AREVA NP Uddcomb AB wants to replace the material used for a specific valve seat used in boiling water reactors, BWR. Their solution is a weld overlay of different stainless steels composed of two buffer layers of the steel 309 MoL followed by two layers of the filler material SKWAM welded on type 316 stainless steel or carbon steel. The report focuses on the long term structural effects in the weld overlay due to the operating temperature in BWRs, in this case 270 °C. To investigate the thermodynamic stability in the weld overlay the computer software Thermo-Calc was used and a metallographic examination was carried out. The results from these procedures were compared and possible long term effects were discussed. Most likely spinodal decomposition is the most severe structural change that may appear in the material. At equilibrium conditions at the operating temperature ferrite is decomposed into Fe-rich and Cr-rich ferrite but since the kinetics is not included in the calculations it is not possible to determine the rate of decomposition.

Fast-moving consumer goods (FMCG) companies are being an innovative way to develop successful products in the market. This project focuses on the development of a salicylic acid cleanser using the development procedure implemented by a FMCG company, Vivere. Insights into cosmetology, material types, emulsion concepts, key parameters and important steps in the development of a cosmetic product are described in the report.  Such fabricated product did undergo different tests to assure the quality and stability of the product during long period of times, showing great stability, especially in good storage conditions for more than 120 days.  Furthermore, a scale-up test was made using two different homogenisers machines, JF-A 4000 and PMC-3000. The results were astounding, JF-A 4000 product samples showed great results with similar behaviour and quality to the laboratory sample, meanwhile, PMC-300 product samples showed a 3,04-fold higher viscosity than the laboratory sample and showed low homogenisation. Therefore, only JF-A 4000 homogeniser will be used for the future productions of the material.  Finally, an economic analysis was executed, concluding that the estimated number of units that should be sold before the project becomes profitable is 2190 units.

Adhesive bonding has become an essential joining method in the automotive industry specially with the recent focus on lightweight reduction. A major limiting factor to the widespread implementation of this joining method is concerns about environmental durability. Many research projects have been conducted to investigate the effect environmental exposure on cured adhesive joints, however, the effect that this exposure has on uncured bonds has been overlooked. This study, conducted in collaboration with Volvo cars, aims to investigate the degradation of mechanical properties caused by environmental exposure on uncured bonds and to provide practical recommendations on how to minimize its detrimental effect.  To achieve these objectives adhesive joints were manufactured by a crash resistant epoxy based adhesive and exposed to different climates for different ageing times and conditions. Afterwards, curing and mechanical testing were performed to assess the degradation of mechanical properties: shear strength, peel strength and fatigue life. Analysis of the results showed harsher climates to be linked to an increase in degradation of mechanical properties, an open bond exposure to accelerate the degradation process. Defects were introduced as pores and a decrease in adhesion to the adherend. Practical recommendations were made to minimize open bond exposure and harsh climates.

This thesis is about the investigation of the spectral interaction of electromagnetic radiation with metal powders. For this purpose, spectral data of powders for laser powder bed fusion processes are investigated in three papers using different techniques. In paper A the spectral radiation behavior of the laser interaction zone is considered, in paper B and C the absorbance behavior of different metal powders depending on their state and measurement method.   Paper A investigates the spectral signal of the process light generated by laser material interaction in laser powder bed fusion. The detection is performed by a coaxially guided measuring beam and a quasi-coaxial measuring beam simultaneously guided by another scanning optics. The signal characteristics depend on the angle of incidence of the measuring beam to the laser material interaction zone. Using high-speed recordings and optical simulations, a model for describing the signal behavior could be determined. The measured spectral intensity distribution representing the degree for energy coupling can be corrected with a correction factor over the whole field for solid materials. This correction includes a function describing the numerical aperture of the measuring channel and the laser intensity on the working field. For the investigated powder, the measurement signal fluctuated strongly and no transferable model could be formed. The reason for this was the different absorbance behavior of the powders investigated. Paper B therefore deals in detail with the spectral absorbance behavior of metal powders for additive manufacturing. Using a high-precision spectrometer, 39 powders were measured reflectively over a wide spectral range and the absorbance determined. By varying the degree of use, aging, grain size and impurities, various influence parameters are determined experimentally and discussed theoretically. Based on 20 derived laser wavelengths, technically usable wavelengths with better process efficiency and stability are proposed. From the obtained absorbance, the efficiency of energy coupling can be estimated and form a broad data base for the optimization of laser parameters. In order to perform the absorbance determinations also in situ in a laser powder bed fusion system paper C describes a possibility of an inline absorbance determination by high resolution coaxial imaging. A method is discussed for geometrically correct and gapless imaging of the processing plane, recorded through the laser optics. By imaging at six different wavelengths, metal powders can be distinguished by their absorbance spectrum and impurities can be detected. In an experimental implementation the functionality of the method is proven. The results are validated by optical simulations, ray tracing and comparative measurements with a high-precision spectrometer.

