The availability of sophisticated machine tools, together with advanced cutting tool designs and high performance coatings has allowed machining to meet many challenges. A significant remaining challenge is the competitive milling of hardened steels at moderate to high cutting speeds. This is of particular importance for the die and mould making industry. Despite the necessity to achieve higher production rates and improved surface finish, cutting speeds above the range of 300-600 m/min are still not possible. This limitation is due to the combination of high mechanical, thermal and chemical interactions that are taking place on the tool surface during cutting. To address this situation, an extensive amount of research has been focused on developments associated with hard coatings such as nano-multilayered hard PVD coatings that exhibit novel mechanical and thermal properties. The development of methodologies for designing a cutting tool with a strong cutting edge micro-geometry has set guidelines for selecting proper cutting edge preparation for specific cutting applications. The results indicate that, the development of new hard coating designs is the most effective way to improve the service life of coated carbide tools for hard high speed milling applications. The developments of both robust and rigid substrate designs with adaptive cutting edge micro-geometries assist the cutting tool performance by favoring the surface adaptability of the deposited coating. The developments of different strategies for dry air cooling that provide a "soft-cool" environment seem to have a beneficial impact on cutting performance and tool life improvement. Dry air cooling is found to be more effective than chilled-air cooling and minimum-quantity-lubrication (MQL). Therefore, the utilization of a cutting environment tailored to meet the requirements of both the tool and the coating while providing sufficient air flow to remove chips from the cutting zone will complement the adaptability of the whole tool-workpiece-chip system. / Thesis / Master of Applied Science (MASc)

Há alguns anos, diversos estudos da influência dos parâmetros do tratamento térmico vêm sendo desenvolvidos, para a obtenção de propriedades que permitam atingir os requisitos de trabalho e que gerem ferramentas de vida útil estendida. Nesse contexto, tem sido demonstrado que o tratamento criogênico não só provoca a transformação da austenita residual, trazendo melhorias no dimensional da ferramenta, mas também pode promover a precipitação de carbonetos finos, com ganho em tenacidade e propriedades de desgaste.Neste estudo são relatados os resultados obtidos de ensaios de dureza, desgaste, impacto Charpy e microscopia TEM, efetuado em amostras de aço H13.Os tratamentos térmicos foram realizados em forno a vácuo com resfriamento por nitrogênio sob 5 bar de pressão, sendo utilizados os seguintes parâmetros: austenitização1040ºC, têmpera, e revenimento a 540ºC. As amostras foram comparadas com a condição de base que passou por tratamento térmico convencional, as outras condições foram submetidas a um revenido alternado com o banho criogênico. Nas rotas criogênicas o tempo de encharque em nitrogênio líquido foi de 1, 24 e 48 horas. Uma análise desses resultados permitiu constatar que o tratamento criogênico melhora a resistência ao desgaste, e influencia levemente a dureza. / A few years ago, several studies of the influence of parameters heat treatment have been developed to obtain properties that could meet the job requirements and managing tools for extended life. In this context, it has been demonstrated that the cryogenic treatment not only causes the transformation of austenite residual, bringing improvements in dimensional tool, but also can promote the precipitation of fine carbides, and an increase in toughness and wear properties. In this study there are the results of the test of hardness, two body abrasion wear, Charpy impact followed by microscopy TEM analyses were performed in samples from H13 steel. The heat treatments were performed in a vacuum furnace with cooling by nitrogen under pressure of 5 bar, and used the following parameters: austenitizing 1040°C, quenching, and tempering at 540°C. The aim was compared the H13 performance under of conventional heat treatment and cryogenic bath after quenching and before tempering. Soaking times in the cryogenic temperature were: 1, 24, and 48 hours. Analyses this results has shown the heat treatment increased the wear resistance, and slightly affects the hardness.

