Friction Stir Welding (FSW) is a new solid-state welding process that shows great promise for use in the aerospace and transportation industries. One of the primary benefits of this process is that mechanical properties of the base material are not as severely degraded as they are with conventional fusion welding. However, fatigue crack initiation and growth properties of the resulting weld nugget are not fully understood at this time. The primary goal of this project is to characterize the fatigue crack growth properties of friction stir welds in 6061-T6 aluminum as relates to the microstructural evolution of the weld. This was accomplished by producing friction stir welds and testing fatigue crack growth response in different crack orientations with respect to the weld. In addition, residual stress measurements were conducted for all cases, using both the crack compliance and contour methods. The results from the methods were compared in order to evaluate the accuracy of each method. Being an immature technology, the potential for discovery of new applications for the FSW process exist. With this in mind, novel applications of the FSW process, including the addition of particles during welding were explored. The first step was the investigation of property changes that occur when secondary cast phases are refined using the FSW process. The FSW process successfully refined all secondary phases in A380 and A356, producing an increase in hardness. Next, methods for the creation of particle metal matrix composites using FSW will be investigated. Nano-scale alumina particles were successfully added to the matrix and homogenously distributed. Using multiple weld passes through the composite was found to increase the uniformity of particle distribution. However, the alumina particle composite failed to provide any statistically significant hardness increase over the base material. The FSW process was also evaluated for weldability of traditionally difficult alloy systems. FSW was found to show very good weldability for dissimilar cast and wrought alloys, as well as for high-pressure die castings. Lastly, the feasibility of friction stir welding/processing in repairing crack defects in complex structural members in combination with cold-spray technology was determined. Friction Stir processing was used on a cold spray 6061-T6 block, resulting in significant increases in hardness over the base material, as well as a reduction in porosity. In addition, FSP was shown to eliminate crack-type defects in cold spray materials, a finding that has important applications in part repair. The deliverables of this work include an understanding of the fatigue crack growth response of FSW/FSP 6061-T6, as well as a feasibility study exploring novel uses for the FSW/FSP process. In addition, the deliverables include CNC code, fixtures, procedures, and analytical code for the creation and analysis of FSW/FSP joints. This will be important for the continuation of FSW/FSP work at WPI.

The effects of quenchant flow around a 4140 steel cylinder have been experimentally investigated. An apparatus was developed to repeatably immerse a two inch diameter by eight inch long probe into an agitated quench tank. The probes were normalized prior to quench to relieve any residual stresses. Distortion, residual stress and hardness were experimentally measured. The results verified that there was a variation of cooling rate in respect to quenchant flow around the cylinder. The data showed that there was a higher cooling rate nearest to the quenchant flow versus a much lower cooling rate away from the flow. Computational fluid dynamics are also presented to give insight into the behavior of the quenchant flow in the tank and around the cylinder.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-12-11T17:35:15Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Andre Assmann.pdf: 4986341 bytes, checksum: 7a618a74a9cd9fd887a2ad317c21334b (MD5) / Made available in DSpace on 2018-12-11T17:35:15Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Andre Assmann.pdf: 4986341 bytes, checksum: 7a618a74a9cd9fd887a2ad317c21334b (MD5) Previous issue date: 2018-10-30 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Medidas de tensão residual por microscopia de fluorescência é uma técnica bem estabelecida, que utiliza os picos de fluorescência R1 e/ou R2 dos íons Cr+3 em Al2O3. Esses picos são sensíveis à distorção da rede e sua frequência muda se o cristal estiver sob tensão. Amostras sinterizadas de vidro borossilicato e de soda-cal com a adição de 10 vol.