| 1. |
- Andersson, K., et al.
(författare)
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Failure Investigation of an Airline Engine Failure During Take Off
- 2013
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Ingår i: Praktische Metallographie/Practical Metallography. - : Walter de Gruyter GmbH. - 0032-678X. ; 50:12, s. 821-830
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Tidskriftsartikel (refereegranskat)abstract
- An Iran Airlines CF6-8002A2F engine had a turbine failure during takeoff from the Arlanda airport in Sweden, in January 2010. Failure investigation of the engine was performed by Lufthansa Technik AG (LHT). The Swedish Accident Investigation Board (SHK) requested a second opinion of the available High Pressure Turbine (HPT) Diffuser Aft Seal hardware, received from LHT, and because of GKN Aerospace Sweden's extensive experience as Original Equipment Manufacturer (OEM) of Swedish fighter engines this second failure analysis work was performed by GKN. The failure investigation of the Diffuser Aft Seal pieces and fragments received from LHT revealed no fractures or fatigue cracks which are believed to be evidences of the primary cause to the failure. However, a secondary fatigue crack was found in an aft tooth fragment from the Diffuser Aft Seal. This tooth fragment has also a machining step on the forward surface, between a repair weld and the original tooth, with a geometry which gives a stress concentration factor of about 2.5 for radial and bending stresses in this area. This machining step may have contributed to initiate a fatigue crack in the seal tooth.
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| 2. |
- Andersson, Thorvald, 1946, et al.
(författare)
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Preparation and characterization of the ITO surface and the Al/Alq3/ITO heterostructure for OLEDs
- 2007
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Ingår i: Materials Science and Engineering B. ; 145, s. 48-56
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Tidskriftsartikel (refereegranskat)abstract
- We have made a detailed investigation of structure and chemical composition in thermally grown Al/Alq3/ITO layer structures intended for light emission. The different parts of the structure were studied by X-ray photoelectron spectroscopy and microscopical techniques. The indium tinoxide substrate surface consisted of grains 20–50 nm in diameter and about 5 nm in height, which also showed molecular sized sub-grain features. Due to the ambient the ITO surface was covered by a 1 nm thick hydrocarbon layer which serves as the actual surface on which an organic layer is deposited for device fabrication. A structural model for the indium tin oxide surface, on which the small molecules were deposited, was suggested. The substrate surface was treated to study the relation between the surface manipulation and the hole injection barrier. Such surface modification significantly improved the performance of a single layer Alq3 organic light emitting diode. Depth profiling of the complete structure, revealed that the aluminium contact mostly consisted of aluminium oxide with some intermixing of carbon. Further, variations of the atomic concentration of the elements In, Sn, C and O and a minor shift in their binding energies were measured. Both, position and shape of the oxygen and indium peaks were changed during argon ion sputtering. At the Alq3/ITO interface an indium–oxygen compound, different from that on the original surface, hadformed. Various effects of the compositional findings on the light emission are discussed.
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| 3. |
- Baiamonte, Lidia, et al.
(författare)
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Carbide-laden coatings deposited using a hand-held high-velocity air-fuel (HVAF) spray gun
- 2021
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 406
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Tidskriftsartikel (refereegranskat)abstract
- Driven by sustainability and cost considerations, there is growing interest in power generation utilizing renewable sources, especially biomass and waste. While premature degradation of power plant components due to corrosion is well-known, erosion can be a dominant damage mechanism in plants that use “pure” biomass with less corrosive elements like Cl, K, etc. Circulating fluidized bed (CFB) parts are prone to erosion-driven damage and demand periodic re-protection or replacement. In response to the above, this preliminary study evaluates a selection of complex carbide-based coatings to enhance protection against erosion to prolong service life of boiler components. Recognizing on-site coating requirements of real boiler applications, a specific focus is on evaluating performance of a hand-held high-velocity air-fuel (HVAF) spray gun and compare it with the current state-of-the-art high-velocity oxy-fuel (HVOF) deposition. Coatings developed by the above routes have been characterized with microstructural analyses, and their performance evaluated and ranked in an air-jet erosion rig at various impact angles.
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| 4. |
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| 5. |
- Battabyal, Manjusha, 1979, et al.
(författare)
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Comparison of microstructure in Ni-Al single splats and millimeter sized drops
- 2011
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Ingår i: Surface Modification Technologies XXV. - 9788191057140 ; , s. 3-12
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Konferensbidrag (refereegranskat)abstract
- Splat studies are a central area of research because they can provide fundamental knowledge on the phenomena controlling the final coating properties such as coating microstructure and adhesion. Wetting and heat transfer are expected to influence the final splat shape while they are in turn controlled by the presence of oxides and adsorbed species on the substrate surface. It is however difficult to follow the flattening of a sprayed droplet at the micrometer scale. Since the mid nineties, so-called free falling experiments have been developed with which it is possible to simulate the thermal spray process. The millimetre sized drops allow investigating the flattening and solidification occurring in milliseconds instead of in microseconds.In this study, the microstructure of plasma sprayed Ni-Al splats and millimetre sized droplets produced on TiAlV and pure Ti substrates, respectively, are compared. By use of scanning electron microscopy (SEM), especially the cross-section of splats and droplets has been investigated. In the splats, diffusion across the splat-substrate interface and the formation of an interface layer is detected. In the droplets, up to 3 different layers are formed at the interface to the substrate. The microstructure at the interface and the phases present are discussed and their influence on heat transfer and coating properties are described.In this study, the microstructure of plasma sprayed Ni-Al splats and millimetre sized droplets produced on TiAlV and pure Ti substrates, respectively, are compared. By use of scanning electron microscopy (SEM), especially the cross-section of splats and droplets has been investigated. In the splats, diffusion across the splat-substrate interface and the formation of an interface layer is detected. In the droplets, up to 3 different layers are formed at the interface to the substrate. The microstructure at the interface and the phases present are discussed and their influence on heat transfer and coating properties are described.