Desde a década de 90 o fresamento HSM é um processo aplicado na fabricação de moldes e matrizes e, mais especificamente, no acabamento destes componentes. Segundo um levantamento realizado pelo LFS/USP, entre usuários de moldes e matrizes da região de São Paulo, foi confirmada a existência da dispersão da vida de matrizes e moldes. Assim, o objetivo deste trabalho é verificar se esta dispersão está relacionada com os efeitos da usinagem, ou seja, dos parâmetros de corte sobre o desempenho tribológico (vida da matriz). Para isso foi necessário determinar a influência dos parâmetros de corte nas características da integridade da superfície e, por sua vez, como estas características afetam o desempenho. As amostras do aço AISI H13 foram usinadas por fresamento HSM com métodos adotados na fabricação de matrizes e moldes. Os parâmetros de corte investigados foram: velocidade de corte (vc), profundidade de corte (ap), penetração de trabalho (ae) e avanço por dente (fz). As características da integridade da superfície medidas foram: parâmetros de rugosidade pelo método de perfilometria 3D, espessura da camada branca por microscopia óptica e eletrônica de varredura, microdureza da superfície e das subcamadas na seção transversal e tensão residual por difração de raios-x. Após a caracterização, as amostras foram submetidas ao desgaste por deslizamento em um tribômetro na configuração pino-placa com movimento alternado, sob as condições de contorno próximas do forjamento a frio (pressão de contato, material da peça, matriz, velocidade de deslizamento e lubrificante) para posterior correlação com os parâmetros de corte. Nesta etapa, o corpo é a amostra de aço AISI H13 ? 565 HV fresada pela HSM e, o contra-corpo é pino de aço AISI 1020. No âmbito das variáveis investigadas é proposto um modelo capaz de prever o desempenho em função das características topográficas (Str, Sq, índice de formação de cavidades - IFC) e da tensão residual. A camada branca intensamente investigada na literatura não apresentou influência devido a sua formação ocorrer no vale e não nos cumes onde ocorrem os contatos. / Since 90, the HSM milling process to manufacture dies and molds has been applied and, more specifically, in finishing operation those components. In according to LFS/USP survey, among São Paulo region dies and molds users, the dies and molds life dispersion has been confirmed. This dispersion can be related with machining effects on tribological performance and, therefore, on dies and molds life and has not be explained by scientific community yet. Thus, the objective of this work is to verify if this dispersion is related with cutting parameters effects on tribological performance. In order to do it was necessary to determine the cutting parameters influence on surface integrity characteristics and how this characteristic affects the performance. AISI H13 Steel samples were machined by HSM milling by using manufacturing dies and molds methods. The investigated cutting parameters were: cutting speed (vc), cutting depth (ap), working engagement (ae) and feed per tooth (fz). The surface integrity characteristics measured were: roughness parameters by 3D profilometer method, white layer thickness by optical and scanning electronic microscopy, surface and transversal sub-layers section microhardness and residual stresses by x-ray diffraction. Before characterization, the tribometer in pin-plate with alternate movement configuration was performed to sliding wear the samples nearly cold forging conditions, to posterior correlation with cutting parameters. In this stage, the body was the AISI H13? 565 HV steel HSM milling samples and, the counter-body was pin of AISI 1020 steel. In the investigated parameter ambit one model is proposed which is able to predict the performance in topography character functions (Str, Sq, cavity formation index - CFI) and residual stresses. The white layer, which was intensely investigated by other researchers, has no significant influence because its formation occurs in the valley and not at the summits where the contacts occur.

