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  • 1.
    Adeva Rodil, Teresa
    Karlstad University, Division for Engineering Sciences, Physics and Mathematics.
    Edge effect on abrasive wear mechanisms and wear resistance in WC-6wt.% Co hardmetals2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    Wear of hardmetals is a complicated topic because the wear resistance and the wear mechanisms are influenced by microstructural factors. Although edge wear resistance has a vital importance, most of the researches made in laboratories are related to flat wear resistance using coarse abrasive paper. This situation produces problems with the prediction of abrasive wear behaviour and with the estimation of the lifetime of cutting edges of different kinds of tooling.

    Several studies have been done in order to clarify edge wear behaviour. It has been published correlations of the edge toughness to the load and to the bulk fracture toughness. In those publications coarse abrasive or Vickers indenter were used.

    In the present research, edge shaped specimens of WC-6wt%Co grades were investigated. In order to compare the obtained results for flat sliding and edge wear behaviour two test arrangements, pin on flat disc and edge on flat disc were employed. The specimens were tested using 120, 320, 800 and 2400 mesh SiC abrasive paper and the worn surfaces were investigated using SEM instrument to evaluate wear mechanisms. The edge wear was observed was discussed in relation to wear mechanisms investigated and correlated to the flat wear behaviour.

    The obtained results showed limited applicability of the results obtained with the pin on the flat disc test arrangement for prediction of the edge wear resistance, especially in the case when size of the abrasive particles is close to the WC grain size. However, both edge and flat wear results were similar in; 1) large WC grain sized hard metals wore more than fine grain sized against coarse abrasive paper whereas the reverse occurred against fine abrasives, and 2) wear mechanisms were mainly ploughing (or grooving) for fine grain sized hardmetals in all cases, whereas wear mechanisms changed from ploughing to binder removal and carbide pull-out going from coarse to fine abrasive paper.

  • 2.
    Andersson, Stefan
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Analysis of welding in comparable steel grades: Influence of steel grade on the welding process2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis is written to examine the influence of different low carbon steel sheet materials on the GMAW welding process. During welding the properties of the base material influence the productivity of the welding process. The purpose of this thesis is to examine how the choice of material and welding speed affect the welding process and the productivity.

    A literature survey was performed to describe the welding technique and the differences in manufacturing for the sheet materials as well as the effect of alloying and welding on the sheet material. Defects in the weld and methods used to determine them are explained. Test pieces of the different sheet materials were welded with the GMAW process and examined.

    The result shows that there is a variation in the welding process regarding weld penetration. Measurements also show that welding speed and gap have little influence on the hardness of the weld and heat-affected zone and that the S355MC is more likely to suffer from a narrower toe transition radius than S355NL and S355MC Si. This and the higher area in the Y2 region for the S355MC could indicate a stronger inward flow in the weld pool during welding possibly a result of surface active agents such as oxygen and sulphur.

  • 3.
    Buck, Dietrich
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Massivträ: Jämförelse mellan olika principer för sammanfogning av trä till plattelement med avseende på pris, hållfasthet och ekologi2014Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The increasing use of solid wood construction methods can have a positive impact on the sustainability of constructions. The development of computer-controlled processing techniques enables the solid wood timber industry to rationalize the construction of buildings. The solid wood techniques come at time and will be higher valued in the future due to the natural characteristics of this material.

    The improvement of solid wood methods has resulted in various techniques to join wood into solid prefabricated parts. There is a need for a comparative market study of the different principles of solid wood construction to widen the knowledge and to explain interested builders the viability of these techniques. The key question for this study is: Which techniques of combining solid wood elements to whole boards are the most favorable ones concerning wood construction buildings – leaving apart questions of production costs, durability and ecological considerations?

    To point out the utility of these construction techniques and give them a broader understanding a general study of solid wood construction has been presented. The comparative study is based as well on studies of literature as on reviews of 27 companies in 6 countries.

    The following techniques for the production of boards made of solid timber elements are considered in this report:

     Laminating

     Nailing

     Stapling

     Screwing

     Stress laminating

     Doweling: vertically, horizontally, diagonally and with wooden screws

     Dovetailing techniques

     Wood welding techniques

    The study shows that the techniques of solid wood construction are very different in itself. CLT of cross-laminated timber scores highest in terms of cost and durability, but if one considers ecological factors, dovetailing is best. Taking into account both durability and ecological considerations, doweling is best. These alternatives give some freedom of choice regarding the visibility of surfaces and the efficient use of lower qualities of timber and they are therefore suitable for residential construction buildings.