% Al2O3 foram produzidas por mistura dos pós de vidro e alumina, prensagem uniaxial e sinterização em alta temperatura. A morfologia e microestrutura da superfície foram caracterizadas por microscopias ótica e eletrônica de varredura. A porosidade obtida foi inferior a 2%. Foram realizados indentações com carga de 10 N Vickers e as tensões ao redor das indentações foram medidas por microscopia de fluorescência. As medidas de tensões residuais devido à diferença de expansão térmica entre a matriz de vidro e as partículas de Al2O3 foram de 163 MPa e -35 MPa para amostras sinterizadas de borossilicato e soda-cal, respectivamente, em concordância com o modelo de Hseuh & Becher. A função de convolução do feixe de luz incidente (PRF) foi ajustada aos dados de fluorescência levando em conta a interação do feixe de laser dentro da amostra e os efeitos de absorção, refração e espalhamento do feixe de luz incidente por partículas de alumina e por poros e também por gradientes de tensões ao redor de indentações. O deslocamento experimental de fluorescência em função da distância da borda da indentação foi comparado com o modelo de Yoffe e com a função PRF. Verificou-se que a intensidade experimental do campo de indentação é 10 vezes menor que o previsto pelo modelo de Yoffe mesmo levando em consideração a densificação do vidro embaixo do penetrador. As tensões residuais de indentações também foram medidas para o vidro soda-cal usando o modelo modificado de Zeng e Rowcliffe. Os perfis de tensão foram medidos em torno de indentações Vickers realizadas com cargas de 50 N e 100 N em temperaturas entre -196 °C e 400 °C. A intensidade do campo aumentou com a temperatura e isso pode ser explicado pela variação da razão / com a temperatura. Este trabalho contribui para a compreensão dos mecanismos responsáveis pelas tensões residuais causadas por indentação em vidros. / Residual stress measurements by fluorescence microscopy is a well-established technique which uses the R1 and/or R2 fluorescence peaks of Cr+3 ions in Al2O3. These peaks are sensitive to the distortion of the lattice and their position changes if the crystal is stressed. Borosilicate (BS) and soda-lime (SL) sintered samples with 10 vol. % Al2O3 were produced mixing the glass and alumina powders, uniaxial compressed and sintered at high temperature. Surface morphology and microstructure were characterized by optical and scanning electron microscopies. The porosity obtained was less than 2%. 10 N Vickers indentations were performed and the stresses around the indentations were measured by fluorescence microscopy. Measurements of residual stresses due to thermal expansion mismatch between the glass matrix and the Al2O3 were 163 MPa and -35 MPa for BS and SL composites samples, respectively, in agreement with Hseuh & Becher’s model. The probe response function was fitted to the fluorescence data taking into account the iteraction of the laser beam within the sample and effects of light absorption, refraction and scattering by alumina particles and pores and stresses gradients. The experimental fluorescence shift as a function of the distance from the indentations was compared with Yoffe’s model and the PRF function. It was found that the experimental blister field strength is a factor of 10 smaller than that predicted by Yoffe´s model, taking into account the densification of the glass underneath the indenter. Indentation residual stresses were also measured for SL glass using the Zeng and Rowcliffe’s model. Stress profiles were measured around 50 N and 100 N Vickers indentations performed between -196 °C to 400 °C. The blister field strength increased with temperature and it could be explained by the variation of the / ratio with temperature. This work contributes for the understanding of the mechanisms responsible for the indentation residual stresses in glasses.

