The present work was performed at AB Sandvik Coromant as a part in improving the knowledge and understanding about wear of uncoated WC/Co cutting tools during turning of titanium alloy Ti-6Al-4V. When machining titanium alloys, or any other material, wear of the cutting tools has a huge impact on the ability to shape the material as well as the manufacturing cost of the finished product. Due to the low thermal conductivity of titanium, high cutting temperatures will occur in narrow regions near the cutting edge during machining. This will result in high reaction and diffusion rates, resulting in high cutting tool wear rates. To be able to improve titanium machining, better knowledge and understanding about wear during these tough conditions are needed. Wear tests were performed during orthogonal turning of titanium alloy and the cutting tool inserts were analysed by SEM, EDS and optical imaging in Alicona InfiniteFocus. Simulations in AdvantEdge provided calculated values for cutting temperatures, cutting forces and contact stresses for the same conditions as used during wear tests. It was found that turning titanium alloy with WC/Co cutting tools at cutting speeds 30-60 m/min causes chamfering of the cutting tool edge and adhesion of a build-up layer (BUL) of workpiece material on top of the rake face wear land. The wear rate for these low cutting speeds was found to be almost unchanging during cutting times up to 3 minutes. During cutting speeds of 90-115 m/min, crater wear was found to be the dominating wear mechanism and the wear rate was found to have a linear dependence of cutting speed. An Arrhenius-type temperature dependent wear mechanism was found for high cutting speeds, between 90 and 115 m/min.

Launchers are military systems that are responsible for communication with munitions, safe seperation and aiming of rockets and missiles to the target. Since they are military equipments, they are used in harsh environments. One of the most important design considerations for military equipment is its maintability and one of the most important parameter which affects the maintability is wear in launchers. Therefore, for predicting the life-time of a launcher, wear should be investigated beside other parameters such as fatigue etc. This thesis study includes experimental and modeling study about dry sliding wear in some mechanical parts of a typical rail launcher that is used in helicopters. Firstly, measurements about the material loss, which is generated during firing of missiles, were made on launcher components which have interfaces with missile. Then, these results were used to simulate the wear phenomenon by using a commercial finite element program, ANSYS. By the help of finite element model, crack initiation period depending on wear is tried to be evaluated without making additional firing tests.

Titanium carbide (TiC) and titanium carbonitride (Ti(C,N)) are both common components in hard, wear resistant ceramic-metal composites, or cermets. In this study the intermetallic nickel aluminide (Ni3Al) has been used as a binder for the production of TiC and Ti(C,N) based cermets. These cermets offer several improved characteristics relative to conventional WC-based ‘hardmetals’, such as lower mass and improved oxidation resistance, which are also combined with high fracture resistance, hardness and wear resistance. The cermets were produced using an in-situ, reaction sintering procedure to form the stoichiometric Ni3Al binder, with the binder contents varied from 20 to 40 vol%. However, for high N content Ti(C,N) cermets, the wettability of molten Ni3Al is relatively poor, which leads to materials with residual porosity. Therefore various amounts of Mo2C (1.25, 2.5, 5 and 10 vol%) were incorporated into the Ti(C0.3,N0.7)-Ni3Al cermets, with the aim of improving the densification behaviour. Mo2C was found to improve upon the wettability during sintering, thus enhancing the densification, especially at the lower binder contents. The tribological behaviour of TiC and Ti(C,N) cermets have been evaluated under reciprocating sliding conditions. The wear tests were conducted using a ball-on-flat sliding geometry, with a WC-Co sphere as the counter-face material, for loads from 20 to 60 N. The wear response was characterised using a combination of scanning electron microscopy, energy dispersive X-ray spectroscopy, and focused ion beam microscopy. Initially, two-body abrasive wear was observed to occur, which transitions to three-body abrasion through the generation of debris from the cermet and counter-face materials. Ultimately, this wear debris is incorporated into a thin tribolayer within the wear track, which indicates a further transition to an adhesive wear mechanism. It was found that Mo2C additions had a positive effect on both the hardness and indentation fracture resistance of the samples, but had a detrimental effect on the sliding wear response of the cermets. This behaviour was attributed to increased microstructural inhomogeneity with Mo2C additions.