    CLT is the most cost-effective, not patented and well established option in the market; the development of more health-friendly adhesives is still going on. Current researches demonstrate an alternative: Wood welding joins the parts better together than gluing them.

    Considered from the ecological viewpoint, boards made exclusively of wood, are preferable since no chemicals or not renewable resources are used. Recent researches show, that solid wood constructions have positive effects on the health of the residents of these buildings in comparison of buildings using non-natural materials.

  • 4.
    Domare, Emma
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Generating gear grinding: An analysis of gringing parameters's effect on gear tooth quality2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Generating gear grinding is a method used for hard machining of gearbox gears. It facilitates a productive gear manufacturing with tight tolerances regarding surface roughness and geometrical accuracy. However, if the grinding is done with incorrect parameters, so called grinding burns can arise with consequences such as changes in surface hardness, changes in residual stress levels, surface embrittlement and compromised fatigue strength. This thesis investigates the gear tooth quality resulting from grinding parameters contributing to an improved grinding time. A literature study will cover gear geometries and material, grinding wheel properties, influences by grinding parameters and several verification methods. An experimental test will then be used to put four different grinding parameters to the test. The results showed that an increased cutting speed indicated finer surface roughness andincreased Barkhausen noise but showed no influence on gear geometry. Increasing both rough and fine feed rates resulted in a minor increase in geometry deviation but no significant difference in surface roughness. Large variations within the different verification method results related to grinding burns madeit difficult to draw conclusions regarding the experimental factors chosen. However, several factors apart from the experimental ones varied in the testing were believed to have significant influence, such as the flow of the cooling fluidand the amount of retained austenite from the carburizing process. In fact, the trends which seemed to be connected to these factors could be seen in both Barkhausen noise analysis, hardness measurementsand microstructure.

  • 5. Epure, Alexandru
    Maskinduglighet på planlaserskärare2008Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [sv]

    Lars Höglund AB is one of Scandinavia’s most qualified manufacturers of sheet metal products and provides custom designed products of very detailed precision. One of the main methods of manufacturing is laser cutting. When Lars Höglund AB signed up a new customer, with high demands in tolerances for the products, Lars Höglund AB thought it would be necessary to know the capability of the laser cutting machine. Also the process of how to retrieve this capability was interesting.

     

    The capability will be researched for the following elements:

     

    • Cutting right angles in squares with a corner radius of 1 mm
    • Cutting corners which are not right angle
    • Cutting of circles with constant radius

     

    Measurements were made on 150 pieces of sheet metal details, which had been cut out by the machine.  The data from the measurements where later used to study the capability. The capability study includes such things as calculations of capability indexes Cp and Cpk, the calculations are based on histograms and lean-mean-curves, constructed from the measurement data. The capability of the laser cutting machine was high except for some elements. Those elements with minor capability were the cutting of corner two and three for the rectangles which had a smaller radius than expected, side X for the triangles which were too long and also the diameter of the circles were too big. Advices on how to correct the faults have been given if Lars Höglund AB wants to further more improve the capability of the machine.

  • 6.
    Eriksson, Mats
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Sliding wear performance of electroplated hard chromium and autocatalytic nickel-phosphorus coatings at elevated temperatures2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis was written for a Swedish valve manufacturer to find out in what temperature regimes it was possible to replace electroplated hard chromium with autocatalytic electroless nickel-phosphorus. In this work the dry sliding wear properties of electroplated hard chromium and autocatalytic electroless nickel-phosphorus(10% P) were compared. All tests and investigations were done by using available equipment at Karlstads University. The tests were made to find out how the wear of these coatings behaved at different temperatures, how different substrates influence the wear of these coatings and how the roughness of the substrate surface influence the wear properties of these coatings.

