Thermal Barrier Coatings (TBCs) are advanced material systems that are being used in the hot sections of gas turbines such as combustor, turbine blades, and vanes. The top ceramic coating in TBCs provides insulation against the hot gases and the intermediate metallic bond coat provides oxidation and corrosion resistance to the underlying turbine components. Durability of thermal barrier coatings is very important for the overall performance of the gas turbine. TBCs can fail in several different ways and there is a combination of more than one failure mechanism in most situations. One of the most widely used TBC is atmospheric plasma sprayed (APS) yttria stabilized zirconia (YSZ). Both the deposition technique and the TBC material have certain limitations. The main aim of this research is to study new TBC materials and/or new deposition techniques and compare with the conventional YSZ and understand their failure mechanisms during cyclic oxidation and hot corrosion. Thermal cyclic oxidation of a newly developed high purity nano YSZ thermal barrier coating has been studied. Cross sectional analysis of exposed as well as completely failed samples showed a mixed-type failure caused by crack propagation parallel to the bond coat/top coat interface. The majority of the damage occurred towards the end of the coating life. A finite element model has been developed to study the probability of crack growth along different paths that leads to the final failure. Hot corrosion mechanism in suspension plasma sprayed two-layer gadolinium zirconate/YSZ, three-layer dense gadolinium zirconate/gadolinium zirconate/YSZ, and a single-layer YSZ has been studied in the presence of sodium sulfate and vanadium pentoxide. The test results showed that gadolinium zirconate coatings were more susceptible to corrosion compared to YSZ coatings despite gadolinium zirconate coatings having lower reactivity with the corrosive salts. Thermal cycling behavior of a high chromium bond coat has been studied. Cross-sectional analysis showed formation of sandwich type microstructure with chromium rich oxide and alumina as the top and the bottom layers. Inter-diffusion of minor elements between different MCrAlY coatings – substrate systems has been studied using, diffusion simulation software, DICTRA. The simulation results showed that the diffusion of minor elements in the coatings is dependent on the rate of β phase depletion in the beginning. After the depletion of β phase there was no clear dependence of the coating composition on the diffusion of minor elements.

In recent years, the consequences of global warming have increased the discussion about the climate impact caused by humans and the fossil emissions. Sweden has decided to reduce the negative climate impact with a zero vision for the fossil carbon dioxide emissions in year 2045. In order to achieve this, great efforts and changes are needed both in the inhabitants' way of living but primarily in the base industry. The major cause is the use of fossil coal, which generates fossil carbon dioxide in the steel industry in particular. The fossil coal is added to the blast furnace in the steel process in forms of coke and coal, which reduces the iron and emits heat. The quality of the coke is important as it functions reducing agent, provides a mechanical support to the bed and enables the gas flow up through the blast furnace and enables dissolution of carbon in hot metal. Also, coke supplies energy from exothermic reactions between carbon and carbon dioxide that takes part in the blast furnace and the energy are further used for the heating and melting of the cold iron pellets. Due to these factors, the blast furnace process is dependent on coke for its function, which means that the entire process must be replaced if the steel production should work without fossil coal. However, there are many studies that have been done on how to replace some of the fossil coal with bio-coal, which is produced from biomass. If some of the fossil coal could be replaced by some bio-coal, this would mean that fossil carbon dioxide emissions would decrease and lead to a reduced climate impact. The process would still generate carbon dioxide, but on the other hand, a cycle would be formed because when biomass is grown, carbon dioxide is taken up, e.g. by the trees grown for this purpose. However, bio-coal does not have the same properties as fossil coal, which in turn affects the quality of the coke. Bio-coke is more reactive and more porous than fossil coke. In order to be able to replace fossil coke with bio-coke, it is likely necessary to pre-treat the biocoal before it replaces part of the fossil coal in the coke production. Bio-coal contains ash that acts as an internal catalyst. One theory is that if it is possible to produce a bio-coal with ash-free carbon structure, it can be used in the production of coke without having such a great effect on the coke quality. In this project, the ash's impact on the properties of bio-coal in coke was studied. Previous studies have shown that leaching is an effective method for removing ash from bio-coal. It can be leached in three different ways, either with water, weak acid or acid. However, it has been found that acid leaching has a certain impact on the carbon structure itself. For this reason, two types of bio-coal, torrefied Grot (forest residue) and torrefied sawdust were selected, which were leached both with water but also with weak acid in order to achieve an ash-reduced carbon structure. The acid selected was acetic acid, as it has been tested for similar purposes in previous studies. The leaching efficiency was evaluated by analysing the leachate with ICP-OES after leaching. According to the result, a significant part of the ash had been leached out, but the leaching with weak acid was much more effective than water leaching. To ensure that the carbon structure was not altered, light-optical microscopy was made which showed that the structure was intact. However, it was not possible to determine whether the pore sizes were changed after leaching and it is therefore relevant to investigate this further. Moreover, the leached II bio-coal replaced 5% of the fossil coal in the coal mixture for coke making. In addition to this, coke was also made with only the ash from the two bio-coals to see what effect the ash has on the coke quality. The result that was obtained from the TGA showed that the ash had a low impact on the reactivity of the coke. However, the coal structure of the coke had a great impact on the reactivity behaviour. Keywords: Bio-coke, bio-coal, leaching, ash, coke quality, carbon structures, torrefied sawdust

