Laser-assisted machining has been considered as an alternative for difficult-to-machine materials such as metallic alloys and ceramics. Machining of some materials such as high chromium alloys and high strength steels is still a delicate and challenging task. Conventional machines or computer numerical control (CNC) machines and cutting tools cannot adapt easily to such materials and induce very high costs for operations of rough machining or finishing. If laser-assisted machining can be implemented successfully for such materials, it will offer several advantages over the traditional methods including longer tool life, shorter machining time and reduced overall costs. This thesis presents the results of the research conducted on laser assisted machining of hard to wear materials used in making heavy duty mineral processing equipment for the mining industry. Experimental set up using a high power Nd:YAG laser beam attached to a lathe has been developed to machine these materials using cubic boron nitride (CBN) based cutting tools. The laser beam was positioned so that it was heating a point on the surface of the workpiece directly before it passed under the cutting tool. Cutting forces were measured during laser assisted machining and were compared to those measured during conventional machining. Results from the experiments show that with the right cutting parameters and laser beam position, laser assisted machining results in a reduction in cutting forces compared to conventional machining. A mathematical thermal model was used to predict temperatures within the workpiece at depths under the laser beam spot. The model was used to determine the effect of various cutting and laser parameters on the temperature profile within the workpiece. This study shows that laser assisted machining of hard to wear materials such as high chromium white cast iron shows potential as a possible economical alternative to conventional machining methods. Further research is needed before it can be introduced in industry as an alternative to conventional machining.

This thesis deals with the heat evolution duringsolidification and its relation to the formation of porosity.It intends to improve the current understanding of theformation of porosity in cast materials with special interestin nodular cast iron and the spray forming process. Twodifferent systems, a Fe-based alloy, Cast iron, and a Ni-basedalloy, Inconel 625, are examined. The effect on the heatevolution of the morphology and the processing parameters inspray forming are treated. An evaluation of the microstructural features, segregationbehavior and physical properties such as latent heat of fusionis performed byusing thermal analysis under cooling ratesranging from 0.1 to 104 K/s. In order to achieve this amodified differential thermal analysis (DTA) equipment, amirror furnace and levitation casting are used. Results arepresented in terms of the fraction of solidified, the coolingrate and the microstructure observed. The measured latent heatof fusion is not constant throughout the solidificationprocess. Variations in morphology and cooling rate affect therelease of the latent heat. A thermodynamic model is used to describe the experimentalobservations and to explain the formation of pores in nodularcast iron by taking into consideration the formation of latticedefects during the liquid/solid transformation. In this casethe formation of porosity is regarded as a consequence ofchanges in the volume fraction ratio graphite/ during thesolidification process. A numerical model of the spray forming process is developedby means of CFD modelling and compared with experimentalmeasurements performed in an industrial facility. Stagnationpressure measurements provided information about the gas flowvelocity and an analysis of the overspray powder providedinformation about the particle thermal history. Evaluation ofthe deposit was also performed. It is observed that the processconditions in spray forming promote non-equilibriumsolidification even though solidification at the deposit occursat a lower rate. In this case the porosity formed near theinterface substrate/deposit depends largely on the substratetemperature. The presence of certain reactive elements, such astitanium, affects the porosity levels in the rest of thedeposit. <b>Keywords:</b>Thermal Analysis, Nodular Cast Iron, Inconel625, CFD, Flow Assesment, Multiphase Flow, Spray Deposition,Microporosity, Superalloys

This study focuses on joining pearlitic ductile cast iron with low carbon steel by welding and investigation of this joint in microstructural and mechanical viewpoints. For this purpose E355 steel and GJS600-3 cast iron were joined using metal active gas (MAG) welding process by G3Si1 filler wire. The joining process is shaped mainly by the problems related to the low weldability of cast. Preheating was applied to prevent formation of cooling cracks and effects of post weld heat treatments (PWHT) were surveyed. Micro examination and micro hardness tests were applied to characterize the general microstructure. Grain size measurements were done for E355. Hardness profiles, tension and impact toughness properties were designated via mechanical tests. Fatigue behavior was surveyed and general fracture characteristics were determined via scanning electron microscopy (SEM) examinations. According to study it was concluded that successful weld joint could be formed between the materials by suitable preheating. Formation of ledeburitic white cast iron and martensite in heat affected zone of cast piece was witnessed. It was possible to lower high hardness values of these phases gradually by increasing post weld heat treatment temperatures. The weld joint behaved superior to the base metals under tension and fatigue tests. In tension tests failure occurred at E355 base metal whereas fatigue loading resulted failure at GJS600-3. A great impact toughness variation was determined between two pieces. It is seen that heat treatments had minor effect on mechanical test results except hardness. The study was concluded that a useful fusion weld joint between these materials can be built.