    The method used for the wear tests was block-on-ring with a counterformal contact mode. The tests were executed in room temperature, 300C and 400C; with a normal load of 100N, sliding speed was 150rpm and duration of the tests were 15 minutes. All tests were done in an argon gas atmosphere. The coatings was deposited onto the cylinders with a thickness of 30µm. The different substrates used were an austenitic stainless steel(1.4404) and an austenitic-ferritic(duplex) stainless steel(1.4460). Half of the austenitic cylinders had a machined surface and all the others(including duplex cylinders) were machined and grinded to achieve a smoother surface. The blocks used as countersurface were made out of austenitic-ferritic(duplex) stainless steel(1.4460).

    Equipment used to investigate the wear tracks were stereo microscopy, profilometer, microhardness tester and scanning electron microscopy(SEM). The coatings were investigated in matter such as wear depth, wear mode, wear mechanism, chemical composition, topography, morphology, cross-section and hardness.

    The results of this work showed that the nickel coating wear tracks maximal depth were less deep than those of hard chrome, at room temperature. At elevated temperatures the performance varies. The coatings deposited onto cylinders made out of duplex stainless steel performed better than those deposited onto austenitic cylinders. The nickel coating performed better deposited onto the substrates with smooth surface and the chrome coating performed better deposited onto the substrates with rough surface

  • 7.
    Gåård, Anders
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Sarih, Rahim M.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Influence of Tool Material and Surface Roughness on Galling Resistance in Sliding Against Austenitic Stainless Steel2012In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 46, no 2, p. 179-185Article in journal (Refereed)
    Abstract [en]

    Transfer and accumulation of adhered sheet material, generally referred to as galling, is a major cause for tool failure in sheet metal forming. In the present work, the galling resistance of three different tool materials was evaluated in lubricated sliding against austenitic stainless steel using a SOFS tribometer. All tool materials were prepared to four different surface roughnesses, ranging from a polished surface with R (a) = 0.05 mu m to a ground surface with R (a) = 0.3 mu m. The overall best performance was obtained for polished nitrogen alloyed powder metallurgy (PM) tool steel, where galling was detected only at the highest load evaluated, 700 N. However, for both the D2 type tool steel and nodular iron, best performance was observed for the surface possessing a surface roughness of 0.1 mu m. The improved galling resistance for the rougher surfaces was related to filling of grinding scratches with sheet material during the initial stage of sliding, prolonging the development of protruding sheet material on the tools surface. Similar trend was not observed for the PM steel, which was related to width of the scratches originating from the surface preparation, in relation to tool microstructure.

  • 8.
    Jonhed, Anna
    Karlstad University, Faculty of Technology and Science.
    Properties of modified starches and their use in the surface treatment of paper2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The papermaking industry uses a large amount of starch each year, both as a wet-end additive and as a rheological modifier in surface sizing and coating colors. It is important to be able to reduce the amount of chemicals used in the papermaking and surface treatment process, to reduce costs and to make the process even more efficient. Interest in new high-performance starches is great. By using these new types of starches, improved recycling of barrier products may be obtained as well as a reduction in the use of synthetic sizing agents. The objectives of this work were to understand the behavior of temperature-responsive hydrophobically modified starches, where the solubility in water simply can be adjusted by temperature or by polymer charge, to improve the barrier properties, like the water vapor permeability, mechanical properties and water resistance (Cobb and contact angle) of papers surface sized by starch-containing solutions, and to investigate the potential for industrial use of these temperature-responsive starches. It was demonstrated that the temperature-responsive starches phase separate upon cooling and, depending on the charge density of the starch, a particulate precipitation or a gel-like structure was obtained. The starch with zero net charge showed a larger increase in turbidity than the starch with a cationic net charge, indicating that particulate precipitation is favored by a zero net charge and that the formation of a gel network is favored by charged starch molecules. Further, the starches formed inclusion complexes with surfactants, giving stabilization to the starches in the presence of surfactants. The net charge density of the starch and the charge of the surfactant determined whether or not an inclusion complex would form between them. Important mechanisms for the stability of the starch seemed to be formation of mixed micellar-like structures between the hydrophobic chain of the starch and the surfactant along the starch backbone in addition to formation of inclusion complexes between the starch and the surfactant. The hydrophobically modified starches showed higher hydrophobic surface character when applied to the paper surface above the critical phase separation temperature than with application at room temperature. Free films of the temperature-responsive starches showed good barrier against oxygen, but no barrier against water vapor. The mechanical properties decreased with addition of glycerol to the films.