Residual stresses are generally considered to be the driving forces for the failure of APS TBCs. In this thesis, the residual stress distribution as a function of depth in APS TBC has been measured by synchrotron XRD and explained by image based modelling based on the microstructure detailed studied by SEM and CT. The residual stress/ strain distribution as a function of depth was measured by synchrotron XRD in transmission and reflection geometry. The residual stress/ strain values were analysed using full pattern Rietveld refinement, the sin square psi method and XRD2 method. For the reflection geometry, a new method was developed to deconvolute the residual stress value in each depth from the measured averaged values. Two types of residual stress/strain distribution were observed. The first kind of residual stress was found to be compressive and followed a non-linear trend, which increased from the surface to the interface, decreased slightly and increased again to the interface. This trend showed a jump feature near the interface. The second kind of residual stress distribution possessed two jump features: one near the interface similar to the first kind and another jump feature near the sample surface. The residual stress in both beta and gama phase in the bond coat were also investigated which showed a tensile stress state. The stress trend predicted by our analytical model followed a linear relationship. Comparing this with the first kind of residual stress distribution, two main differences were shown. Firstly the jump feature near the interface and secondly the much larger overall stress gradient. The 3D and 2D microstructure of the sample with the first kind of residual stress distribution was observed by X-ray CT and SEM. The effect of pores, inter-splat cracks and the rumpling interface on the residual stress distribution was investigated by image based modelling. It was proved that the pores and the inter-splat cracks had no large influence on the stress distribution and the jump feature near the interface was a result of the rumpling interface. The much larger stress gradient observed in the measured residual stress distribution was an indication of the stress relaxation in the coating which was proved by a specially designed mechanical test. To explain the jump feature near the sample surface in the second kind of stress distribution. 3D microstructures of the measured samples were observed using X-ray CT. The effect of vertical and the side cracks on the stress distribution were investigated by image based modelling. It was found that the vertical crack had no large influence on the residual stress distribution and the jump feature in the stress trend near the surface could be attributed to the side crack. The effect of other kinds of cracks that were not directly observed in our samples, such as middle or through side cracks, were also investigated. These results were used to develop a semi-destructive method to determine the existence and distribution of cracks in APS TBC.

Stationary shoulder friction stir welding (SSFSW) is a recently developed variant of conventional friction stir welding (FSW). Recent studies have shown that SSFSW can join high strength aluminum alloys with improved mechanical strength and reduced distortion as a result of a narrower and more uniform thermal profile. However, a lack of understanding on the residual stress development in the SSFSW process makes it difficult to assess the structural integrity and delays a widespread application of this technique to industry. This dissertation reports the first systematic investigation into the development of residual stress induced by the SSFSW process and comparison between SSFSW and FSW techniques. Welding residual stresses were experimentally assessed with both the contour method and neutron diffraction. The weld microstructure and hardness distributions were characterized and used to understand the formation of residual stresses during the welding process. The results have shown that for both FSW and SSFSW processes, the residual stresses distribute in the form of ‘M’ shaped profile while the magnitude and size of tensile residual stress zone were effectively reduced (by 25%) in the SSFSW process, even when input welding power was identical. Other improvements seen in the SSFSW process include a reduction in the heat affected zone width, an increase in the minimum hardness and a more uniform through-thickness microstructure and hardness. The dominating welding process parameter affecting the welding residual stress was travel speed as compared to rotation speed and tool downforce. With a 90 degree shaped shoulder, SSFSW has been shown to produce defect-free T-sections by dual fillet welds. For these components, an asymmetrical distribution of microstructure, hardness and residual stresses were found as a consequence of the thermal effects induced by second weld on the first weld. The material softening caused by the first weld provides the potential of utilizing a lower heat input on the subsequent pass so as to optimize the welding parameters.

Residual stresses are the stresses which are present within a component without any external load. They can be introduced through any number of manufacturing processes and in-service conditions, meaning that they are almost ubiquitous in engineering components. The characterisation of residual stress is an important field of research particularly in an engineering context since the effects of residual stress sum with the loads. As a result, the performance of a component can be greatly enhanced, or significantly reduced, by the presence of residual stress depending on the sign of the stress and the applied load. In this EngD thesis the focus has been on the development of residual stress through the manufacturing processes of aero-engine forgings, specifically the turbine disc. The forgings studied were sub-scale geometries of the disc, forged from the nickel-base superalloy RR1000. The overall aim of this work is to improve the understanding of the residual stress generation and relaxation through implementation of advanced experimental characterisation techniques, with a view to improving current stress predicting process modelling capabilities. With this in mind the work has focussed on the use of neutron diffraction and the contour method to characterise residual stress experimentally, while residual stress predictions have been made using finite element modelling. The findings of this research indicated that very large residual stresses were generated as a result of the quenching process, and that these stresses were then relaxed and redistributed by ageing heat treatments and material removal by machining. The results obtained through the two experimental techniques exhibited very strong agreement, indicated a robust experimental process. Comparisons to the finite element predictions highlighted some issues with the current model; in particular it was found that the simulation of quenching could be improved by better definition of the heat transfer at the surface. Furthermore, the level of stress relaxation during ageing was consistently over predicted in the model. This result is thought to be the result of an over-prediction of the level primary creep in the alloy. Subsequent studies will investigate this behaviour further using the newly developed in-situ heat treatment capabilities which have developed as part of this research.