Desde a década de 90 o fresamento HSM é um processo aplicado na fabricação de moldes e matrizes e, mais especificamente, no acabamento destes componentes. Segundo um levantamento realizado pelo LFS/USP, entre usuários de moldes e matrizes da região de São Paulo, foi confirmada a existência da dispersão da vida de matrizes e moldes. Assim, o objetivo deste trabalho é verificar se esta dispersão está relacionada com os efeitos da usinagem, ou seja, dos parâmetros de corte sobre o desempenho tribológico (vida da matriz). Para isso foi necessário determinar a influência dos parâmetros de corte nas características da integridade da superfície e, por sua vez, como estas características afetam o desempenho. As amostras do aço AISI H13 foram usinadas por fresamento HSM com métodos adotados na fabricação de matrizes e moldes. Os parâmetros de corte investigados foram: velocidade de corte (vc), profundidade de corte (ap), penetração de trabalho (ae) e avanço por dente (fz). As características da integridade da superfície medidas foram: parâmetros de rugosidade pelo método de perfilometria 3D, espessura da camada branca por microscopia óptica e eletrônica de varredura, microdureza da superfície e das subcamadas na seção transversal e tensão residual por difração de raios-x. Após a caracterização, as amostras foram submetidas ao desgaste por deslizamento em um tribômetro na configuração pino-placa com movimento alternado, sob as condições de contorno próximas do forjamento a frio (pressão de contato, material da peça, matriz, velocidade de deslizamento e lubrificante) para posterior correlação com os parâmetros de corte. Nesta etapa, o corpo é a amostra de aço AISI H13 ? 565 HV fresada pela HSM e, o contra-corpo é pino de aço AISI 1020. No âmbito das variáveis investigadas é proposto um modelo capaz de prever o desempenho em função das características topográficas (Str, Sq, índice de formação de cavidades - IFC) e da tensão residual. A camada branca intensamente investigada na literatura não apresentou influência devido a sua formação ocorrer no vale e não nos cumes onde ocorrem os contatos. / Since 90, the HSM milling process to manufacture dies and molds has been applied and, more specifically, in finishing operation those components. In according to LFS/USP survey, among São Paulo region dies and molds users, the dies and molds life dispersion has been confirmed. This dispersion can be related with machining effects on tribological performance and, therefore, on dies and molds life and has not be explained by scientific community yet. Thus, the objective of this work is to verify if this dispersion is related with cutting parameters effects on tribological performance. In order to do it was necessary to determine the cutting parameters influence on surface integrity characteristics and how this characteristic affects the performance. AISI H13 Steel samples were machined by HSM milling by using manufacturing dies and molds methods. The investigated cutting parameters were: cutting speed (vc), cutting depth (ap), working engagement (ae) and feed per tooth (fz). The surface integrity characteristics measured were: roughness parameters by 3D profilometer method, white layer thickness by optical and scanning electronic microscopy, surface and transversal sub-layers section microhardness and residual stresses by x-ray diffraction. Before characterization, the tribometer in pin-plate with alternate movement configuration was performed to sliding wear the samples nearly cold forging conditions, to posterior correlation with cutting parameters. In this stage, the body was the AISI H13? 565 HV steel HSM milling samples and, the counter-body was pin of AISI 1020 steel. In the investigated parameter ambit one model is proposed which is able to predict the performance in topography character functions (Str, Sq, cavity formation index - CFI) and residual stresses. The white layer, which was intensely investigated by other researchers, has no significant influence because its formation occurs in the valley and not at the summits where the contacts occur.

Há alguns anos, diversos estudos da influência dos parâmetros do tratamento térmico vêm sendo desenvolvidos, para a obtenção de propriedades que permitam atingir os requisitos de trabalho e que gerem ferramentas de vida útil estendida. Nesse contexto, tem sido demonstrado que o tratamento criogênico não só provoca a transformação da austenita residual, trazendo melhorias no dimensional da ferramenta, mas também pode promover a precipitação de carbonetos finos, com ganho em tenacidade e propriedades de desgaste.Neste estudo são relatados os resultados obtidos de ensaios de dureza, desgaste, impacto Charpy e microscopia TEM, efetuado em amostras de aço H13.Os tratamentos térmicos foram realizados em forno a vácuo com resfriamento por nitrogênio sob 5 bar de pressão, sendo utilizados os seguintes parâmetros: austenitização1040ºC, têmpera, e revenimento a 540ºC. As amostras foram comparadas com a condição de base que passou por tratamento térmico convencional, as outras condições foram submetidas a um revenido alternado com o banho criogênico. Nas rotas criogênicas o tempo de encharque em nitrogênio líquido foi de 1, 24 e 48 horas. Uma análise desses resultados permitiu constatar que o tratamento criogênico melhora a resistência ao desgaste, e influencia levemente a dureza. / A few years ago, several studies of the influence of parameters heat treatment have been developed to obtain properties that could meet the job requirements and managing tools for extended life. In this context, it has been demonstrated that the cryogenic treatment not only causes the transformation of austenite residual, bringing improvements in dimensional tool, but also can promote the precipitation of fine carbides, and an increase in toughness and wear properties. In this study there are the results of the test of hardness, two body abrasion wear, Charpy impact followed by microscopy TEM analyses were performed in samples from H13 steel. The heat treatments were performed in a vacuum furnace with cooling by nitrogen under pressure of 5 bar, and used the following parameters: austenitizing 1040°C, quenching, and tempering at 540°C. The aim was compared the H13 performance under of conventional heat treatment and cryogenic bath after quenching and before tempering. Soaking times in the cryogenic temperature were: 1, 24, and 48 hours. Analyses this results has shown the heat treatment increased the wear resistance, and slightly affects the hardness.