Titanium carbonitride (Ti(C,N)) cermets have become more popular in recent research due to their mix of high hardness, high hot hardness, good ductility, chemical stability, and low densities. These mechanical properties make Ti(C,N)-cermets especially desirable as a replacement for current ‘hardmetals’, such as tungsten carbide cobalt (WCCo), as it is known that WC-Co exhibits poor mechanical behaviour at elevated temperatures. Additional interest and research has been conducted in reference to binders which enhance the cermet’s capability to retain strength at high temperatures while remaining ductile. One such binder, Ni3Al actually increases in yield strength up to a temperature of ~900°C. In this thesis, the production method utilizing melt infiltration for TiC, Ti(C0.7,N0.3), Ti(C0.5,N0.5), and Ti(C0.3,N0.7)-based cermets with Ni3Al binder contents of 20, 30 and 40 vol. % have successfully been developed and utilized. This process produced high density samples at each nitrogen content for all binder contents, excluding Ti(C0.3,N0.7). Ti(C0.3,N0.7)-Ni3Al samples at 20 and 30 vol. % suffered from poor infiltration and could not be tested. The reciprocating wear mechanisms were examined, using a ball-on-flat test, utilizing WC-Co spheres with a diameter of 6.35 mm as a counter-face, and test parameters of 20 Hz, 2 hrs., and applied loads of 20, 40, 60 and 80 N. The wear tracks were examined using optical profilometry, SEM, and EDS to determine the volumetric wear rate, and the dominant wear mechanisms. The wear volume, and wear mechanisms were compared with the effect of binder content, nitrogen content, and applied load.

Os aços Hardox possuem microestrutura de martensita revenida e são caracterizados pelas elevadas dureza e resistência à tração, sendo empregados em situações que requerem alta resistência ao desgaste. Entretanto, os processos de soldagem alteram significativamente a sua microestrutura e propriedades. Assim, o objetivo deste estudo foi avaliar a resistência ao desgaste de juntas soldadas de um aço Hardox 500 produzidas através do processo MAG convencional e, juntamente, com o Hardox sem soldagem (metal base), para comparação. A soldagem ocorreu utilizando dois consumíveis, um recomendado pela empresa fabricante do aço, o AWS ER80S-G, e outro de maior resistência mecânica, o consumível AWS ER120SG. As propriedades mecânicas das juntas soldadas foram avaliadas através de perfis de microdureza, ensaios de tração e dobramento. Ainda, foi realizada uma análise da superfície de fratura dos corpos de prova do ensaio de tração, em microscópio eletrônico de varredura. Foram executados ensaios de desgaste por um abrasômetro do tipo roda de borracha. Análises através de microscopia óptica e microscopia eletrônica de varredura foram utilizadas para verificar os mecanismos de desgaste nas superfícies submetidas à abrasão Nos ensaios de dobramento, constatou-se que a condição soldada com o arame de menor resistência apresentou maior ductilidade. Verificou-se, também, que com a soldagem houve uma diminuição da resistência mecânica das juntas em comparação ao metal sem soldagem. Em relação aos ensaios de desgaste, com o uso do arame de maior resistência foi atingido um melhor desempenho no desgaste abrasivo em comparação ao de menor resistência, pois as taxas de desgaste foram de 0,058 e 0,083 mm³/m, respectivamente, mas o comportamento foi ainda inferior ao exibido pelo aço Hardox 500 sem soldagem, que apresentou uma taxa de desgaste de 0,031 mm³/m. Constatou-se, também, que os mecanismos de desgaste foram dúcteis em todas as condições estudadas, pois as superfícies desgastadas mostravam predominantemente micro sulcamento e regiões com micro fadiga; essa última parece ter aumentado de tamanho à medida que a dureza do material testado aumentava. / The Hardox steels have a martensite microstructure and are characterized by high hardness