameters, such as Ra, Rq and Rq, as well as by autocorrelation, material ratio curves, probability plots and slope distribution. The variation of spray parameters was found to affect amplitude parameters, such as Ra, but not spacing parameters, such as RSm. Three different interface geometries were tried for finite element crack growth simulation: cosine, ellipse and triangular shape. The cosine model was found to be an appropriate interface model and a procedure for obtaining the necessary parameters, amplitude and wavelength, was suggested. The positive effect of high roughness on life was suggested to be due to a shift from predominantly interface failure, for low roughness, to predominantly top coat failure, for high roughness.

  • 40.
    Hass, Ursula
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Health Care Analysis. Linköping University, Faculty of Health Sciences.
    Andersson, Agneta
    Linköping University, Department of Medical and Health Sciences, Social Medicine and Public Health Science. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in West Östergötland, Research & Development Unit in Local Health Care.
    Brodin, Håkan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Persson, Jan
    Linköping University, Department of Medical and Health Sciences, Division of Health Care Analysis. Linköping University, Faculty of Health Sciences.
    Assessment of computer-aided assistive technology: analysis of outcomes and costs1997In: Augmentative and Alternative Communication: AAC, ISSN 0743-4618, E-ISSN 1477-3848, Vol. 3, no 2, p. 125-135Article in journal (Refereed)
    Abstract [en]

    The objectives of this study were to identify and quantify outcomes related to implementation of computer-aided assistive technologies (CAAT) for individuals with communication disabilities and to analyze CAAT costs comprising the selected devices as well as the selection process. The study was designed as a pre/post, longitudinal study. Intermediate and global measures were used as outcome measures. Costs reflecting the resource consumption for the selected devices as well as the selection process were estimated. Individuals with communication disabilities who were referred to the regional CAAT centers were asked to participate in the study. Eighty-seven individuals were recruited. The study shows that usage of CAAT involves reasonable marginal costs for the selection process and equipment (on average SEK 14,800). Usage of CAAT diminishes disability and increases skills in handling computers. However, the outcomes are not entirely positive regarding handicap, health-related quality of life, and utility.

    Read More: http://informahealthcare.com/doi/abs/10.1080/07434619712331277928

  • 41.
    Jinnestrand, Magnus
    et al.
    Linköping University, Department of Mechanical Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Brodin, Håkan
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Crack initiation and propagation in air plasma sprayed thermal barrier coatings, testing and mathematical modelling of low cycle fatigue behaviour2004In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 379, no 1-2, p. 45-57Article in journal (Refereed)
    Abstract [en]

    In the present paper failure mechanisms in air plasma sprayed thermal barrier coatings for land-based gas turbines have been studied. This has been done by finite element simulations and fractographic investigations of low cycle fatigue (LCF) tested material, here chosen as an 350 μm thick partially stabilised zirconia top coat (TC) together with a 150 μm thick Ni-Co-Cr-Al-Y bond coat (BC) on a nickel base substrate (Haynes 230). Both LCF testing, modelling results and fractographic investigations point in the same direction. An increased thickness of the thermally grown oxide (TGO) does decrease the LCF life of a coated structural alloy. Several points of crack initiation were found, in the TGO at the TC/BC interface, at the oxide network within the BC and at oxide inclusions between BC and substrate. During LCF tests the initiated cracks will grow radially into the substrate material. The behaviour is explained by increased TC/BC delamination stresses and changed oxidation behaviour with increased oxidation times.

  • 42.
    Li, Xin-Hai
    et al.
    Siemens Industrial Turbomachinery AB, Finspång.
    Heinze, Sebastian
    Siemens Industrial Turbomachinery AB, Finspång.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Eriksson, Robert
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Studies of Air Plasma Sprayed Thermal Barrier Coatings and Their Surface Roughness for Applications in Siemens Medium Size Gas Turbines2012Conference paper (Refereed)
  • 43.
    Moverare, Johan
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Leijon, Gunnar
    SWEREA Kimab AB, Stockholm, Sweden.
    Brodin, Håkan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Palmert, Frans
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Effect of SO2 and water vapour on the low-cycle fatigue properties of nickel-base superalloys at elevated temperature2013In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 564, p. 107-115Article in journal (Refereed)
    Abstract [en]

    In this study the effect of SO2+water vapour on strain controlled low cycle fatigue resistance of three different nickel based superalloys has been studied at 450 °C and 550 °C. A negative effect was found on both the crack initiation and crack propagation process. The effect increases with increasing temperature and is likely to be influenced by both the chemical composition and the grain size of the material. In general the negative effect decreases with decreasing strain range even if this means that the total exposure time increases. This is explained by the importance of the protective oxide scale on the specimen surface, which is more likely to crack when the strain range increases. When the oxide scale cracks, preferably at the grain boundaries, oxidation can proceed into the material, causing preferable crack initiation sites and reduced fatigue resistance.

  • 44.
    Sadrossadat, Mohsen
    et al.
    Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology.
    Brodin, Håkan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology.
    Experimental realization and finite element simulation of residual stresses in Al-Si water sprayed cast componentsManuscript (preprint) (Other academic)
    Abstract [en]

    In this study, experiments were carried out to develop insights into  and understanding of the residual stresses that can arise during different thermal treatments of Al-Si components. The study consisted of two steps: experimental measurement of the residual stresses accumulated in the components and simulation of the results by finite element analysis. A special cooling apparatus was designed and built in order to perform selective cooling of the component. In the simulation step, the tensile behavior and parameters such as Young’s modulus values determined by tensile tests at different temperatures and the recorded cooling curves in the first step were used as input for the Abaqus software. The experimental results obtained by thermal analysis and residual stress measurement showed that by choosing a specific holding temperature before quenching, the value of residual stress increases linearly with flow rate of water spray coolant. On the other hand, for a constant value of cooling water flow rate, the maximum temperature difference between the middle and side bars of the test specimen (ΔTmax) and residual stress level decrease when the value of starting temperature of cooling decreases. It was shown that the strain gage method and thermal analysis are reliable techniques for measuring thermal residual stresses and prediction of residual strains in Al-Si components, respectively. It was also shown that the results obtained by simulation are reasonably in acceptable agreement with the experimentally measurements.

  • 45.
    Sjöström, Sören
    et al.
    Siemens Industrial Turbomachinery AB, FINSPÅNG, Sweden.
    Brodin, Håkan
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Thermomechanical fatigue life of TBCs - experimental and modelling aspects: 2010In: Advanced Ceramic Coatings and Interfaces V: Ceramic Engineering and Science Proceedings, Volume 31 / [ed] Zhu D, Lin H-T, Westerville, OH, United States: American Ceramic Society Inc. , 2010, Vol. 31, p. 23-39Conference paper (Refereed)
    Abstract [en]

    The fatigue life of APS TBC under TMF loading has been studied. Failure can be by spallation from convex surfaces, spallation from flat or nearly flat surfaces and spallation from sharp edges. The damage evolution leading to final failure has been studied experimentally, and based on the experimental observations, a fracture-mechanical model for the formation and growth of cracks in or near the thermally grown oxide and for the final failure of the TBC has been set up.

  • 46.
    Sjöström, Sören
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Jinnestrand, Magnus
    Siemens Industrial Turbomachinery AB, Finspång.
    Thermomechaical Fatigue Life of a TBC - Comparison of Computed and Measured Behaviour of Delamination Cracks2013Conference paper (Refereed)
1 - 46 of 46
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