Combinations of different materials are increasingly used in the modern engineering structures. The driving forces of this trend are rising fuel costs, global warming, customer demands and strict emission standards. Engineers and industries are forced to improve fuel economy and cut emissions by introducing newly design engines and lightweighting of structural components. The use of lightweight materials in the structures has proved successful to solve these problems in many industries especially automobile and aerospace. However, industry still lacks knowledge how to manufacture components from polymeric materials in combination with metals where significant differences exist in properties. This thesis aims to demonstrate and generate the methodology and guidelines for hybrid joining of aluminium alloys to thermoplastics using friction stir welding. The developed technique was identified, optimized and evaluated from experimental data, metallography and mechanical characterization. The success of the technique is assessed by benchmarking with recent literatures. In this work, lap joints between aluminium alloys (AA5754, AA6111) and thermoplastics (PP, PPS) were produced by the friction stir welding technique. The specimens were joined with the friction stir welding tools under as-received conditions. Metallic chips were generated and merged with the molten thermoplastic to form a joint under the influence of the rotating and translating tool. The effects of process parameters such as rotational speed, translational speed and distance to backing were analyzed and discussed. The investigation found joint strength was dominated by mechanical interlocking between the stir zone and the aluminium sheet. The results also show that the joint strength is of the same order of magnitude as for other alternative joining techniques in the literature. / <p>QC 20150908</p>

Hybrid structures including aluminum-thermoplastic and aluminum-reinforced thermoplastic composite are increasingly important in the near future innovations due to its lightweight and high strength-to-weight ratio. A critical point for metal-polymer application is that sound joining of these materials is difficult to achieve owing to a large difference in surface energy and dissimilar structure between metal and polymer. In practice, two major joining methods for hybrid structures are mechanical joining and adhesive bonding. However, there are some drawbacks of these conventional methods such as stress concentration, long curing time and low reliability joints. A new novel metal-polymer hybrid joining is required to overcome these issues as well as manufacturing and cost perspectives. To this end, this work aims to develop a general methodology to apply friction stir welding techniques to join a wide range of thermoplastics with and without fibers to aluminum alloy sheets. The present work proposed an experimental study to attain insight knowledge on the influences of welding parameters on the quality of hybrid joints in term of the maximum tensile shear strength. This includes the role of tool geometries, welding methodology as well as material weldability in the investigation. The results showed that friction stir welding is a promising technique for joining of thermoplastic to aluminum. Microstructural observation showed that a good mixing between aluminum and thermoplastic as well as defect-free weldments were obtained. Tool geometries and welding speed are two factors that significantly contribute to the quality of friction stir welded hybrid joints. The results also demonstrated that weld fracture modes are associated with material mixing as well as interfacial bonding between aluminum and thermoplastic. An evaluation of the joint strength was benchmarked with the relevant literatures on hybrid joining. The results of proposed technique showed that the maximum tensile shear strength of friction stir welded joints were the same order of magnitude as the joints welded by laser welding.