Residual compressive stresses can be used to increase the lifetime of parts under cyclic stress as they negate the applied tensile stresses that cause crack initiation and propagation in the material. The goal of this project was to investigate methods to induce stresses, their advantages and disadvantages as well as depth and magnitude of induced stresses, and also to find methods of analyzing the induced residual stresses. This was done on behalf of Epiroc Drilling Tools AB in order for them to induce stresses on the insides of their long, narrow and hollow rods, where stress induction is difficult. Shot peening was used as a reference as that is the method currently in use by the company. The results show that the two most promising methods are cavitation peening and laser shock peening; two relatively new methods with large magnitudes and depth of induced stress as well as a great capability of inducing stresses on the hard-to-reach insides of the rods. Ultrasonic needle peening, ultrasonic shot peening as well as induction hardening, cryogenic treatment and friction stir processing were also investigated. Methods of analyzing the stresses include X-ray diffraction and slitting, hole drilling and ultrasonic methods.

This thesis work was done to get a fundamental knowledge of the mechanical and microstructural properties of 316L stainless steel fabricated with the additive manufacturing technique, laser powder-bed fusion (L-PBF). The aims of the thesis were to study the mechanical and microstructural properties in two different building orientations for samples built in two different machines, and to summarize mechanical data from previous research on additive manufactured 316L. Additive manufacturing (AM) or 3D-printing, is a manufacturing technique that in recent years has been adopted by the industry due to the complexity of parts that can be built and the wide range of materials that can be used. This have made it important to understand the behaviour and properties of the material, since the material differs from conventionally produced material. This also adds to 316L, which is an austenitic stainless steel used in corrosive environments. To study the effect of the building orientation, samples of 316L were built in different orientations on the build plate. The density and amount of pores were also measured. Tensile testing and Charpy-V testing were made at room temperature. Vickers hardness was also measured. Microstructure and fracture surfaces were examined using light optical microscope (LOM) and scanning electron microscope (SEM). The microstructure of the 316L made with L-PBF was found to have meltpools with coarser grains inside them, sometime spanning over several meltpools. Inside these coarser grains was a finer cellular/columnar sub-grain structure. The tensile properties were found to be anisotropic with higher strength values in the orientation perpendicular to the building direction. Also high dense samples had higher tensile properties than low dense samples. The impact toughness was found to be influenced negatively by high porosity. Hardness was similar in different orientations, but lower for less dense samples. Defects due to lack of fusing of particles were found on both the microstructure sample surfaces and fracture surfaces. The values from this study compare well with previous reported research findings.