  • 9.
    Jonsson, Jonathan
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Different coatings effect on tool-life when milling hardened tool steels2015Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Abstract

    This thesis work is about finding out which coating should be used for which hardened tool steel and this was done by testing different coated cutting tools in different kinds of tool steels. The thesis work is performed at Uddeholms AB together with Uddeholms AB in the department of R&D at machinability cooperating with eifeler-Vacotec GmbH. The thesis work is going on from the end of January to the start of June and is a part of the education as mechanical engineer at Karlstad University and includes a total of 22,5 hp. The objective after finished thesis work is to be able to leave a recommendation to Uddeholms AB which coating is most suitable for each tool steel. To be able to leave that recommendation cutting tests are performed in four different hardened steel grades from Uddeholms AB combined with seven different coatings from eifeler-Vacotec GmbH. Steel grades tested are NIMAX®, DIEVAR®, VANADIS® 10 and ORVAR® SUPREME and coatings tested are CROSAL®, EXXTRAL® and SISTRAL® in different compounds. ORVAR® SUPREME gave such a long cutting tool-life that it was left for further investigation due to time limits that the thesis work had. In the other three tool steels it was possible to get a recommendation out of the four coatings tested in each tool steel. The coating that is recommended for each tool steel is only based on the cutting tool lasting the longest in each tool steel. That is not how a recommendation usually is formed, however for this thesis work there is no time for checking all the aspects that is vital for a proper recommendation. In order to get a proper recommendation, further more aspects that are checked are for example:

    • Different cutting parameters (cutting speed, feed, etc.)
    • Different geometries on the cutting tool
    • Smoothness of the cutting tool and the coating

    In table 1 there is a compilation of which coating that was recommended for which tool steel.

    Table 1. This is a compilation of which coating that was recommended for which tool steel.

    NIMAX®               CROSAL® V1

    DIEVAR®             SISTRAL® Ultrafine

    VANADIS® 10    SISTRAL® S

  • 10.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics, Science, Mathematics and Engineering Education Research.
    Microstructure and phase constitution of Ti-SiC coatings fabricated by selective laser melting2013Conference paper (Refereed)
  • 11.
    Krakhmalev, Pavel
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsava, Inna
    Central University of Technology, Free State, South Africa.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsev, Igor
    Central University of Technology, Free State, South Africa.
    Microstructural and thermal stability of selective laser melted 316L stainless steel single tracks2017In: South African Journal of Industrial Engineering, ISSN 1012-277X, E-ISSN 2224-7890, Vol. 28, no 1, p. 12-19Article in journal (Refereed)
    Abstract [en]

    To remove residual stresses, an as-built SLM object is usually posttreated. This treatment can affect the microstructure, changing the final mechanical characteristics. This investigation is focused on the microstructural characterisation of 316L austenitic stainless steel in as-built and annealed conditions. The SLM microstructure was relatively stable up to 900°C, when cell boundaries start to disappear. At higher temperatures, an insignificant grain coarsening was detected. These microstructural changes caused a gradual drop in the hardness. The obtained result is background for the future development of post-treatment regimens to achieve a high level in the final mechanical properties of SLM objects.

  • 12.
    Krakhmalev, Pavel
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Yadroitsev, I.
    Univ Lyon, Ecole Natl Ingn St Etienne ENISE, DIPI Lab, F-42023 St Etienne, France..
    Microstructure and properties of intermetallic composite coatings fabricated by selective laser melting of Ti-SiC powder mixtures2014In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 46, p. 147-155Article in journal (Refereed)
    Abstract [en]

    Transition metal silicides and carbides are attractive advanced materials possessing unique combinations of physical and mechanical properties. However, conventional synthesis of bulk intermetallics is a challenging task because of their high melting point. In the present research, titanium carbides and silicides composites were fabricated on the titanium substrate by a selective laser melting (SLM) of Ti -(20,30,40 wt.%)SiC powder mixtures by an Ytterbium fiber laser with 1.075 mu m wavelength, operating at 50 W power, with the laser scanning speed of 120 mm/s. Phase analysis of the fabricated coatings showed that the initial powders remelted and new multiphase structures containing TiCx, Ti5Si3C5, TiSi2 and SIC phases in situ formed. Investigation of the microstructure revealed two main types of inhomogeneities in the composites, (i) SiC particles at the interlayer interfaces and, (ii) chemical segregation of the elements in the central areas of the tracks. It was suggested and experimentally proven that an increase in laser power to 80 W was an efficient way to improve the laser penetration depth and the mass transport in the liquid phase, and therefore, to fabricate more homogeneous composite. The SLM Ti (20,30,40 wt.%)SiC composites demonstrated high hardness (11-17 GPa) and high abrasive wear resistance (3.99 x 10(-7)-9.51 x 10(-7) g/Nm) properties, promising for the applications involving abrasive wear. (C) 2013 Elsevier Ltd. All rights reserved.