<p>This thesis deals with the heat evolution duringsolidification and its relation to the formation of porosity.It intends to improve the current understanding of theformation of porosity in cast materials with special interestin nodular cast iron and the spray forming process. Twodifferent systems, a Fe-based alloy, Cast iron, and a Ni-basedalloy, Inconel 625, are examined. The effect on the heatevolution of the morphology and the processing parameters inspray forming are treated.</p><p>An evaluation of the microstructural features, segregationbehavior and physical properties such as latent heat of fusionis performed byusing thermal analysis under cooling ratesranging from 0.1 to 104 K/s. In order to achieve this amodified differential thermal analysis (DTA) equipment, amirror furnace and levitation casting are used. Results arepresented in terms of the fraction of solidified, the coolingrate and the microstructure observed. The measured latent heatof fusion is not constant throughout the solidificationprocess. Variations in morphology and cooling rate affect therelease of the latent heat.</p><p>A thermodynamic model is used to describe the experimentalobservations and to explain the formation of pores in nodularcast iron by taking into consideration the formation of latticedefects during the liquid/solid transformation. In this casethe formation of porosity is regarded as a consequence ofchanges in the volume fraction ratio graphite/ during thesolidification process.</p><p>A numerical model of the spray forming process is developedby means of CFD modelling and compared with experimentalmeasurements performed in an industrial facility. Stagnationpressure measurements provided information about the gas flowvelocity and an analysis of the overspray powder providedinformation about the particle thermal history. Evaluation ofthe deposit was also performed. It is observed that the processconditions in spray forming promote non-equilibriumsolidification even though solidification at the deposit occursat a lower rate. In this case the porosity formed near theinterface substrate/deposit depends largely on the substratetemperature. The presence of certain reactive elements, such astitanium, affects the porosity levels in the rest of thedeposit.</p><p><b>Keywords:</b>Thermal Analysis, Nodular Cast Iron, Inconel625, CFD, Flow Assesment, Multiphase Flow, Spray Deposition,Microporosity, Superalloys</p>

The work presents the research of high-strength cast iron used for manufacturing of large grinding structures with dross layer and with non-homogeneous heat treatment volumes that remains inside during manufacturing process and subjected to high-cycle loading. The original research methodology used for investigations allowed to obtain the results of high-cycle loading. Obtained results have been used to improve the structural elements calculation methods.

The work presents the research of high-strength cast iron used for manufacturing of large grinding structures with dross layer and with non-homogeneous heat treatment volumes that remains inside during manufacturing process and subjected to high-cycle loading. The original research methodology used for investigations allowed to obtain the results of high-cycle loading. Obtained results have been used to improve the structural elements calculation methods.

The influence of casting voids on spheroid cast iron cracking threshold is investigated. The experimental results and their analytical and numerical analysis basing on linear fracture mechanics is presented. / Nagrinėjamas liejimo tuštumų poveikis stipriojo ketaus pleišėjimo slenksčiui. Pateikiami eksperimentiniai rezultatai ir jų analitinė bei skaitinė analizė, remiantis tiesine irimo mechanika. / Исследуется влияние литейных пустот на порог трещиностойкости чугуна с шаровидным графитом. Представлены результаты экспериментального исследования и их аналитический и численный анализ, опираясь на линейную механику разрушения.

Nagrinėjama liejimo tuštumų įtaka konstrukcinių elementų iš stipriojo ketaus stiprumui esant daugiacikliam apkrovimui. Eksperimetiškai nustatytas pleišėjimo slenksčio mažėjimas prie labai mažo plyšio plitimo greičio tiriamas analitiniais ir skaitiniais metodais, remiantis tiesine irimo mechanika. Pristatoma bandinių paviršiaus fraktografinė analizė. Siūloma patobulinta stiprumo skaičiavimo metodika. / The influence of casting voids on spheroid cast iron structure elements high-cycle fatigue strength is investigated. The experimentally established cracking threshold decrease at very small crack growth rate is investigated using analytical and numerical methods basing on linear fracture mechanics. The specimen surface fractographic analysis is presented. The improved strength calculation method is proposed. / Исследуется влияние литейных пустот на прочность элементов конструкций из чугуна с шаровидным графитом. Экспериментально установленное снижение порога трещиностойкости при очень малой скорости распространения трещины исследуется аналитическими и численными методами, опираясь на линейную механику разрушения. Представлен фрактографический анализ поверхности образцов. Предлагается усовершенствованная методика расчёта прочности.

The impact on human health caused by lead release has resulted in stringent lead regulations, which limit the drinking water concentration of lead to 10µg/L. In order to meet regulation guidelines, sources of lead are being removed from the distribution system and premise plumbing. Lead service lines (LSLs) are replaced to minimize the effect of lead release, with LSL contributing as much as 50-75% of total lead at the tap. Adsorption of lead on galvanized iron corrosion scales have been shown to increase lead release in LSL replacements, which is very concerning for utilities considering replacing the LSLs. Adsorption of lead on to iron minerals has been hypothesized as a mechanism for lead exposure. With the significant presence of unlined cast iron pipes in Halifax, the objective of this thesis was to determine the relationship between the iron particles found in cast iron pipes and lead release at the tap.

The market for renewable energy and an international power grid is constantly growing. This project has focused on the installation and protection methods for offshore power cables. Long distance cables over e.g. oceans and smaller distances within offshore wind farms. The focus is on three different materials for the protection task; concrete, cast iron and plastics. These materials have been evaluated in aspect to strength, life-length, reliability and environmental impact. Snapp products of Sweden AB have developed a cable protective pipe of polypropylene for offshore usage. This product and its opportunities are thoroughly investigated.