Att ha statistiskt säkerställda mått på slitstyrkan hos precisionsverktyg så som tryckeriraklar kan användas för att underlätta vidare utveckling samt marknadsföring av dessa produkter. I följande examensarbete har utveckling av en metod för att studera slitstyrkan hos tryckeriraklar genomförts. Studierna har genomförts i en testrigg som simulera en rotogravyrtryckeripress. Examensarbetets mål är att utveckla en metod för att testa slitstyrkan av olika rakelprodukter i testriggen samt att tillämpa denna metod för att få dokumenterade jämförande tester mellan fem olika produkttyper. Resultaten av testerna visar nötningen av rakelbladen med lamellängdförlust och viktförlust som mått på nötningen. Det resultat som definitivt kan konstateras är att Produkt C visar lägre slitage än Produkt A. Lamellängdförlust rekommenderas som mått på slitaget under fortsatta studier för att underlätta jämförelser mellan blad med och utan ytbeläggning. För att erhålla högre repeterbarhet rekommenderas fortsatta studier med avseende på färgens korrosivitet, temperatur och viskositet. Vidare studier rekommenderas även för olika färgtyper, då med mjukare pigment och längre testlängd för att se huruvida det ökar repeterbarheten. Vidare studier bör genomföras med avseende på de olika nötningsmekanismer som rakelbladen utsätts för under testerna. / Having statistically acquired measurements on the wear of precision tools like doctor blades can be used to assist further development and marketing of these products. In this thesis the development of a testing method for studying the wear on doctor blades has been conducted. The tests have been performed in a testing rig to simulate a rotogravure printing press. The goal of the thesis work is to develop a method for testing the wear resistance of five different doctor blade products in a testing rig and then applying this method to get a documented comparative study between the different doctor blade products. The results from the testing shows wear of the doctor blades using lamella length loss and weight loss and units of measurement.The results clearly show that Product C shows less wear than Product A. Lamella length loss is the recommended unit of measurement for measuring the wear on the doctor blades, this makes it possible to compare coated and uncoated blades. For a higher repeatability of the tests further studies are recommended with the paints corrosiveness, temperature and viscosity in mind. Further studies are also recommended into different kinds of paint, with softer pigments while increasing the test length. Further studies should also be performed to gain a greater understanding of the different wear mechanisms that contribute to the wear of the doctor blades during testing.

This study investigates the effect of strain rate on fracture properties of Ferritic-Pearlitic Ductile Iron. A series of dynamic three point bending tests, with various load application rates, are conducted on Charpy V-notch specimens, in room temperature and approximately -18 °C. The tests are performed in a custom-made fixture and during the tests, force and displacement data are recorded. A XFEM (Extended Finite Element Method) model of the test setup has been established and material data from the tests are used as input to the model. The test results show a strong dependency of the strain rate regarding the force needed for crack initiation. Moreover, it can be concluded that low temperature makes the material very brittle, even at low load application rates.

In present thesis, the fundamental studies on the reaction between MgO based refractories and slag were undertaken for the development of a carbon-free bonding MgO lining material. Alumina was selected as a potential binder material. Due to MgO-Al2O3 chemical reaction, the developed refractory was bonded by MgO·Al2O3 spinel phase. To begin with, an investigation of the dissolution process of dense MgO and MgO·Al2O3 spinel in liquid slag was carried out. To obtain reliable information for dissolution study, a new experimental method was therefore developed. In this method, a cylinder was rotating centrally in a special designed container with a quatrefoil profile. This method also showed a good reliability in revealing the dissolution mechanism by quenching the whole reaction system. The experimental results showed that the dissolution process of MgO and spinel was controlled by both mass transfer and chemical reaction. It was found that the rapid dissolution of spinel was mainly because of its larger driving force. To improve the resistance against slag penetration, two aspects were studied to develop carbon-free MgO refractory. First, colloidal alumina was used and the effect of its addition into MgO matrix was investigated. The use of colloidal alumina was to form bonding products in the grain boundary of MgO. The results showed that the alumina addition greatly improved the resistance of MgO based refractory against slag penetration in comparison with the decarburized MgO-carbon refractory. It was found that the improvement of resistance was mainly related to the spinel-slag reaction products of CaO·Al2O3 and CaO·MgO·Al2O3 solid phases at the grain boundaries. Second, the effect of particle size distribution on the penetration resistance of MgO was investigated. The most profound improvement against the slag penetration was obtained by using a proper particle size distribution. The results highlighted the importance of considering the refractory structure. Experiments were undertaken to investigate the dissolution mechanism of different types of MgO based refractories in liquid slag. It was observed that the dissolution of spinel bonded MgO refractory was much slower than the decarburized MgO-carbon refractory. The primary dissolution in spinel bonded MgO refractory occurred at the slag-penetrated layer, and the removal of this layer by peeling off enhanced the dissolution rate rapidly. / <p>QC 20170918</p> / European RFCS LEANSTORY project