The worldwide preferred method for rail joining is welding; flash butt welding (FBW) and thermite welding (TW) are the two main welding methods used for joining continuous welded rail (CWR) tracks. However, the welds still represent a discontinuity in the track structure due to variations in microstructure, mechanical properties and residual stress levels with respect to the parent rail. These variations can play significant roles in increasing the risk of weld failure under service conditions. In order to better understand how FBW parameters affect these variations, the two main parameters; number of preheating cycles and upsetting forces were varied in three 56E1 rail welds, welded by a stationary FBW machine. Besides, these variations were systematically compared with those that occur in a standard thermite 60E2 rail weld. The thermite weld showed a heat affected zone (HAZ) extent much greater than those measured in the flash butt welds. The flash butt rail weld with a greater upsetting force (Standard Crushed) showed a HAZ extent larger than those in the other two welds (Standard Uncrushed and Narrow-HAZ Crushed), while the weld with fewer preheating cycles (Narrow-HAZ Crushed) showed a smaller extent of the HAZ.All welds showed pearlite colonies with proeutectoid ferrite at the prior austenite grain boundaries in the weld centre, and in the thermite weld zone. The rest zones across the welds exhibited almost fully pearlitic microstructures, but the pearlite at nearly the visible HAZ extents was partially spheroidised. The partially spheroidization zone had the minimum hardness across each of the thermite and flash butt welds. The Narrow-HAZ Crushed weld showed hardness in the weld centre, on average, higher than that of the parent metal. Moreover, the averaged hardness levels in this weld were significantly higher than those in the other two welds. However, these levels in the Standard Crushed weld were slightly lower than those in the Standard Uncrushed weld. Although the visible HAZ extent coincided with the point of minimum hardness, the residual stresses arising from the welds seem to extend much further. Contour Method and laboratory X-ray diffraction techniques were used together to measure the residual stress components across the thermite and flash butt rail welds. The longitudinal residual stress distribution showed tension in the web region along with compression in the head and foot regions of the rail welds. The vertical stress distribution across the flash butt welds was generally similar, and the maximum tensile stress values were comparable to those in the longitudinal direction. While the maximum values of the longitudinal tensile stress increased with decreasing the HAZ widths, these values in the vertical direction were significantly unaffected. However, the longitudinal and vertical tensile residual stresses typically promote the vertical straight-break and horizontal split web failure modes respectively.

