Over the years, industrial partners experienced issues related to inconsistent free ferrite in gray cast iron. In the course of a hot summer and a cold winter, machinability balance varies up to 350%. During warm months it is better and cold months worse. The inconsistent machinability increases the scrap rates by up to 400% and reduces tool life by up to 70%. The ultimate objective of this research is to collaborate with an automotive industrial partner to investigate the periodic machinability variability of gray cast iron engine sleeves, with a goal to reduce the cost and scrap rate of tool inserts. In this study, a significant amount of work was conducted concerning sample preparation for a metallography check. Samples from different months with varying amount of “free ferrite” were collected to study the seasonal effect on their machinability and high-speed machining under similar industrial conditions. Furthermore, a room temperature age strengthening of gray cast iron was conducted to demonstrate how the hardness increase from aging could improve the machinability of gray cast iron. A CBN insert is the second hardest cutting tool after the diamond insert, and is widely used in industry for machining cast iron. It has a high cutting speed is commonly used due to its high hardness and impressive wear resistance. It is known that gray cast iron can naturally age at room temperature or artificially age under a controlled temperature. Under different aging temperatures and times, gray cast iron exhibits a greater hardness after age strengthening, which affects the CBN tool life. The latter is usually limited by flank wear length, however the content of free ferrite in gray cast iron can generate ferrous built-up on the CBN cutting edge and significantly shorten the tool life of the CBN cutting tool. / Thesis / Master of Applied Science (MASc)

This research study talks about the possible influence of gray cast iron microstructure on the corrosion properties of the brake rotor and the effect of stiction. Three Gray cast iron rotors with fully pearlitic microstructure and below 5% volume content of ferrite were studied in this research to understand their microstructural influence over corrosion. The selected gray cast iron rotors were friction tested against a 2009 Original Equipment Manufacturer (OEM) Ford F150 brake pad using scaled-down SAE J2522 standard test. Tested samples were later subjected to GMW16696 standard test, to identify the breakaway forces indirectly defining the corrosion resistance of the friction material used. The results show that the degree of corrosion and breakaway forces observed are greatly influenced by the graphite content quantified from quantitative analysis techniques adopted. Rotor with higher graphite content observed higher breakaway force and higher oxygen content compared to the other two studied rotors. Higher graphite content is considered to provide more cathodes, it accelerates the corrosion of the iron element in the rotor. There is no reliable correlation between the pearlite and ferrite of the gray cast iron rotor stiction force. The poor correlation between stiction force and microstructure also shows that the size of stiction force is not determined by a single factor.

Friction interaction between brake materials see a rise in temperatures of over 1000 oC contributing to thermal fade of brakes and deterioration/cracking of rotors. Various microstructural features like graphite, ferrite and pearlite could influence the mechanical and thermal properties and related friction performance of the brake materials. Even more relevant impact on properties and friction performance of rotors can be expected after coatings or surface treatments. The primary purpose of this research is to identify the impact of microstructure and surface treatment on properties and friction performance of four types of pearlitic gray cast irons. The C30, C20 and FC150 rotors were surface treated by bombarding with heavy ions which diffused into cast iron and created a coating with different chemistry and properties when compared to the “non-treated” rotors. Complete chemical and material characterization of the brake rotors using optical emission spectrometer (OES), carbon-sulfur combustion analyzer, polarized light microscopy, density (analytical balance and Archimedes principle), Brinell hardness tester, laser flash apparatus, scanning electron microscopy, and energy dispersive X-ray microanalysis. The pearlitic gray cast iron rotors are typified by the presence of graphite, carbides, and inclusions in an almost fully pearlitic matrix with a minimum amount (2-4 vol.%) of “free” ferrite. Graphite can be further classified based on its morphology. The investigated cast irons contained two different graphite types: type VII-E5 for the F150 OEM rotor, and type VII-C5 characteristic for the ASTM A48 classes C30 and C20, as well as the “Japanese” JIS G5501 FC150 rotors. It was identified from the initial curve fitting models that the observed microstructural differences in individual cast iron types are responsible for the observed mechanical (density – decreases with increasing ferrite and decreasing pearlite contents; hardness – decreases with increasing ferrite contents) and thermal properties (increase with increasing ferrite and pearlite contents), and friction performance (increases with increasing ferrite and decreasing graphite contents) of the studied rotors. The applied surface treatment also contributed to the modification of the mechanical and thermal properties, as well as friction performance of the studied rotors. However, there were not enough statistically relevant models developed from the generated data, which could identify the combined influence of various microstructural features observed and applied surface treatment over the properties and friction performance of the studied rotors.