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| 6. |
- Björkeborn, Karin, 1978, et al.
(författare)
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Effects on machining due to microstructure variations in a case hardening steel
- 2008
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Ingår i: Proceedings of the Swedish Production Symposium - 2008.
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Konferensbidrag (refereegranskat)abstract
- In manufacturing industry, variations in machinability are regularly observed when producing the same part out of different material batches of a case hardening steel. However, material batches showing a decreased machinability often have properties within the material specification. Thus, for an increased machinability and a more robust production of case hardening steel parts, the relationship between microstructure and machinability needs to be further investigated. In this study, machinability has been evaluated for a specific case hardening steel with respect to pearlite nodular size, phase distribution and interlamellar spacing of pearlite. These variations in microstructure have been achieved by altering the annealing cycle, i.e. austenitizing temperature, holding time and temperature for pearlite formation. The criterions for machinability which are taken into consideration in this investigation are tool wear and chip formation. Furthermore, a comparison of cutting forces and surface integrity for the tested microstructures will be presented. The results from tests show a difference between material with larger pearlite nodules and a material with smaller pearlite nodules. For tool wear, the material with larger pearlite nodules has a decreased machinability. However, for chip formation the result is opposite, and a material with larger pearlite nodules has an increased machinability.
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| 7. |
- Björkeborn, Karin, 1978, et al.
(författare)
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Ranking of materials by their machinability applying a short term test
- 2008
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Ingår i: Proceedings of 2nd International Conference on Innovative Cutting Processes and Smart Machining (INTERCUT 2008), Cluny, France.
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Konferensbidrag (refereegranskat)abstract
- For case hardening steel, the relationship between microstructure and machinability is investigated. To be able to determine the influence of morphology, i.e. grain size, phase distribution and interlamellar spacing in pearlite, homogeneous material is required. However, a homogeneous microstructure can only be guaranteed when small material volumes are used. For that reason the Volvo Standard Machinability Test has been applied, as it allows ranking of materials with respect to their machinability by removing only small amounts of material (~800 mm of a bar with 50 mm diameter for each material). In addition to what is described in the standard of the test, a number of observations and experiences have been made. In this article the observations in connection with the Volvo Standard Machinability Test are critically discussed. Furthermore, the results of the machinability test of the case hardening steels are presented.
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| 8. |
- Björkeborn, Karin, 1978, et al.
(författare)
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Study of machinability of case hardening steel in production environment
- 2009
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Ingår i: Proceedings of the Swedish Production Symposium - 2009.
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Konferensbidrag (refereegranskat)abstract
- The investigation is based on field studies in full scale production and machinability is evaluated in terms of tool wear of cemented carbide inserts. The aim of this study was to investigate how rather small variations in chemical composition between different batches of a case hardening steel affect machinability. Continuous wear is observed to be low for all of the investigated inserts. However, some of the tools show discontinuous wear, like spalling of coating. The discontinuous wear is believed to be caused by unevenness of the forged scale of the machined component and not by variations in the material workpiece bulk properties. Since this wear mechanism may cause a premature tool breakage, it is very important to investigate this finding in more detail. To be able to evaluate the effect of chemical composition on machinability further experiments are necessary, in a more controlled environment with a material having a larger variation in composition.
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| 9. |
- Björkeborn, Karin, 1978, et al.
(författare)
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Study of microstructural influences on machinability of case hardening steel
- 2010
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Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 49:5-8, s. 441-446
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Tidskriftsartikel (refereegranskat)abstract
- The overall aim of this study is to establish knowledge about how the material specificationof case hardening steel should be modified in order to create a robust and predictable productionprocess with focus on machinability. In this study, emphasis is laid on studying microstructurevariations produced by changing holding time and temperature in the annealing process. Astandardized milling test was used to assess machinability (with respect to tool wear) as this methodhas the advantage of only needing small diametrical samples and low material volumes. From theresults of the test, it can be concluded that machinability is more influenced by pearlite nodular sizethan by pearlite morphology. Furthermore, it can be stated that hardness is not a suitable criterion fordetermining machinability of case hardening steel. In the manufacturing process of transmission parts(such as gear milling/hobbing) high speed steel tools are commonly used. The same type of tool isapplied in the standardized milling test. However, the obtained ranking (of machinability) for thedifferent materials is also applicable if other types of cutting tools are used.
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| 10. |
- Bouwhuis, Brandon, et al.
(författare)
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Microstructure in work-hardened micro-truss materials given post-forming annealing treatments
- 2010
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Ingår i: Proceedings of 2010 TMS Annual Meeting. ; CD
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Konferensbidrag (refereegranskat)abstract
- Micro-truss cellular materials can be used as structurally efficient cores in light-weight sandwich panels. These sandwich cores have been produced using deformation-forming approaches, which introduce plastic strain into the truss struts. While this imparted strain can be used to strengthen the overall micro-truss core, it also drives recrystallization and grain growth if sandwich panel assembly involves conventional brazing treatments that subject the truss core to elevated temperatures. In addition to losing a potential strengthening mechanism, brazing can also result in the grain size of the annealed microstructure approaching the cross-sectional dimensions of the micro-truss struts. The present study is an examination of the strut microstructures in aluminum alloy and stainless steel micro-truss materials fabricated using a deformation-forming approach, and following a post-fabrication annealing step. These results serve as a guideline for future sandwich panel thermal processing to minimize the reduction of strength due to annealing and detrimental size effects.
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