No presente trabalho foram estudados alguns efeitos causados pelo jateamento por granalhas no aço Cr-Si-V, processo que tem por objetivo aumentar a resistência à fadiga. Para este estudo a variação de parâmetros no processo são ferramentas para melhor compreender os mecanismos que influenciam esta propriedade. Os parâmetros utilizados neste trabalho foram a variação da granalha e o pré tensionamento das amostras aplicados em lâminas utilizadas em feixe de molas automobilísticas de aço de liga cromo silício vanádio (SAE 9254+V). Inicialmente foi realizada a avaliação do perfil de tensão residual, efetuada por difração de raios-x pelo método do sen2 ao longo da espessura na região onde a tensão é compressiva. Nos resultados nota-se um efeito anômalo em relação ao perfil característico da distribuição de tensão residual com a perda de compressão nas camadas iniciais em relação à superfície jateada. Com o uso da microscopia eletrônica de varredura foi observado a região afetada pelo jateamento por granalhas notando que as regiões plasticamente deformadas se encontram nas mesmas regiões onde ocorre a diminuição da tensão residual compressiva. O perfil obtido pela difração de raios-x fornece as informações necessárias com o propósito de conjugar os efeitos que a microtensão (microdeformação) influenciam na macrotensão (tensão residual). Esta relação foi comprovada pela sobreposição dos resultados encontrados na distribuição da microdeformação da rede cristalina com a tensão residual ao longo da espessura na região plasticamente deformada. Os resultados dos perfis das difrações de raios-x mostraram a existência de anisotropia de tensões entre os planos, geradas por defeitos de empilhamento e pela densidade de discordâncias. Assim sendo, para obter os valores das microtensões devem ser considerados os fatores das constantes elásticas (conforme o módulo das direções) e dos planos cristalográficos. O método aplicado foi o Williamson-Hall modificado. Além deste método outros também foram utilizados, tais como: método de Warren-Averbach e o método Single Line, este aplicando a série de Fourier, porém, ao observar os resultados, nota-se a diferença entre os valores obtidos nas deformações, tanto aos métodos quanto aos planos cristalográficos, porém a ênfase deste trabalho foi dada às características dos perfis da distribuição e não aos valores absolutos. Somando a isto, foi proporcionado o estudo da distribuição do tamanho médio de cristalito ao longo da espessura no perfil das difrações de raios-x e os resultados mostraram que esta distribuição varia de forma inversa a microdeformação. A relação entre o tamanho médio de cristalito e a variação das distâncias interplanares corresponde diretamente a alterações das densidades de discordâncias ocorridas no material que por sua vez estão ligadas às microdeformações da rede cristalina. Como complemento ao trabalho foram analisados o fator de concentração de tensão e ensaios de fadiga do material. O fator de concentração de tensão não variou conforme a utilização das granalhas S330 e S390, ambas sendo aplicadas no mesmo regime de jateamento. Os ensaios de fadiga indicaram que o pré tensionamento aumenta a vida útil nas tensões cíclicas do material estudado. / In the present work, some effects caused by jateamento por granalhas on Cr-Si-V steel have been studied, a process that aims to increase fatigue resistance. For this study the variation of parameters in the process are tools to better understand the mechanisms that influence this property. The parameters used in this work were the variation of the grit and the pre-tensioning of the samples applied in leafs used in automotive springs of chrome silicon vanadium alloy steel (SAE 9254 + V). Initially the evaluation of the residual stress profile was performed by x-ray diffraction using the sen2 method along the thickness in the region where the stress is compressive. The results show an anomalous effect in relation to the characteristic profile of the residual stress distribution with the decrease of compression in the initial layers in relation to the blasted surface. With the use of scanning electron microscopy, the region affected by grit blasting was observed, noting that the plastically deformed regions are located in the same regions where the compressive residual stress decrease. The profile obtained by X-ray diffraction provides necessary information with the aim of combining the effects of microstress (microstrain) on macrostress (residual stress). This relationship was confirmed by the overlap of the results found in the distribution of the microstrain of the crystalline lattice with the residual stress along the thickness in the plastically deformed region. The results of the x-ray diffraction tests show an existence of tensile anisotropy between the planes generated by stacking faults and the dislocations density. Therefore, to obtain the values of the microstress must be considered the factors of the elastic constants and the crystallographic planes. The method applied was the modified Williamson-Hall. Beyound this method, others were also used, such as: Warren-Averbach method and the Single Line method, this applying the Fourier series, however, when observing the results, we can notice the difference between the values obtained in the deformations, however, the emphasis of this work was on the characteristics of the distribution profiles and not on the absolute values. In addition, the study of the distribution of the mean crystallite size along the thickness of the X-ray diffraction profile was provided and the results showed that this distribution varies inversely with microstrain. The relationship between the mean crystallite size and the variation of the interplanar distances corresponds directly to changes in the densities of dislocations occurring in the material, which in turn are linked to the microstrain of the crystalline lattice. As a complement to the work, the stress concentration factor and fatigue tests of the material were analyzed. The stress concentration factor did not change according to the use of the S330 and S390 grit, both being applied in the same blasting regime. Fatigue tests indicated that pretensioning increases the useful life of the cyclic stresses of the material studied.