Os principais mecanismos de desgaste, presentes em discos de freio ventilados automotivos, foram determinados utilizando ensaios de bancada em dinamometro inercial. Foram medidas a temperatura, rugosidade, taxa de desgaste, tensões residuais, coeficiente de atrito e desempenho de frenagem. Foi analisado o tribocontato através de técnicas de microscopia eletrônica e ótica. / The main mechanims of wear, present in ventilated brake disc had been determined, when submited to the braking test in inertial dynamometric simulator. Were measured wear taxes, temperature, residual stresses, friction coeficient, topographic of relief and analised their tribographics.

Resumo: Nesse trabalho foram desenvolvidas três composições à base de Si3N4 com quantidades e tipos de aditivos diferentes, com objetivos de desenvolver cerâmicas densas de altas resistências, para posteriores testes como ferramentas de corte na usinagem de torneamento do ferro fundido cinzento, ferro fundido vermicular e a liga Ti-6Al-4V. As composições utilizaram aditivos Y2O3/Al2O3 (10%) e AlN/Y2O3 (15 e 20%), e foram sinterizadas pelo processo de sinterização normal. Em seguida foram caracterizadas quanto as propriedades físicas e mecânicas, apresentando bons resultados. Posteriormente a composição de melhores propriedades (SNYA20), foi transformada em inserto para usinagem de corte de acordo com a norma ISO 1832. Os testes de torneamento foram realizados no ferro fundido cinzento com variações de parâmentros, onde para Vc=300m/min, f=0,32mm/rot e ap=1,00mm, alcançou um comprimento de corte de 6533m, superior aos encontrados em literatura, com diminuição dos desgastes, para maiores Vc e ap. O torneamento da liga Ti-6Al-4V em alta velocidade (Vc=180m/min, f=0,10mm/rot e ap=0,50mm), alcançou comprimento de corte de Lc=466m, para um desgaste VBmax=2,20mm. No torneamento do ferro fundido vermicular, com variações de parâmetros, alcançou resultados superiores aos encontrados na literatura com ferramentas cerâmicas comercial, utilizando Vc=200mm/min, f=0,20mm/rot e ap= 0,50mm, obteve-se comprimento de corte Lc=1658m. Os resultados de usinagem obtidos nesse trabalho estão relacionados com as propriedades e fases obtidas. Entretanto alem dos resultados obtidos essas ferramentas apresentam custo em torno de 50% das comerciais e redução de 17- 20% de custo no processo, devido ao uso de fluido refrigerante e proteção ao meio ambiente. / Abstract: In this work three compositions to base Si3N4 with amounts and types of different additives had been developed, with objective to develop dense ceramics of high strength to possible test as cutting tools in turning of gray cast iron, compacted graphite iron and titanium alloy (Ti-6Al-4V). The compositions had used additives Y2O3/Al2O3 (10%) and AlN/Y2O3 (15 and 20%), and were sinterized by process normal sintering. After sintering the physical and mechanical properties had been characterized, showing interesting results. Posterior the composition the best properties (SNYA20), was transformed into cutting tools to machining in the stand norm ISO 1832. The turning tests had been carried in gray cast iron with different parameters, where to Vc=300m/min, f=0,32mm/rev and ap=1,00mm, obtained a cut length of 6533m, achieving value superior at found in literature, with important reduction to larger cutting speed and cut depth. The turning of the Ti-6Al-4V alloy in high cutting speed (Vc=180m/min, f=0,10mm/rev and ap=0,50mm), obtained cutting length of Lc=466m, to VBmax=2,20mm. In turning compacted graphite iron, with different parameters, obtained value superior at found in literature, when utilize cutting tools ceramics of commercial materials, using for this Vc=200mm/min, f=0,20mm/rev and ap = 0,50mm. These condition obtained cut length of Lc=1658m. The results achieved in this work have been associated with the important physical and mechanical proprieties and phase of cutting tools. However the results obtained with these cutting tools present lower cost (50%) when compared with commercial cutting tools of similar material e reduction of cost in around 17-20%, because the do not use coolant, beside of protection at environment. / Orientador: Sérgio João Crnkovic / Coorientador: Olivério Moreira de Macedo Silva / Doutor

Os principais mecanismos de desgaste, presentes em discos de freio ventilados automotivos, foram determinados utilizando ensaios de bancada em dinamometro inercial. Foram medidas a temperatura, rugosidade, taxa de desgaste, tensões residuais, coeficiente de atrito e desempenho de frenagem. Foi analisado o tribocontato através de técnicas de microscopia eletrônica e ótica. / The main mechanims of wear, present in ventilated brake disc had been determined, when submited to the braking test in inertial dynamometric simulator. Were measured wear taxes, temperature, residual stresses, friction coeficient, topographic of relief and analised their tribographics.