A thermo-mechanical finite element model is developed to determine the temperature history and residual stresses in a Cu-H13 thin-walled plate deposited by the Laser Engineered Net Shaping (LENSTM) process. The same model is also applied to a H13-H13 sample to compare the results. The input laser power is adjusted to maintain a steady molten pool size and depth. For a constant scanning speed the laser power decreases with the addition of more layers, and with the increase of scanning speed the laser power needs to be increased. The Z-component of residual stresses is greater than the other components, and is compressive near the center of the wall and tensile at the free edges. The residual stress levels near the free edges are higher in the H13-H13 sample than in the Cu-H13 sample. In these regions, the use of unidirectional scanning results in a higher stress accumulation than the alternating scanning.

The recent development of prototyping systems which can produce patterns for investment casting with significant time reduction from traditional techniques, has raised interest in the use of casting as a method to produce tooling for downstream prototype testing. However, the accuracy of the casting process remains a major obstacle to the use of these tools. Simultaneous development of numerical modelling techniques suggest that it will be possible to predict casting contraction and distortion. If this were possible, corrections could be made before castings are produced, resulting in time and cost savings, as well as potential improvement in the accuracy. Before these models can be applied, there is a need for both material property data and experimental data with which to validate the numerical models. The aims of this work are to: 1) Develop further understanding of the processes in investment casting that contribute to the dimensional changes and variability. 2) Develop the required data for numerical modelling and apply this to simulate the dimensional changes in investment casting. An apparatus has been designed to measure the dimensional and thermal history of investment castings with displacement transducers and thermocouples. Casting dimensions were also accurately measured to determine the final contraction of nominally unconstrained and thermally constrained castings. Numerical simulations of the temperatures, stress and distortion were compared with the experimental results and provide a detailed explanation of the processes involved. Data for these simulations were developed using a combination of direct measurement and iterative inverse modelling.

No description available.

As a type of steel with notable resistance to thermal fatigue, cracking, and abrasion, AISI H13, is known for its machining ease, high hardness, and consistent heat treatment response. These qualities make AISI H13 a preferred choice for fabricating dies, moulds, and tools exposed to high temperatures, rendering it popular in metalworking. Enhanced cooling technology in die and casting moulds necessitates intricate geometries achievable through additive manufacturing (AM). To further advance part complexity and surface finish in inaccessible regions, the industry is increasingly adopting additive-subtractive hybrid manufacturing (ASHM), showing promising growth. There are, however, some concerns associated with this process, especially with the subtraction part, which is done through machining. These include the low machinability of the workpiece due to the higher hardness of additively manufactured parts compared to conventional methods. These issues are more pronounced in ASHM processes because liquid coolants or lubricants cannot be easily used, nor can the parts be heat-treated before machining. As a first step in this study, we performed a comprehensive literature review on solid lubricants used in machining so far. Their effectiveness, mechanisms, challenges, and recent developments were discussed in detail. The main purpose of this study was to introduce and investigate the effectiveness of our novel metallic solid lubricant coating for machining of AISI H13 additive manufactured parts in ASHM processes. Since the goal of this study was to mimic the ASHM process, the lubricant coating was used in dry machining, without the application of any liquid lubricant or coolant. Moreover, the workpiece was not heat treated and the tests were performed on an as-built additively manufactured AISI H13 part. A detailed study was performed to assess the impact of these lubricant coatings on AISI H13 surface integrity. The findings showed that the soft metallic lubricant coating considerably reduced the machining force and improved the surface roughness subsurface properties of the part. This method proved to be an effective solution for avoiding lubricants in ASHM processes, while significantly improving the machinability of AISI H13 parts in ASHM processes. / Thesis / Master of Applied Science (MASc) / AISI H13 tool steel is extensively utilized in tooling applications due to its exceptional wear resistance, toughness, and capability to maintain hardness at high temperatures, making it an asset for industrial uses, particularly in die and tooling manufacturing. One significant application is in the fabrication of conformal cooling channels, where additive manufacturing (AM) is the preferred method for creating intricate geometries. With the introduction of additive subtractive hybrid manufacturing (ASHM), there's an opportunity to enhance both the surface finish and the complexity of designs. However, ASHM introduces specific challenges, notably in machining. This study aims to tackle these challenges by focusing on a dry machining process for AISI H13, omitting the use of coolant and investigating the impact on surface integrity. By integrating a novel class of solid lubricant coating, the research seeks to bypass traditional methods, aiming for an improvement in machining outcomes. The results indicate that this new class of lubricant coating could significantly enhance the machining process, providing an exceptional alternative to conventional approaches and contributing to the advancement of manufacturing technologies.