Duplex stainless steels (DSS), with a ferritic-austenitic microstructure, are used ina wide range of applications thanks to their high corrosion resistance and excellent mechanical properties. However, efficient and successful production and joining of DSS require precise control of processes and an in-depth understanding o frelations between composition, processing thermal cycles, resulting microstructures and properties. In this study laser welding, laser reheating, and laser additive manufacturing using Laser Metal Deposition with Wire (LMDw) ofDSS and resulting weld and component microstructures and properties are explored. In the first part a lean FDX 27 duplex stainless steel, showing the transformation induced plasticity (TRIP) effect, was autogenously laser welded and laser reheated using pure argon or pure nitrogen as shielding gas. The weld metal austenite fraction was 22% for argon-shielding and 39% for nitrogen-shielding in as-welded conditions. Less nitrides were found with nitrogen-shielding compared to argonshielding. Laser reheating did not significantly affect nitride content or austenite fraction for argon-shielding. However, laser reheating of the nitrogen shieldedweld removed nitrides and increased the austenite fraction to 57% illustrating the effectiveness of this approach. Phase fraction analysis is important for DSS since the balance between ferrite and austenite affects properties. For TRIP steels the possibility of austenite tomartensite transformation during sample preparation also has to be considered. Phases in the laser welded and reheated FDX 27 DSS were identified and quantified using light optical microscopy (LOM) and electron backscatter diffraction (EBSD) analysis. An optimized Beraha color etching procedure was developed for identification of martensite by LOM. A novel step-by-step EBSD methodology was also introduced, which successfully identified and quantified martensite as well as ferrite and austenite. It was found that mechanical polishing produced up to 26% strain-induced martensite, while no martensite was observed after electrolytic polishing.In the second part a systematic four-stage methodology was applied to develop procedures for additive manufacturing of standard 22% Cr duplex stainless steel components using LMDw combined with the hot wire technology. In the four stages, single-bead passes, a single-bead wall, a block, and finally a cylinder with an inner diameter of 160 mm, thickness of 30 mm, and height of 140 mm were produced. The as-deposited microstructure was inhomogeneous and repetitive including highly ferritic regions with nitrides and regions with high fractions ofaustenite. Heat treatment for 1 hour at 1100 ̊C homogenized the microstructure, removed nitrides, and produced an austenite fraction of about 50%. Strength, ductility, and toughness were at a high level for the cylinder, comparable to those of wrought type 2205 steel, both as-deposited and after heat treatment. The highest strength was achieved for the as-deposited condition with a yield strength of 765 MPa and a tensile strength of 865 MPa, while the highest elongation of 35% was found after heat treatment. Epitaxial growth of ferrite during solidification, giving elongated grains along the build direction, resulted in anisotropy of toughness properties. The highest impact toughness energies were measured for specimens with the notch perpendicular to the build direction after heat treatment with close to 300 J at -10oC. It was concluded that implementing a systematic methodology with a stepwise increase in the deposited volume and geometrical complexity can successfully be used when developing additive manufacturing procedures for significantly sized metallic components. This study has illustrated that a laser beam can successfully be used as heat source in processing of duplex stainless steel both for welding and additive manufacturing. However, challenges like nitrogen loss, low austenite fractions and nitride formation have to be handled by precise process control and/or heat treatment. / Duplexa rostfria stål (DSS) är viktiga konstruktionsmaterial tack vare derasutmärkta mekaniska egenskaper och goda korrosionsbeständighet. Vid svetsningoch additiv tillverkning krävs noggrann styrning av parametrar och kunskap om processernas inverkan på mikrostrukturen för att uppnå önskade egenskaper.Lasersvetsning, värmebehandling med laser och additiv tillverkning i form av lasermetalldeponering med tråd (LMDw) har därför studerats för DSS. Det duplexa stålet FDX 27 lasersvetsades utan tillsatsmaterial och med argon ellerkväve som skyddsgas. Kvävgasskydd gav mer austenit och färre nitrider änargonskydd. En efterföljande laservärmebehandling löste upp nitriderna då kväve användes som skyddsgas och austenithalten ökade till 57%. Austeniten i FDX 27kan vid deformation omvandlas till martensit. Två metoder för identifiering av martensit utvecklades därför: en färgetsmetod för ljusoptisk mikroskopi samt en metod som utnyttjar bakåtspridda elektroner (EBSD) vid elektronmikroskopi.Som mest bildades 26% martensit vid mekanisk provpreparering medan elektropolerade prover endast innehöll austenit och ferrit. Procedurer togs fram för additiv tillverkning av komponenter, i 22% krom duplexa rostfria stål, med LMDw kombinerat med varmtrådsteknik. Slutprodukten var en 140 mm hög cylinder med 160 mm inre diameter och tjocklek av 30 mm. Mikrostrukturen var inhomogen med periodiskt omväxlande ferritiska områden med nitrider, och områden med stor andel austenit.Värmebehandling under 1 timme vid 1100oC eliminerade nitriderna och gav en homogen struktur med ca. 50% austenit. De mekaniska egenskaperna var, både före och efter värmebehandling, jämförbara med de typiska för motsvarande stål. Högst hållfasthet uppmättes före värmebehandling med sträckgränsen 765 MPa och brottgränsen 865 MPa, medan den största förlängningen var 35% efter värmebehandling. Slagsegheten var upp till 300 J vid -10oC men varierade med hur provstavens brottanvisning var orienterad relativt byggriktningen.Laser är en lämplig energikälla vid svetsning och additiv tillverkning av duplexa rostfria stål. Utmaningar som kväveförlust, låga austenithalter och nitridbildning kan hanteras med noggrann processkontroll och/eller värmebehandling.

The acceptance of additive manufacturing (AM) depends on the quality of final parts and the process repeatability. Recently, many studies have been dedicated to the establishment of the relationship between the process behavior and material performance. Phenomena such as laser-material interaction, melt pool dynamics, ejecta formation and particle movement behavior on a powder bed are of a particular interest for the AM community as these events directly influence the outcome of the process. Another aspect, which hinders the adoption of AM, is the need for cost-efficient powder materials and their sustainable processing and subsequent recycling.  The research work presented in this thesis, to a certain degree, covers the above mentioned scientific aspects and focuses on the behavior of gas and water atomized steel powders in laser powder bed fusion (LPBF).  Paper I demonstrates a comparative study of dissimilarly-shaped gas and water atomized low alloy steel powders regarding their processability, packing capacities, particle movement behavior and powder performance in LPBF. The impact of chemical composition and morphology of the powders on the process behavior was revealed. Powder spattering and melt pool instabilities were discussed in detail.  Paper II explains the role of ejecta in the recycled powder and the changing behavior of the material due to ejecta pick-up. The impact of multiple powder recycling on the degradation of low alloy steel powder in laser powder bed fusion was studied. Oxygen content, particle size and ejecta occurrence gradually increased after each recycling step and were identified as the main contributors to the property alterations observed in the powder during recycling. In addition, a direct correlation between the increase in oxygen with repeated recycling and a more frequent spatter ejection after each recycle was established.  Paper III is a successor of Paper I and contains a research on the particle movement and denudation behavior on a powder bed when using near-spherical and non-spherical steel powders. The influence of particle morphology on the dynamics of arbitrary-shaped powder particles was studied by applying an analytical correlation formula to calculate the drag force exerted on powder particles of various shape. Particle entrainment of gas and water atomized powders in front of the laser beam was measured, revealing a significant difference in the powder transfer towards the melt pool.

Wissenschaftliche Schriftenreihe, die Dissertationen der Professur Schweißtechnik beinhaltet. / Scientific series containing dissertations of the Professorship of Welding Engineering.

Within manufacturing of metallic components, machining plays an important role and is of vital significance to ensure process reliability. From a cutting tool design perspective,  tool macro geometry  design  based on physics based  numerical modelling  is highly needed  that can predict chip morphology.  The chip morphology describes the chip shape geometry and the chip curl geometry. The prediction of chip flow and chip shape is vital in predicting chip breakage, ensuring good chip evacuation and lower surface roughness.  To this end, a platform where such a  numerical model’s chip morphology prediction  can be compared with experimental investigation is needed and is the focus of this work. The studied cutting processes are orthogonal cutting process and nose turning process. Numerical models that simulate the chip formation process are employed to predict the chip morphology and are accompanied by machining experiments. Computed tomography is used  to scan the chips obtained from machining experiments and its ability to capture the variation in  chip morphology  is evaluated.  For nose turning process,  chip  curl parameters during the cutting process are to be calculated. Kharkevich model is utilized in this regard to calculate the  ‘chip in process’ chip curl parameters. High speed videography is used to measure the chip side flow angle during the cutting process experiments and are directly compared to physics based model predictions. The results show that the methodology developed provides  the framework where advances in numerical models can be evaluated reliably from a chip morphology prediction capability view point for nose turning process. The numerical modeling results show that the chip morphology variation for varying cutting conditions is predicted qualitatively. The results of quantitative evaluation of chip morphology prediction shows that the error in prediction is too large to be used for predictive modelling purposes.