A liga de alumínio 6082 apresenta de média para alta resistência mecânica e é de grande importância no mercado de perfis extrudados. O processo de jateamento com granalha de aço em componentes automotivos e aeronáuticos, visando induzir uma condição otimizada de tensão residual de compressão na superfície, tem se mostrado eficaz na melhoria das propriedades mecânicas em fadiga desses componentes. Neste sentido, este trabalho tem como objetivo estudar os efeitos do jateamento com granalhas de aço na tensão residual e no comportamento mecânico em fadiga da liga de alumínio 6082 solubilizada e envelhecida artificialmente. Inicialmente foram feitos tratamentos térmicos de solubilização e envelhecimento artificial visando a determinação da melhor condição em termos de resistência mecânica da liga de alumínio 6082. A seguir foram realizados experimentos com diversos tipos de granalhas esféricas de aço e em condições variadas de jateamento (velocidade de rotação e tempo), definindo-se a melhor condição de tensão residual medida por difração de raios x. Ensaios de fadiga em corpos de prova jateados com granalha de aço na melhor condição de tensão residual foram executados em máquina flexo-rotativa e comparados com os resultados do material sem jateamento. A melhor condição de tensão residual ocorreu em decorrência do jateamento com o uso da granalha de aço S170PEE, rotação da turbina à 2500 rpm e tempo de exposição de 1 minuto. A curva de tensão residual em profundidade para a condição escolhida apresentou resultados coerentes somente até 76 μm devido à presença de grãos grandes em profundidades superiores a esta. As curvas S-N mostraram que houve um ganho na vida em fadiga em tensões elevadas e baixo número de ciclos para romper devido jateamento com granalha de aço. Ao contrário, ocorreu um efeito deletério na vida em fadiga em tensões baixas e número de ciclos elevados para romper, devido à influência do aumento da rugosidade em ensaios de fadiga mais longos. / Aluminum alloy 6082 exhibits medium to high strength and is widely used as extruded products. Shot peening of automobile and aircraft components, carried out to induce optimum residual compressive stress on the surface, improves fatigue properties of these components. In this context, the aim of this investigation was to study the effects of shot peening on the residual stress and fatigue behavior of solution treated and artificially aged 6082 aluminum alloy. Initially, solution treatment and artificial ageing of this alloy were carried out to determine the best conditions in terms of alloy strength. Subsequently, experiments were carried out with different types of spherical steel shots, under a variety of peening conditions (rotation speed and duration), to define the best set of conditions to increase residual stress that was measured using x-ray diffraction. Fatigue tests were carried out using a rotating-bending machine on shot peened specimens that had the highest residual stress. These results were compared with those of specimens that were not shot peened. The highest residual stress was observed when peening was done with S170PEE steel shots, at 2500 rpm for 1 minute. The variation in residual stress as a function of depth, for the above-mentioned peening conditions, was coherent only up to a depth of 76 μm and attributable to the presence of large grains at depths higher than this. The S-N curves revealed an increase in fatigue life at high stresses and at low cycles to failure and attributed to shot peening. Contrary to this, a deleterious effect in terms of reduction in fatigue life was observed at low stresses and at high cycles to failure, due to increase in surface roughness of the specimens during the extended fatigue tests.