and tensile strength. This steel has been used in situations that require high resistance to wear. However, the welding processes significantly alter their microstructures and properties. Thus, the purpose of this study was to evaluate the wear resistance of welded joints of Hardox 500 steel produced by the conventional MAG process and with Hardox without welding (base metal), for comparison. The welding took place using two consumables, one recommended by the steel manufacturer, the AWS ER80S-G and another with higher resistance, the consumable AWS ER120S-G. The mechanical properties of welded joints were evaluated through micro hardness profiles, tensile and bending tests. In addition an analysis of the fracture surface of the tensile test specimen was carried out by scanning electron microscopy. Wear tests were performed by a rubber wheel type abrasometer. Analyses by optical microscopy and scanning electron microscopy were used to verify the mechanisms of wear on surfaces subjected to abrasion In the bending tests, it was verified that the welded condition with the filler metal of lower resistance presented greater ductility. It was also verified that with the welding, there was a decrease in the mechanical strength of the joints in comparison with the base metal. In relation to the wear tests, with the use of the higher strength wire, a better performance was obtained when compared to the lower one, since the wear rates were 0.058 and 0.083 mm³/m respectively, but the behavior was lower in the Hardox 500 steel without welding, which presented a wear rate of 0.031 mm³/m. It was also observed that the wear mechanisms were ductile in all the studied conditions, since the worn surfaces showed predominantly micro plowing and regions with micro fatigue, the latter seem to have increased in size as the hardness of the tested material increased.

abstract: The demand for miniaturized components with feature sizes as small as tens of microns and tolerances as small as 0.1 microns is on the rise in the fields of aerospace, electronics, optics and biomedical engineering. Micromilling has proven to be a process capable of generating the required accuracy for these features and is an alternative to various non-mechanical micro-manufacturing processes which are limited in terms of cost and productivity, especially at the micro-meso scale. The micromilling process is on the surface, a miniaturized version of conventional milling, hence inheriting its benefits. However, the reduction in scale by a few magnitudes makes the process peculiar and unique; and the macro-scale theories have failed to successfully explain the micromilling process and its machining parameters. One such characteristic is the unpredictable nature of tool wear and breakage. There is a large cost benefit that can be realized by improving tool life. Workpiece rejection can also be reduced by successfully monitoring the condition of the tool to avoid issues. Many researchers have developed Tool Condition Monitoring and Tool Wear Modeling systems to address the issue of tool wear, and to obtain new knowledge. In this research, a tool wear modeling effort is undertaken with a new approach. A new tool wear signature is used for real-time data collection and modeling of tool wear. A theoretical correlation between the number of metal chips produced during machining and the condition of the tool is introduced. Experimentally, it is found that the number of chips produced drops with respect to the feedrate of the cutting process i.e. when the uncut chip thickness is below the theoretical minimum chip thickness. / Dissertation/Thesis / Masters Thesis Engineering 2015