Orientador: Anselmo Eduardo Diniz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-19T10:37:14Z (GMT). No. of bitstreams: 1 MunozDias_LuizRoberto_M.pdf: 3936007 bytes, checksum: fb9f262c5583315e04e019d84e27c1c1 (MD5) Previous issue date: 2011 / Resumo: Os ferros fundidos cinzentos são muito empregados em diversos segmentos da indústria, sendo sua utilização preferida para composição de bases de máquinas por ter baixo custo de aquisição, alta capacidade de amortecimento a vibrações e facilidade de fabricação. As normas que norteiam a produção destas ligas determinam as classes divididas por faixas de resistência à tração e forma da grafita presente na estrutura. A classe GG-25, determina resistência à tração situada entre 250Kgf/mm² e 300Kgf/mm² e forma de grafita lamelar. Esta pesquisa tem como objetivo investigar a diferença de usinabilidade entre ferros fundidos cinzentos desta mesma classe, ou seja, dentro da tolerância da norma, com diferentes concentrações de perlita e ferrita. Avaliou-se a usinabilidade em termos de vida de ferramenta, esforços de corte e rugosidade em operações de fresamento em acabamento com ferramentas de metal duro e cerâmica (com geometrias de corte idênticas) e diferentes velocidades de corte em um material contendo 100% de perlita e em outro com 50% de perlita. Os resultados mostraram que os lotes perlíticos, em função de resistência e dureza maiores, provocam desgaste das ferramentas mais rapidamente que os lotes 50% perlíticos e também consomem maiores esforços de corte. Também foi possível notar que as ferramentas de cerâmica apresentaram vida maior que as ferramentas de metal duro. Os mecanismos causadores de desgastes da ferramenta foram: difusão, adesão de ferro com conseqüente remoção de partículas (attrition) e trincas térmicas / Abstract: The gray cast irons are frequently used in various fields of industry, mainly for machine bed due to the low cost, high vibration damping capacity and easiness of manufacturing. The standards that guide the production of these alloys determine the classes based on the range of tensile strength and shape of graphite in the structure. The class GG-25 determines the tensile strength between 250Kgf/mm² and 300Kgf/mm2 and lamellar shape of graphite flakes. This research aims at investigate the difference of machinability between two gray cast irons belonging to the same class, i.e., within tolerance of the standard, with different pearlitic / ferritic concentrations. Machinability was evaluated in terms of tool life, cutting forces and workpiece surface roughness in finish milling with carbide and ceramic tools (with similar cutting geometries) and different cutting in a material containing 100% pearlite and another with 50% pearlite. The results showed that in the milling of the pearlitic alloy, due to higher strength and hardness, tool wear progressed faster than in the milling of ferritic alloy and also consumed higher cutting forces. It was also possible to note that ceramic tools showed longer life than carbide tools. The main observed mechanisms of wear were diffusion, adhesion of iron with consequent removal of tool material (attrition) and thermal cracks. / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Cylinder liners in heavy-duty truck engines are subjected to intense vibrations and may sustain damage from the cavitation of bubbles in the coolant liquid, with some risks of leakage and engine breakdown. An ultrasonic oscillating probe was used to simulate the pitting rates and behavior of samples extracted from cylinder liners, which are made of grey cast iron, with differences in surface roughness, glycol and inhibitor content in coolant, coolant temperature and graphite flake class; bainitic microstructures were also tested. Measurements consisted of mass losses under set intervals during experiments lasting 2.5 or 4 hours. Affected surfaces were later evaluated with scanning electron microscopy and confocal microscopy. Results indicate higher cavitation damage with: lower concentrations of glycol and absence of corrosion/cavitation inhibitors in the coolant liquid, lower liquid temperatures between 76⁰C and 90⁰C, and presence of B-type graphite class in the microstructure. Results regarding surface roughness were inconclusive. A sequence of surface damage mechanisms has been proposed, with corresponding microscope observations, to explain the mass loss trends and the associated microstructural changes over time.