Neste trabalho estudou-se o efeito do tratamento de boretação na resistência ao desgaste, corrosão e oxidação dos aços AISI 1060 e AISI H13. As amostras dos aços foram boretadas com pó a 900 e 1000°C por 2 e 4 horas. Foram realizados ensaios de microdesgaste em máquina do tipo esfera fixa, sem uso de abrasivos, nas amostras boretadas e não boretadas. A resistência à corrosão, das amostras boretadas e não boretadas, em HCl 0.1M foi avaliada por ensaios de polarização potenciodinâmica. Ensaios de oxidação do tipo quase-isotérmica foram realizados nas amostras, utilizando temperatura de 550°C ao ar. Para todas as condições de tratamento empregadas foram formadas camadas de boretos com elevadas durezas sobre os substratos. As propriedades das camadas como dureza, espessura, morfologia da interface camada/substrato e as fases presentes, foram influenciadas pelas composições dos aços. No caso do aço AISI H13, que possui maior quantidade de elementos de liga, as camadas formadas foram mais duras, menos espessas, com interface lisa, e para todas as condições de tratamento foram formadas os compostos de boro Fe2B, FeB e CrB. Já no aço AISI 1060 as interfaces camada/substrato foram do tipo dentada e para a temperatura de boretação de 900°C apenas a fase Fe2B foi formada, aparecendo o FeB a partir da temperatura de boretação de 1000°C. A resistência ao desgaste, corrosão e oxidação dos aços boretados aumentou significativamente, sendo que em relação ao desgaste, os melhores resultados foram obtidos com as amostras boretadas a 1000°C. Quanto à oxidação, os dois aços boretados a 900°C por 2h apresentaram os melhores desempenhos, e quanto à corrosão, os parâmetros do tratamento de boretação não influenciaram significativamente os desempenhos. / In this work the effect of pack boriding on wear, corrosion and oxidation resistance of AISI 1060 and AISI H13 steels were studied. Samples of the steels were pack borided at 900 and 1000°C for periods of 2 and 4h. Fixed-ball microwear tests were performed on borided and non-borided samples, without use of abrasives. The samples corrosion resistances, in HCl 0.1M, were evaluated by potentiodynamic polarization tests. Quasiisothermal oxidation tests were performed at 550°C on air. High hard layers were formed on steels for all treatment conditions employed. The layers properties, such as hardness, thickness, layer/substrate interface morphology and phases formed, were influenced by steels compositions. For AISI H13 steel, which has a larger amount of lloying elements, the formed layers were arder, thinner, with smooth interface and for all treatments conditions the compounds Fe2B, FeB and CrB were formed. For borided AISI 1060 steel, the layer/substrate interfaces showed a saw-tooth morphology and for boriding temperature of 900°C only the Fe2B phase were formed, appearing FeB for boriding temperature of 1000°C. The wear, corrosion and oxidation resistances of borided steels significantly increased and in relation to wear, the best results were btained with the samples borided at 1000°C. In oxidation case, both steels borided at 900°C for 2h showed the best performances, and with respect to corrosion, boriding treatments parameters did not significantly affect the performances.