Os aços Hardox possuem microestrutura de martensita revenida e são caracterizados pelas elevadas dureza e resistência à tração, sendo empregados em situações que requerem alta resistência ao desgaste. Entretanto, os processos de soldagem alteram significativamente a sua microestrutura e propriedades. Assim, o objetivo deste estudo foi avaliar a resistência ao desgaste de juntas soldadas de um aço Hardox 500 produzidas através do processo MAG convencional e, juntamente, com o Hardox sem soldagem (metal base), para comparação. A soldagem ocorreu utilizando dois consumíveis, um recomendado pela empresa fabricante do aço, o AWS ER80S-G, e outro de maior resistência mecânica, o consumível AWS ER120SG. As propriedades mecânicas das juntas soldadas foram avaliadas através de perfis de microdureza, ensaios de tração e dobramento. Ainda, foi realizada uma análise da superfície de fratura dos corpos de prova do ensaio de tração, em microscópio eletrônico de varredura. Foram executados ensaios de desgaste por um abrasômetro do tipo roda de borracha. Análises através de microscopia óptica e microscopia eletrônica de varredura foram utilizadas para verificar os mecanismos de desgaste nas superfícies submetidas à abrasão Nos ensaios de dobramento, constatou-se que a condição soldada com o arame de menor resistência apresentou maior ductilidade. Verificou-se, também, que com a soldagem houve uma diminuição da resistência mecânica das juntas em comparação ao metal sem soldagem. Em relação aos ensaios de desgaste, com o uso do arame de maior resistência foi atingido um melhor desempenho no desgaste abrasivo em comparação ao de menor resistência, pois as taxas de desgaste foram de 0,058 e 0,083 mm³/m, respectivamente, mas o comportamento foi ainda inferior ao exibido pelo aço Hardox 500 sem soldagem, que apresentou uma taxa de desgaste de 0,031 mm³/m. Constatou-se, também, que os mecanismos de desgaste foram dúcteis em todas as condições estudadas, pois as superfícies desgastadas mostravam predominantemente micro sulcamento e regiões com micro fadiga; essa última parece ter aumentado de tamanho à medida que a dureza do material testado aumentava. / The Hardox steels have a martensite microstructure and are characterized by high hardness and tensile strength. This steel has been used in situations that require high resistance to wear. However, the welding processes significantly alter their microstructures and properties. Thus, the purpose of this study was to evaluate the wear resistance of welded joints of Hardox 500 steel produced by the conventional MAG process and with Hardox without welding (base metal), for comparison. The welding took place using two consumables, one recommended by the steel manufacturer, the AWS ER80S-G and another with higher resistance, the consumable AWS ER120S-G. The mechanical properties of welded joints were evaluated through micro hardness profiles, tensile and bending tests. In addition an analysis of the fracture surface of the tensile test specimen was carried out by scanning electron microscopy. Wear tests were performed by a rubber wheel type abrasometer. Analyses by optical microscopy and scanning electron microscopy were used to verify the mechanisms of wear on surfaces subjected to abrasion In the bending tests, it was verified that the welded condition with the filler metal of lower resistance presented greater ductility. It was also verified that with the welding, there was a decrease in the mechanical strength of the joints in comparison with the base metal. In relation to the wear tests, with the use of the higher strength wire, a better performance was obtained when compared to the lower one, since the wear rates were 0.058 and 0.083 mm³/m respectively, but the behavior was lower in the Hardox 500 steel without welding, which presented a wear rate of 0.031 mm³/m. It was also observed that the wear mechanisms were ductile in all the studied conditions, since the worn surfaces showed predominantly micro plowing and regions with micro fatigue, the latter seem to have increased in size as the hardness of the tested material increased.