  • 13.
    Nöbauer, Henrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    En utvärdering av metoder för att bestämma den förhöjda arbetstemperaturen vid svetsning av S355J22015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    One of the most common causes of failure in welded carbon steel constructions can be traced to small cracks that occur in the weld metal or in the area of the base metal that has been affected structurally by the energy from the welding process, also known as HAZ. These cracks can occur hours or days after the welding is completed and do so due to a combination of hydrogen that has penetrated the metal during the weld process, a hard and brittle microstructure and tensile stresses acting on the weld.

    A method to avoid these cracks is to preheat the material before welding. The increased temperature results in a slower cooling which reduces the risk of a martensitic microstructure and allow hydrogen to diffuse out of the most critical zones of the welded joint.

    There are many different methods for calculating the preheat temperature needed to counter these cracks. Most of them are solved graphically but attempts have been made to translate them into mathematical algorithms to facilitate calculations. The outcome of the methods may vary and different methods can be considered to be best applied to various steel. The purpose of this study is to investigate which method is best suited to determine the preheat temperature to eliminate the risk of hydrogen cracking for the structural steel S355J2.

    The methods used in this study was the mathematical CET, the graphic CEIIW and CEN and mathematical interpretations of the latter two. The evaluation was made by welding samples of plates with a thickness of 30 mm and with an incrementally increased preheat temperature. These samples were then subjected to both non-destructive and destructive testing to examine how prone they were to crack. An analysis of the weld microstructure was also conducted to identify the most critical zones.

    It turned out that the mathematical interpretations of the graphic methods differed so much from their graphical equivalent that they can not be recommended for use.

    It was also found that none of the original methods can be said to be best suited for S355J2 but the choice depended entirely on the heat input. For a heat input over 1.6 kJ/mm it is recommended to use the CET-method which estimated a temperature that gave good material parameters. For a heat input below 0.9 kJ/mm no method calculates a sufficiently high temperature, but the CEIIW-method is calculating the highest temperature and is therefore recommended for use. However, one should keep in mind that it was not sufficient and should therefore be seen as a conservative recommendation.

    No samples were welded between 0.9 kJ/mm and 1.6 kJ/mm but the recommendation is to use the CET- method because it is simple and calculates the maximum temperature.

    It was also found that the coarse grain zone was the area where hydrogen cracking is most likely to occur. 

  • 14.
    Pavlopoulou, E.
    et al.
    University Bordeaux, France.
    Fleury, G.
    University Bordeaux, France.
    Deribew, Dargie
    University Bordeaux, France.
    Cousin, F.
    CEA Saclay, France.
    Geoghegan, M.
    University Sheffield, England.
    Hadziioannou, G.
    University Bordeaux, France.
    Phase separation-driven stratification in conventional and inverted P3HT:PCBM organic solar cells2013In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 14, no 5, p. 1249-1254Article in journal (Refereed)
    Abstract [en]

    We have used neutron reflectivity to investigate the stratification of poly(3-hexylthiophene) (P3HT) and phenyl-C-61-butyric acid methyl ester (PCBM) blend films. Films were spun-cast on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) and titanium oxide (TiOx) layers to mimic the procedures followed for the fabrication of conventional and inverted organic photovoltaics respectively. The resultant scattering length density profiles reveal a PCBM-rich layer is formed in the vicinity of PEDOT: PSS or TiOx, while PCBM is depleted at the free surface of the film. PCBM segregation close to the substrate is further enhanced by annealing. This stratification is considered to be favorable only for inverted devices. (C) 2013 Elsevier B. V. All rights reserved.