High quality powder steel is manufactured through gas atomization at Erasteel Kloster AB in Söderfors. During their batches they have a problem with varying weight of capsules which can cause problems with bending capsules and unreliable exchange. Bent capsules risk damaging the equipment and cannot be used.The work was performed with the purpose to investigate the source for varying weights of capsules during batches and with the goal to account for a solution on how the varying capsule weights can be reduced.Powder samples were taken during five batches aiming to investigate the cause for varying capsule weights. The powders characteristics were analyzed with different methods which presented the powders size distribution, fill density, tap density and flowability. The Lubanska equation which calculates powders mean diameter was simplified and adjusted for the Erasteel plant with the intention to control gas pressure depending on the metal flow rate.Analyzes showed that the powder size distribution was changing during every batch. The amount of larger particles decreased more than the amount of small particles increased meanwhile the width of the powders size distribution decreased. This gave the largest width of size distribution half-way into the batch and the highest capsule weights were obtained at this moment.The simplified equation was applied to the moment when highest capsule weights was obtained and gave guidelines on how the gas pressure should be controlled to achieve similar size distribution. Further analyzes showed that the metal flow rate was proportional to the gas temperature due to it is measured after being in contact the melt stream.Since the equation was simplified and verified on five batches more tests needs to be extracted. It needs to be done not only to get a more reliable equation but also for an opportunity to test it in practice. With samples collected from more batches, there is a possibility to control the gas pressure with gas temperature and an automatic control of the gas pressure could be performed. / På Erasteel Kloster AB i Söderfors tillverkas högkvalitativt pulverstål genom gasatomisering. De har ibland under deras körningar problem med varierande kapselvikter vilket kan ge problem med att kapslar veckas vid komprimering samt opålitligt utbyte. Veckade kapslar riskerar att skada komprimeringsutrustningen samtidigt som kapseln måste skrotas. Arbetet utfördes i syftet att undersöka orsaken till varför kapselvikterna varierar under chargerna och med målet att redogöra för hur variationerna på kapselvikterna kan minskas. Under fem körningar togs pulverprover ut för att undersöka orsaken till varför kapselvikterna varierar. Pulvrets egenskaper analyserades med olika metoder vilka gav pulvrets storleksfördelning, fylldensitet, skakdensitet samt flytbarhet. Den Lubanska ekvationen för att beräkna pulvers medeldiameter vid gasatomisering förenklades och anpassades till Erasteels anläggning för att anpassa gastryck efter metallflöde. Analysen visade att pulvrets storleksfördelning förändrades under samtliga körningar. Mängden stora pulverkorn minskade mer än vad mängden små pulverkorn ökade under atomiseringen. Detta medförde att den största variationen av stora och små pulverkorn var halvvägs in i chargen och vid denna tidpunkt erhölls även de högsta kapselvikterna. Den förenklade ekvationen gav, med hjälp av tidpunkten då kapselvikterna var som högst, riktlinjer för hur gastrycket bör styras för att uppnå liknande storleksfördelning. Ytterligare analyser visade att gastemperaturen var proportionellt mot metallflödet, då temperaturen mättes efter att gasen varit i kontakt med det rinnande stålet. Eftersom den tillämpade ekvationen förenklades och verifierades mot endast fem körningar borde fler tester utföras. Detta för att ge en mer tillförlitlig styrning samt möjligheten att testa ekvationens riktlinjer i praktiken. Med provuttag under flera charger finns möjligheten att styra gastryck mot gastemperatur och med hjälp av detta skapa en automatiserad styrning.

