Cemented carbides (WC-Co) are powder metallurgical products produced by liquid phase sintering. WC-Co is widely used for making a large variety of cutting tools, such as drills and inserts turning applications, due to its great mechanical properties, where the hardness of the WC grains is combined with the toughness of the of the Co binder. WC grain size and grain size distribution are the two most important factors to control the mechanical properties of the products. This study examined the grain growth dependence of different milling and sintering times. The resulting grain size and grain size distribution were measured using image analysis on scanning electron microscopy images (SEM) and by using electron backscatter diffraction (EBSD). In addition, the correlation between hardness and coercivity, the most common indirect measures of grain size, and different methods of calculating average grain radius were investigated. An attempt was also made to study the contribution of defects to grain growth. This work also includes an overview of various grain growth equations and a numerical implementation of these. Experimental results show that for shorter sintering times, powders milled for short times (15 min and 1 h) have larger average grain radii. There is a crossover after 6 to 8 h of sintering, where the powders milled for a long time (40 h and 200 h), have larger average radii. The measured hardness values correlate well with the average grain radius calculated from the grain surface area and the coercivity correlates with the established equations. EBSD measurements detected boundaries that could not be detected by image analysis, and that were not Sigma 2 boundaries. It is likely that these boundaries are either low energy boundaries or boundaries between grains that are very closely oriented. Comparing heat-treated powder with the untreated resulted in a lower average grain size after sintering for the heat-treated powder. None of the growth equations investigated in this work could fully describe the experimental grain growth. Through increased understanding of the grain growth, the growth can be controlled and the end product can have the desired tool properties. The occurrence of abnormal grains in cutting tool applications can cause breakage, which is especially important to avoid in applications such as PCB drills. A correlation between hardness and grain size provides further means for cheap and fast indirect measures of the grain size in production. / Hårdmetall är ett pulvermetallurgiskt material som tillverkas genom smältfassintring och som kännetecknas av hårdhet, styvhet och god slitstyrka. Volframkarbidens (WC) kornstorlek och kornstorleksfördelning är två viktiga faktorer för att kontrollera de mekaniska egenskaperna i hårdmetall. I den här studien har korntillväxtens beroende på malning och sintring undersökts. WC-Co maldes och sintrades fyra olika tider och kornstorleksfördelningen mättes med bildanalys på svepelektronmikroskopbilder samt med ``electron backscatter diffraction'' (EBSD). I arbetet har även korrelationen mellan hårdhet, koercivitet och olika sätt att beräkna medelkornstorleken undersökts. Ett försök har också genomförts för att studera hur defekterna i det malda pulvret påverkar korntillväxten. I arbetet har även ett flertal olika tillväxtekvationer modellerats numeriskt och för och nackdelar med de olika tillväxtekvationerna har vägts mot varandra. En lång maltid (40 h och 200 h) visade sig ge liten kornstorlek för sintring kortare än 6 h, men för sintringar längre än 8 h gav istället kort malning (15 min och 1 h) den mindre kornstorleken. Det visade sig att uppmätt hårdhet korrelerar bäst med den medelkornstorleksradie som räknats fram från kornytan. I EBSD mätningarna kunde man observera ett flertal korngränser, utöver Sigma 2 korngränser, som inte hade detekterats med bildanalys. Värmebehandlingen av det malda pulvret minskade korntillväxten under efterföljande sintring. Ingen av de undersökta tillväxtekvationerna kunde beskriva de experimentella resultaten fullt ut. Genom ökad förståelse för korntillväxt kan man kontrollera tillväxten och slutprodukten kan få önskade egenskaper. Förekomsten av abnorm korntillväxt i skärverktyg i hårdmetall är en av de vanligaste kritiska defekterna och det är speciellt viktigt är undvika korntillväxt i tillverkning av små verktyg, som till exempel kretskortsborrar. Hårdhet och koercivitet är de vanligaste indirekta mätmetoderna för att mäta kornstorlek i produktion. En bra korrelation mellan kornstorlek och indirekta mätmetoder ger utökade verktyg för snabba och billiga mätningar.

Concrete is good as a construction material regarding fire and its properties regarding strength. However, the concrete expands and cracks due to fire resulting in structural damage. According to the literature the concrete usually loses its strength during and after fire exposure due to themechanical and physical changes.Concrete consists of cement, water, aggregates of different sizes, and usually some sort of plasticiser depending on its final use. Globally the concrete production releases about 4.5 billionmetric tons of carbon dioxide, which is about 8% of all the emissions of carbon dioxide in the world (Naturskyddsföreningen, 2022).The main components in cement are limestone and marlstone which are melted and turned to clinker. The clinker is mixed with sand and gypsum to make cement. Due to the high releases of carbon dioxide from the production of cement and the destruction of the environment mining of the raw materials, Sweden had a concrete-crisis in the summer of 2021, this was due to the government denied the main cement company Cementa AB to continue to mine limestone on the island of Gotland. Due to this decision new sustainable components to replace the components to produce concrete is critical. An alternative material called biochar may be suitable as a component in concrete. Biochar is a renewable product from pyrolysis of biomass. The favorable properties of biochar such as low density, high specific area and low thermal conductivity has the potential to lower the carbon footprint of concrete. This thesis evaluates the properties and performance for different biochar ratios mixed within concrete before and after exposure to fire in a furnace that followed the standard ISO 834 curve up to 650 ℃. In particular, experiments were conducted to observe how the mechanical properties (e.g., tensile and compressive strengths) are affected by exposure to fire that caused a temperature rise of up to 650 ℃. By analyzing the results from the experiments, it is seen that the workability of the concrete decreases with higher ratios of biochar due to the biochar’s water absorption properties. The compressive and tensile strength tests before fire exposure, for both aggregate and cement replaced samples, resulted in the average strength decreasing with higher ratios of biochar. Interestingly, iiithe results after fire exposure represented higher compressive strengths for both cement and aggregate replaced samples for all ratios of biochar. However, the tensile strength after fire exposure generally decreased with higher ratios of biochar. Differential scanning calorimetry and infrared spectroscopy were performed to gain an insight into the reason for the increase in compressive strength after fire exposure. Most probably, when the silica, present in the cement, was exposed to 650 °C under fire, it softened and fused the other components, which led to stronger compressive strengths.