O estudo de usinabilidade de um material é muito importante para a determinação das características de fabricação por usinagem. Este estudo se aplica ao aço inoxidável martensítico AISI 420 C endurecido, usado na fabricação de peças de alta precisão, instrumentos cirúrgicos, eixos, turbinas e cutelaria. Deste modo, realizaram-se investigações utilizando corpos de prova endurecidos (têmpera e revenimento) com durezas de (48  1) e (53  2) HRC no torneamento a seco utilizando ferramentas de metal-duro classe ISO S com grãos extrafinos e revestimento PVD. Para estes corpos de prova variaram-se a velocidade de corte e o avanço e avaliaram-se as forças de usinagem e as tensões residuais geradas na peça. Para o material com 53 HRC, também foram analisadas a vida da ferramenta e a rugosidade. Na análise dos resultados obtidos para o material com 48 HRC, as tensões residuais tornaram-se menos compressivas (circunferencial) e mais trativas (axial) com o aumento do avanço. Além disso, os menores valores de tensão residual foram gerados utilizando menor avanço com maior velocidade de corte. Nos ensaios para o material a 53 HRC, o tempo de vida da ferramenta ficou entre 100 e 350 min para as condições ensaiadas. Os desgastes de flanco e entalhe foram evidenciados em todas as situações. O flanco da ferramenta também apresentou adesão de material da peça em todas as condições. Ao analisar os insertos em seu fim de vida, constatou-se que os mecanismos de desgastes predominantes foram a abrasão e o atrittion. Nas condições mais severas, a superfície da ferramenta exibiu trincas mecânicas e a camada subsuperficial da peça apresentou modificações microestruturais. Os perfis e os parâmetros de rugosidade registrados foram afetados pelo desgaste ao longo da vida da ferramenta. Com relação às tensões residuais circunferenciais geradas com a ferramenta nova, estas foram, em sua maioria, tensões de compressão. Com a progressão do desgaste de flanco, houve um aumento dos valores das tensões (de compressivas para menos compressivas ou até mesmo trativas). Já para as tensões axiais, os valores mostraram a tendência de se manterem compressivos. Observou-se para os perfis de tensões analisados que as tensões residuais foram compressivas e dependeram da profundidade da camada subsuperficial. Portanto, dentro das condições estudadas, conclui-se que peças de AISI 420 C endurecido podem ser fabricadas por torneamento de acabamento com ferramentas de metal-duro, permitindo obter vida longa para a ferramenta de corte, baixos valores de rugosidade, bem como valores de tensão residual compressiva, que são dados de usinabilidade importantes para esse material. / The study of the material’s machinability is very important for the determination of important machining properties. This logic applies to hardened martensitic stainless steel AISI 420 C used in the manufacture of high precision parts, surgical instruments, shafts, turbines and cutlery. In this way, investigations were carried out using hardened workpieces (quenching and tempering) with hardness of (48  1) and (53  2 HRC) in dry turning using ISO-S grade carbide tools with extra-fine grains and PVD coating. For these workpieces, the cutting speed and the feed rate were varied and the machining forces and the residual stresses generated in the part were evaluated. For the material with 53 HRC, the tool-life and the surface roughness were also analyzed. In the analysis of the results obtained for the material with 48 HRC, residual stresses become less compressive (circumferential direction) and more tensile (axial direction) with increasing feed-rate. Moreover, smaller values of residual stress were generated using lower feed-rate at higher cutting speed. In the tests for the material at 53 HRC, the tool-life was between 100 and 350 min for the conditions tested. Flank and notch wear were evidenced in all situations. The flank face of the tool also showed adhesion of the workpiece material under all cutting conditions. When analyzing the inserts at their end of life, it was verified that the main mechanisms of tool wear were abrasion and attrition. In addition, under the most severe cutting conditions, the flank face of the tool exhibited mechanical cracks and the subsurface layer of the workpieces presented microstructural modifications. The registered profiles and roughness parameters were affected by wear during the tool-life. With respect to the circumferential residual stresses generated with the fresh tool, these were mostly compressive stresses. With the progression of tool flank wear, there was an increase in the values of the residual stress (from compressive to less compressive or even tractive). For the axial residual stresses, the values showed a tendency to remain compressive. It was observed for the residual stress profiles analyzed that the residual stresses were compressive and depended on the depth of subsurface layer. Therefore, within the cutting conditions considered, it can be concluded that hardened martensitic stainless steel AISI 420 C parts can be manufactured by finishing turning with carbide tools, allowing long tool-life, low surface roughness values, as well as compressive residual stress values, which are important machinability information for this material.