Helical heating coils are widely used in most conventional electric stoves for many years, these heating coils can reach 600-700°C, which is higher than the ignition point of oil and grease (about 400°C), leading to many fires. Pioneering Technology Inc. has developed a Safe-T Element plate to address such problem. The Safe-T Element plate is manufactured from Gray Cast Iron. However, these plates deform during its use. This study was carried out to investigate the current Safe-T Element design, both experimentally and numerically, in order to determine the root causes behind the deformation problem of the plate, and to suggest changes to the existing design in order to limit its distortion to acceptable targets. A chemical analysis was carried out to establish the type of material of the Safe-T Element plate. Chemical analysis showed that the material of the plate is cast iron. The microstructure of the plate was tested in order to examine its type and homogeneity. Tensile testing was carried to establish the grade of the material, and to calculate the value of its young's modulus and yield strength. Tensile testing indicated that the material of the Safe-T Element plate is close to Gray Cast Iron Class 40. Differential scanning calorimetry testing was carried out to investigate thermal stability of the plate material. This test indicated that material is thermally stable. Thermal cycling testing indicated that the root cause of the deformation problem is elastic thermal buckling. Temperature uniformity tests were carried out. More than 100°C temperature variation in the radial direction was observed. To address the distortion of the plate, an optimum geometry has been suggested based on the findings of the numerical investigation by removing the outer ring from the original design of the plate. / Thesis / Master of Applied Science (MASc)

Uma parte significativa das perdas por atrito num motor automotivo resulta da ação de partículas abrasivas. Dentre as fontes possíveis, podem ser citados o próprio meio ambiente - partículas que passam pelo filtro de ar - o desgaste de partes metálicas do motor ou mesmo resíduos de combustão. Essas partículas podem ficar encrustadas em anéis do pistão, ou ficar na interface entre pistão e bloco ou camisa, e são responsáveis por sulcos axiais, na direção do movimento do pistão, observáveis em motores usados. O objetivo deste trabalho foi obter um melhor entendimento dos mecanismos de desgaste relacionados com o sulcamento de camisa/bloco e identificar conjuntos de testes laboratoriais capazes de reproduzi-los sob condições controladas. Amostras de ferro fundido cinzento (FoFo) e de aço AISI 1070 com dureza de matriz próxima daquela encontrada em FoFo (?200HV30) foram submetidas a ensaios de riscamento em tribômetros. Verificou-se que riscos executados com um endentador cônico submetido a cargas na faixa de 20 a 50 mN eram similares aos sulcos observados em camisas ou blocos. Ensaios com outros materiais, como alumínio e latão e mesmo aço de diferentes durezas contribuíram para melhorar o entendimento dos resultados. Não foi observada transição brusca entre mecanismos de abrasão. O cálculo do fator de remoção de material, fab, a partir de perfilometria óptica resultou em valores com dispersão elevada; não foi possível associa-los aos diferentes mecanismos de abrasão observados. Valores obtidos para o coeficiente de atrito no riscamento permitiram fazer uma estimativa inicial de energia gasta nos processos abrasivos do motor. / A significant part of the friction losses in an automotive engine results from the abrasive action of particles. Among possible sources of such particles one can mention the environment - particles that were not retained by the filters - metallic residues from worn parts or even combustion residues. They may be picked up by piston rings and become part of their surfaces or stay loose in the piston/liner interface. Those particles are responsible for axial grooves that are observed in the liners of used engines. The objective of this work was to get a better understanding of the wear mechanisms related to liner/bore grooving and to identify a laboratory testing setup that might reproduce them under controlled conditions. Specimens of Gray Cast Iron (GCI) and of AISI 1070 steel with matrix hardness close to that found in GCI (?200HV30) were submitted to scratch tests in a tribometer. It was found that scratches performed under 20-50 mN indenter load (conical tip) were similar to grooves observed in cylinder liners. Tests with other materials such as aluminum, brass and even steel with different hardness values contributed to a better understanding of the results. No sharp transition between abrasion mechanisms was observed. Calculation of material removal factor fab from optical profilometry resulted in values with a large dispersion; they could not be associated with different abrasion mechanisms. Friction coefficient values obtained from the tests were used to make preliminary estimates of energy consumption due to abrasive processes in the engine.