  • 15.
    Rashid, Lezan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Overlay welding of FeCrAl alloys2016Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
    Abstract [en]

    In this master thesis different overlay welding methods suitable for boiler application has been investigated.

    The purpose of this project is to define advantages and disadvantages for each overlay welding methods and suggest some evaluation criteria on some commercial and experimental alloys aimed for overlay welding material.

    Many components in a boiler are made of low alloy steel and the atmosphere in the furnace region can be very complex; therefore many different types of corrosion can occur. Weld overlay is a process where one or multiple layers of corrosion resistant material are applied to a base material.

    The two overlay welding methods investigated in this study were Tungsten Inert Gas welding and Metal Inert/Active Gas welding. Tests were performed with FeCrAl alloys (Kanthal A, Kanthal D and some experimental alloys). FeCrAl alloys in general are ferritic iron-based steels with a typical concentration of 20-23 wt. % chromium and ~5 wt.% aluminum.

    Different overlay welding evaluation was made; visual examination, dye penetrant inspection, macro/micro examination, side bend test and short term corrosion test (~50hours).

    Conclusion of this thesis is that MIG welding is a more productive method than TIG, but more defects such cracks and lack of fusion can be produced for MIG welding. These defects can be “fixed” if welding parameters is optimized. If repairing a certain place TIG welding is a better option. A conclusion about number of layers; one layer with MIG welding is almost as thick as three layers with TIG welding with welding wire Ø 1mm.

    Three welding evaluation that is really important is visual examination, dye penetrant testing and corrosion test in order to choose which overlay welding method is suitable in boiler application.

  • 16.
    Van Meensel, Kim
    et al.
    Katholieke Universiteit Leuven, Belgium.
    Lietaert, Karel
    Katholieke Universiteit Leuven, Belgium; 3D Systems Leuven, Belgium.
    Vrancken, Bey
    Katholieke Universiteit Leuven, Belgium.
    Dadbakhsh, Sasan
    Katholieke Universiteit Leuven, Belgium.
    Xiaopeng, Li
    Katholieke Universiteit Leuven, Belgium; University of New South Wales, Sydney, Australia.
    Kruth, Jean Pierre
    Katholieke Universiteit Leuven, Belgium.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsev, Igor
    Central University of Technology, Bloemfontein, South Africa.
    Van Humbeeck, Jan
    Katholieke Universiteit Leuven, Belgium.
    Additively manufactured metals for medical applications2018In: Additive Manufacturing: Materials, Processes, Quantifications and Applications / [ed] Jing Zhang, Yeon-Gil Jung, Kidlington, U.K.: Butterworth-Heinemann, 2018, 1, p. 261-309Chapter in book (Refereed)
  • 17.
    Vilardell, Anna M.
    et al.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain.
    Cinca, N.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain..
    Concustell, A.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain..
    Dosta, S.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain.
    Cano, I. G.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain.
    Guilemany, J. M.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain.
    Cold spray as an emerging technology for biocompatible and antibacterial coatings: State of art2015In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, no 13, p. 4441-4462Article, review/survey (Refereed)
    Abstract [en]

    The use of coatings in biomaterials has been fundamental on the applicability of many medical devices and has helped improve mechanical properties such as wear and fatigue and biological properties such as biocompatibility and bioactivity of implant prosthesis, thus, in essence, ameliorating human quality life. The aim of the present paper is to give a review on cold spray (CS) coating systems that are emerging in orthopedics industry (internal fixation systems and prosthesis) as well as those for antibacterial purposes (in body and touch external surfaces). These studies are very new, the oldest dating from the half of last decade and most deal with the improvement of biocompatibility and bioactivity of hard tissue replacement; therefore, research on biocoatings is in constant development with the aim to produce implant surfaces that provide a balance between cell adhesion and low cytotoxicity, mechanical properties, and functionalization. CS offers many advantages over conventional high-temperature processes and seems to be able to become competitive in front of the low-temperature techniques. It is mainly cost effective, appropriate for oxygen-sensitive materials, and environmentally green. It basically involves the use of feedstock material in powder form, which is supersonically sprayed onto the appropriate substrate but without any melting as it occurs in conventional thermal spray processes. Biocompatible metallic materials and polymers have been successfully deposited by this method because it is based on the plasticity of the coating material; pure ceramic deposits, for example of hydroxyapatite, are still a challenge.