Um dos principais problemas dos materiais restauradores (incluindo a resina composta) é o desgaste por abrasão. Portanto, o objetivo neste trabalho foi avaliar in vitro o desgaste abrasivo por escovação da resina composta 4Seasons, de duas cores diferentes (A3 e C4) e com fotopolimerização por dois diferentes tempos (20 e 40 s), utilizando escova Sorriso, da Colgate, e creme dentifrício Colgate Tripla Ação; também foi usado, como material de referência, o polimetil metacrilato. Assim, foram confeccionados dez corpos-de-prova, para cada um dos cinco grupos formados (PMMA, A3 20s, A3 40s, C4 20s, C4 40s). Cada espécime consistia basicamente num cilindro de cerca de 1,8 mm de altura e 8 mm de diâmetro. Cada espécime, após sua confecção, era imerso em água deionizada, a 37 ± 2 ºC, por 24 horas, quando então eram regularizados com lixa (granulação # 600 e # 1.000); após lavagem com ultrassom, voltavam a ser armazenados nas mesmas condições, até completar-se um período de uma semana. A escovação foi então efetuada numa máquina própria, que comportava dez espécimes simultaneamente, sendo de 3 N a carga de cada escova sobre o respectivo espécime; a velocidade de cada escova era de 18 cm/s, com a freqüência (ida e volta, num percurso total de 4 cm) de 4,5 ciclos/s; o período de escovação de um espécime compreendia 150. 000 ciclos. Foram efetuados cinco períodos (ou lotes) de escovação, de modo que um espécime do material de cada grupo tivesse sido submetido à ação de cada uma das posições ocupadas pelas dez escovas. A quantidade de massa perdida, para cada espécime, foi calculada por meio de pesagem (pré e pós escovação), numa balança com acuidade de milionésimo de grama. O trabalho foi também ilustrado com gráficos de rugosidade e com fotomicrografias tomadas ao MEV. A taxa média de desgaste foi de 2,8 mg para o PMMA, de 5,5 mg para o A3-20s, 4,7 mg para o A3-40 s, 5,4 para o C4-20s e 4,2 mg para o C4-40s; a respectiva análise de variância mostrou não existir diferença significante entre os grupos, para p=0,166; o coeficiente de variação entre os grupos foi bastante semelhante. Foi possível concluir que não existiu diferença da resistência ao desgaste abrasivo entre os grupos estudados. / One of the main problems of dental restorative materials (including the resin composites) is the abrasion wear. Therefore, the aim of this work was to evaluate in vitro the abrasive wear by toothbrushing of the resin composite 4Seasons, of two different colors (A3 and C4), cured by two different times (20 and 40 s), using a toothbrush (Sorriso - Colgate), and a dentifrice (Tripla Ação Colgate). Polimetil meth-acrylate was used as reference material. Ten cylindric samples (approximately 1.8 mm height and 8 mm diameter) had been prepared for each one of the five evaluated groups (PMMA, A3 20s, A3 40s, C4 20s, C4 40s). After confection, samples were immersed in deionized water, at 37 ± 2ºC, for 24 h, and then regularized by abrasive gritting with sandpaper (from #600 to # 1 000); after that, were cleaned in ultrasound bath, and restored to the same described conditions, until completing the period of one week. The toothbrushing was then conducted in a proper machine that holds 10 specimens simultaneously, with a 3 N load of each toothbrush on the respective sample. The speed of each toothbrush was of 18 cm/s, at a frequency of 4.5 cycles/s (each cycle consisting of 2 cm forward and 2 cm backward). 150. 000 cycles were applied per sample. Five periods (or lots) of toothbrushing had been performed, in a way that one sample of each group had been submitted to the brushing action at one position in the machine. The amount of weight loss for each sample was calculated by means of weighting (before and after toothbrushing), in an analytical balance with accuracy of millionth of gram. Roughness and MEV photomicrographies were also evaluated. The average rate of wear was of 2.8 mg for PMMA, 5.5 mg for A3-20s, 4.7 mg for A3-40 s, 5.4 for C4-20s, and 4,2 mg for C4-40s. One-way ANOVA showed no significant difference between groups (p = 0.166). The coefficient of variation between the groups was sufficiently similar. It was possible to conclude that difference of the resistance to the abrasive wear between the studied groups did not exist.