Efficient measurement methods for comminution properties are an important prerequisite for testing the variability of an ore deposit within the geometallurgical context. This involves the investigation of effects of mineralogy and mineral texture on the breakage of mineral particles. Breakage properties of mineral particles are crucial for the liberations of minerals and the energy required for that. For process optimization and control purposes, comminution indices are often used to map the variation of processing properties of an entire ore body (e.g. Bond work index). Within the geometallurgical approach this information is then taken up when modelling the process with varying feed properties. The main focus of this thesis work has been to develop a comprehensive geometallurgical testing framework, the Geometallurgical Comminution Test (GCT), which allows the time and cost efficient measurement of grinding indices and their linkage to mineralogical parameters (e.g. modal mineralogy or mineral texture, mineral liberation). In this context a small-scale grindability test has been developed that allows estimating the Bond work index from single pass grinding tests using small amounts of sample material. Verification of the evaluation method and validation was done with different mineral systems. For selected samples the mineral liberation distribution was investigated using automated mineralogy. By transferring the energy-size reduction relation to energy – liberation relation new term liberability has been established. As part of the experimental investigations, mineralogical parameters and mineral texture information were used for predicting breakage and liberation properties. Patterns for describing the breakage phenomena were established for a set of iron oxide ore samples. The determined breakage patterns indicated that the specific rate of mineral breakage slows down when reaching the grain size of mineral particles, thus allowing maximizing mineral liberation significantly without wasting mechanical energy. / CAMM

The need to produce lighter components due to environmental aspects and the development of electrical vehicles represents an opportunity for cast aluminium-silicon alloys. With high specific strength, good castability, high corrosion resistance and recyclability, these alloys offer an attractive combination of properties as an alternative to steel, cast iron and titanium-based components in certain applications. To take advantage of such a combination of properties, there is a need to ensure that they can be reliably achieved. In other words, high performing components need to be produced. For that, the production cycle, from alloy selection and melt preparation, to the casting and heat treatment of the component must be understood and controlled as a whole. The different steps in the production cycle will affect the microstructure of the components and hence the resulting mechanical properties. Understanding the relation between the different steps in the production cycle, its consequences on the microstructural features and on the mechanical properties constitutes the aim of this thesis. Experiments applying state-of-the-art knowledge regarding effect of casting process, alloying system and post-process variables were performed aimed at achieving properties similar to those of high pressure die casting (HPDC) components. Different melt quality determination tools were evaluated on three different EN AC-46000 melt qualities. The influence of modification, grain refinement and both treatments together was assessed on an Al-10Si alloy solidified under different cooling rates. The tensile behaviour and the impact of features such as secondary dendrite arm spacing (SDAS) or grain sizes was quantified. It was corroborated that by appropriate selection and control of such alloying system, process and post-process variables it is possible to achieve HPDC EN AC-46000 tensile and fatigue properties through a T5 treated sand cast EN AC-42100 alloy. On the other hand, the available techniques for melt quality assessment are inadequate, requiring further analysis to successfully identify the melt quality. Additionally, it was observed that decreasing the melt quality by additions of 25 wt.% of machining chips did not significantly decrease the tensile properties but slightly increased the variation in them. In relation to the modification and grain refinement of Al-10Si alloys it was concluded that with the slowest cooling rate tested, additions of only grain refiner did not successfully produce equiaxed grains. For cooling rates corresponding to dendrite arm spacings of 15 μm and slower, combined additions of grain refiner and modifier can lead to higher tensile properties compared to the corresponding separate additions. SDAS was observed to describe flow stress through the Hall-Petch equation but grain size did not show a physically meaningful relationship. Furthermore, beginning of cracking was detected in the plastic deformation region at dendrite/eutectic boundaries and propagated in a trans-granular fashion.