  • 18. Yadroitsev, I
    et al.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Yadroitsava, I
    Selective laser melting of Ti6Al4V alloy for biomedical applications: Temperature monitoring and microstructural evolution2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 583, p. 404-409Article in journal (Refereed)
  • 19.
    Yadroitsev, I
    et al.
    Université de Lyon, France.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Yadroitsava, I
    Université de , France.
    Johansson, S
    Linköpings universitet.
    Smurov, I
    Université de Lyon.
    Energy input effect on morphology and microstructure of selective laser melting single track from metallic powder2013In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 213, no 4, p. 606-613Article in journal (Refereed)
  • 20. Yadroitsev, Igov
    et al.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsava, Inna
    Titanium Alloys Manufactured by In Situ Alloying During Laser Powder Bed Fusion2017In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 69, no 12, p. 2725-2730Article in journal (Refereed)
    Abstract [en]

    This work is focused on the investigation and understanding of in situ processes in Ti-15%Mo and Ti6Al4V-1.38%Cu alloys by laser powder bed fusion (LPBF). In both materials, Mo and Cu were introduced as elemental powders into the precursor powder mixture. The effect of process parameters, i.e., energy input on surface morphology and homogeneity, was investigated. The importance of different thermophysical properties of blended powders is also discussed. The chemical composition of phases and phase distribution in sintered materials were investigated by means of scanning electron microscopy. The mechanical properties of in situ alloyed as-built LPBF specimens were determined. The results obtained developed knowledge that is important for understanding the in situ alloying process during LPBF, and they create a base for synthesizing new materials.

  • 21.
    Yang, Zhenkun
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Alternatives to hard chromium plating on piston rods2011Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
  • 22.
    Zemui, Simon
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Quenching and tempering hardness response of front axle steel beams: Different material properties during quenching and tempering2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this thesis was to investigate what the relation is between as-quench hardness and final surface hardness for steel beams is, depending on what tempering temperature is used. Also explain how chemistry, dimension and microstructure effects the final mechanical properties of the front axle beam. For this a review of literature concerning the effects was completed.Hardness measurement on the surface was performed on the ends of the beam (bottom and top). This hardness measurement was performed on 6 different front axle articles of the same material (41CrS4) and 2 different front axle articles of another material (40CrMo4). The relation diagram gives an estimation of what type of tempering temperature is needed to achieve the final hardness that is desired. Because the relation was done with some inconsistences it can’t be said to give a perfect answer. The relation diagrams only work for material 41CrS4 and 40CrMo4. For the core hardness test, 2 articles of 41CrS4 and one article of 40CrMo4 was measured on 5 different position on the cross-section, the beams for the respective articles were taken from quenched state and quenched+tempered. The beam dimensions have a significant effect when it comes to cooling down the part and achieve as close to uniform hardness as possible. Even though the Middle point of the I-section sample is one of the closest cores to the surface, it has a softer core compared with the other cores. While there exists hardness difference after quenching between different points in the core they even out after tempering. When comparing the core hardness with the surface hardness it can be said that the surface hardness is not as hard as the core because of decarburization. The microstructure analysis was done on 2 articles of 41CrS4 and one article of 40CrMo4. Samples from the 3 articles is taken from both the as-quenched state and quenched+tempered state. From the optical microscope it could be seen, that the surface of the beams decarbonizes leading to a higher amount of ferrite at the structure and softer surface. Because of this 15 mm into the material is harder than at-surface. Decarburization of the 41CrS4 steels made it so that what should have been a martensite and bainite dominated surface became a ferrite and bainite dominated.To decide the actual amount of retained austenite in the sample an XRD-analysis was performed. The XRD-analysis is done only for one article type of 41CrS4. From the front axle beam three samples of three different locations (bottom, middle, top) was taken for the analysis. For the theoretical calculation of the retained austenite vs the actual amount it can be said that is a very good representation of the total amount of retained austenite in the product. But the theoretical calculation deviates a bit from the actual amount at the top part of the beam.

  • 23.
    Åkefeldt, Jon
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Optimization of laser welding process: Hermetical weld between a medium carbon steel and a low carbon steel shim2017Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
1 - 23 of 23
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