Este trabalho dedica-se ao estudo dos mecanismos de desgaste de ferramentas utilizadas em processos de conformação a frio, como punções e matrizes. O texto se inicia por uma discussão que há na literatura a respeito do esfolamento (tradução da palavra galling) que é o principal ao mecanismo de desgaste encontrado na conformação a frio. Em seguida apresenta-se uma breve análise do desempenho tribológico de punções usados industrialmente em operações de estampagem. Tornos CNC foram utilizados para a realização de alguns ensaios de desgaste por deslizamento, sem repetição de trilha, com materiais normalmente utilizados em conformação a frio. Ferramentas de aço AISI M2 com e sem revestimentos por filmes finos de TiN e AlTiCrN foram deslizadas contra aços AISI 1045. Resultados de força de atrito e observações das superfícies via microscopia foram obtidos para qualificar as diferentes condições ensaiadas. Ambas as condições de ferramentas revestidas apresentaram desempenho tribológico superior à ferramenta sem revestimento e uma inversão de desempenho foi observada entre as ferramentas revestidas: a ferramenta revestida com o filme de AlTiCrN apresentou um melhor desempenho quando a situação de ensaio foi mais branda. Quando os esforços foram mais severos, o melhor desempenho foi obtido com o revestimento de TiN. A essa inversão de desempenho foi atribuído o acabamento superficial dos filmes finos. / This work is devoted to the study of wear mechanisms in cold forming tools, such as punches and dies. The text begins with a discussion on the galling phenomenon, which is the main wear mechanism that takes place in cold forming operations. A brief analysis of the tribological behavior of punches that have operated in industrial conditions is then presented. Tests of sliding wear without repetition of the wear track were conducted in CNC lathes, considering the contact of materials normally used in cold forming operations. AISI M2 tool steels with and without TiN and AlTiCrN coatings were slided against AISI 1045 steel. Friction force results and microscopic surface observations were analyzed in order to qualify different tests conditions. Both coated tools conditions presented a better tribology performance than the uncoated ones and an inversion in performance was observed between the coated tools: the AlTiCrN coated tool had a better performance in milder conditions, while the TiN coated tool presented a better performance in more severe conditions. This inversion in performance was attributed to the surface finish of the coatings.

Orientador: Amauri Hassui / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-19T21:26:46Z (GMT). No. of bitstreams: 1 Therezani_DouglasFellipe_M.pdf: 8921001 bytes, checksum: 07f18992fbada55cf604b764eaafe4f8 (MD5) Previous issue date: 2012 / Resumo: A super liga Inconel 713C é uma liga cujo principal elemento de sua composição é o Níquel. A combinação do alto teor deste elemento mais a estrutura desse material faz com que ele seja muito difícil de ser usinado. Devido a esta dificuldade e carência de informações a respeito da usinagem desse material, o objetivo deste trabalho foi buscar uma combinação de ferramenta e parâmetros de corte que apresentassem uma vida da ferramenta em torno de 15 minutos, valor considerado viável economicamente pela prática industrial. Para isso foram testadas ferramentas de metal duro com duas geometrias diferentes, quatro tipos de revestimentos (TiAlN, TiAlN-TiN, TiCN-Al2O3-TiN e Al2O3) além da ferramenta de metal duro sem revestimento. Foram testadas também ferramentas cerâmicas (Al2O3 (pura), Si3N4 (sialon), Al2O3+SiCw (whiskers)) e de CBN. Dentre os ensaios realizados, a ferramenta de metal duro com a geometria CNMX e revestimento TiAlN apresentou uma taxa de desgaste menor que as demais testadas com uma vida de aproximadamente 17 minutos de corte / Abstract: The super alloy Inconel 713C is an alloy whose main element of its composition is nickel. The combination of high levels of this element and the structure of this material makes it very difficult to be transformed by the machining process. Because of this difficulty and lack of information about the machining of this material, the purpose of this study was to find a combination of tool and cutting parameters to present a tool life of around 15 minutes, which is considered economically viable for industrial practice. To achieve this purpose it was tested cemented carbide tools with two different geometries, four types of coatings (TiAlN, TiN, TiAlN, TiCN-Al2O3-TiN and Al2O3) in addition to the carbide tool without coating were tested. Tools were also tested ceramics (Al2O3 (pure), Si3N4 (sialon) + Al2O3 SiCw (whiskers)) and CBN. Among the tests, the carbide tool geometry CNMX and coating TiAlN presented a lower wear rate than the others tested with a life of approximately 17 minutes of cutting / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica