PrimeTurning™ is a new turning technology, which consists of tools and programming method. By using this method, it has been demonstrated that higher material removal rates and flexibility in turning can be obtained.  The New Product Industrialisation department at AB Sandvik Coromant works with development of production processes and improvements in current processes.Machining tests are carried out in order to improve production performance, and find optimised solutions.  In this master thesis work, the effect of insert grades and entering angles on wear and tool life while machining hardened tool steel has been studied. Machining experiments have been carried out to analyse wear and tool life by using the PrimeTurning™ method.Two approaches of experimental design have been investigated, and a suitable design is selected for conducting the experiments.  The performance of these insert grades and tool holders (κ=21° and κ=25°) has been compared to each other and the existing production scenario, and a recommendation is made regarding insert grade,tool holder and cutting parameter selection for machining hardened tool steel using PrimeTurning™. The wear analysis has been performed by using a stereo microscope coupled with an image processing software to measure the flank wear length. Flank wear, flaking and chipping have been observed as the major wear types.  As a result, it has been identified that the insert grade GXXC, coupled with the tailor-made tool holder performs significantly better than the currently used insert and tool holder in production. A substantial increase in tool life increase is observed, even when machining at a higher Material Removal Rate of 29%. This would result in a significant increase productivity, if the results can be reproduced in production. / PrimeTurning ™ är en ny svarvningsteknik som består av verktyg och programmeringsmetod. Genom att använda denna metod har det visats att högre materialavlägsningshastigheter och flexibilitet vid svarvning kan uppnås.  Avdelningen för nyproduktionsindustrialisering på AB Sandvik Coromant arbetar med utveckling av produktionsprocesser och förbättringar av nuvarande processer. Maskintester genomförs för att förbättra produktionsprestanda och hitta optimerade lösningar  I det här examensarbetet som utförts vid AB Sandvik Coromant har effekten av skärsorter och ställvinklar på slitage och livslängd vid bearbetning av härdat verktygsstål studerats. Maskinbearbetningsexperiment har utförts för att analysera slitage och verktygslivslängd med hjälp av PrimeTurning ™ -metoden. Två metoder för experimentell design har undersökts och en lämplig design väljs för att utföra experimenten.  Prestandan hos dessa skärsorter och verktygshållare (κ = 21 ° och κ = 25 °) har jämförts med varandra och det nuvarande produktionsscenariot, och en rekommendation görs beträffande skärsort, verktygshållare och val av skärparametrar för maskinbearbetning av verktygsstål med PrimeTurning ™. Förslitningsanalysen har utförts med användning av ett stereomikroskop kopplat till en bildbehandlingsprogramvara för att mäta längden av fasförslitningen. Fasförslitning, urflisning och flagning har observerats som de viktigaste typerna av förslitning.  Studiens resultat visar att skäret GXXC, i kombination med den skräddarsydda verktygshållaren presterar avsevärt bättre än det för närvarande använda skäret och verktygshållaren i produktionen. En kraftig ökning av livslängden på verktyg observeras även vid bearbetning med en högre Spånavverkningshastighet på 29%. Om dessa resultat kan reproduceras i produktionen kan en betydande produktivitetsökning erhållas.

The effect of three heat treatments on plane-strain fracture toughness (K _Ic), fatigue crack growth rate (da/dN), and tensile behavior of a commercial powder metal alloy, CPM 10V, was investigated. Fracture toughness was increased by increasing the tempering temperatures and decreased by increasing the austenitizing temperature. These changes were related to changes in yield strength and the resulting crack tip plastic zone sizes. Fracture toughness resulting from any of the three heat treatments was inversely related to the hardness. Fatigue crack growth followed the Paris Law for some portion of the curve and crack growth exponents, n, were virtually unchanged by the heat treatment. The linear portion of the growth curve was shifted to higher stress intensity ranges for heat treatments yielding higher fracture toughness. Fatigue crack growth behavior in the high growth region was determined mainly by the fracture toughness of the specific heat treatment. / M.S.

Os aços ultra-resistentes e os sinterizados estão bem estabelecidos tecnologicamente, sendo utilizados nas mais variadas aplicações. Entretanto para certas situações, como é o caso de componentes sujeitos aos desgaste severo, existe a necessidade de se melhorar suas propriedades superficiais. Dentre as técnicas de endurecimento superficial, a nitretação iônica se apresenta como uma boa alternativa para o tratamento desses aços, uma vez que as peças ficam menos suscetíveis a empenamentos e distorções, como ocorre em outros tratamentos superficiais convencionais e permite o controle adequado da camada produzida. O presente trabalho tem por objetivo estudar o efeito do silício em aços ultra-resistentes com relação ao tratamento térmico bem como a influência desse elemento na nitretação e conseqüentemente no desgaste abrasivo e verificar a influência do V sobre essas mesmas características no caso de aços sinterizados. Foram utilizadas oito ligas, com diferentes teores de silício e vanádio, que foram nitretados ionicamente em diferentes condições de temperatura e/ou tempo. As camadas nitretadas obtidas foram avaliadas por meio de ensaios de microdureza na superfície e na seção transversal, microscopia ótica e eletrônica de varredura, com microssonda (EDX), análise por difração de raios X e ensaios de abrasão do tipo \"pino-sobre-disco\". Observou-se que, com o aumento do teor de silício, nas ligas ultra-resistentes aumentou a dureza após o revenido e que a presença desse elemento aumenta consideravelmente a dureza da camada nitretada. O aumento do teor de silício produziu camadas de compostos menos espessas e de alta dureza, que apresentaram as melhores resistência ao desgaste abrasivo. As análises superficiais por meio de raio X demonstraram que essas camadas são formadas por uma mistura de nitretos &#947\'-Fe4N, &#949Fe2-3N, CrN, MoN e Si3N4, que variam suas proporções com as condições de nitretação. Nas ligas sinterizadas as durezas das camadas aumentaram consideravelmente depois da nitretação iônica, devido a formação de VN. No ensaio de desgaste abrasivo verificou-se que tal aumento de dureza resultou em uma menor perda de massa, quando a camada de compostos é constituída significativamente de VN e &#947\'- Fe4N. O incremento do tempo de tratamento não influenciou na forma e tamanho dos carbonetos presentes nesses aços. / The ultra-strength and sintered steels are technologically very established, being used in the most varied applications. In the cases where the main selection requirements are the mechanical resistance and the cost of the material, those steels are an interesting option. However for certain applications, as it is the case of components subject to the severe wear, the need exists of improving its surface properties. Among the techniques of superficial hardening, the ion nitriding present it self as a good alternative for the treatment of those steels, once the specimen are less susceptible to the warpage and distortions, as it happens in another conventional superficial treatments. The objective of the present work is to study the effect of the Si in ultra-strength steels relating it to the heat treatment as well as the abrasive wear resistance of the same and of sintered tool steels with variable content of V, after ion nitriding. Eight alloys were used with different content of Si and V. The alloys were ion nitrided in different conditions of temperature and/or time. The nitrided layers obtained were appraised by means of microhardness test in the surface and in the cross section of the layers, optical and scanning electron microscopy (SEM), with energy dispersive spectrometry (EDS), analysis for X-ray diffraction and \"Pin-on-Disc\" type abrasion test. It was observed that with the increase of the content of Si in the ultra-resistant alloys, increased the hardness after the tempering and the presence of that element it increases the hardness of the nitrided layer considerably. The increase of the content of Si produced smaller compound layers and of high hardness, that presented the best resistance to the abrasive wear. The superficial analysis by means of X-ray has shown that the compound layers are formed by a mixture of &#947\'-Fe4N, e-Fe2-3N, CrN, MoN and Si3N4, nitrides that vary its proportions with the nitriding conditions. In the sintered alloys the hardness of the layers increased considerably after the ion nitriding, due to formation of VN. In the test of abrasive wear it was verified that such increase of hardness results in a smaller mass loss, when the compound layer is constituted of VN and &#947\'-Fe4N phase. The increase of time of treatment did not influence in the shape and size of the present carbides in the steels.

Durante o desgaste por deslizamento há a ocorrência de calor gerado por atrito, que favorece a oxidação nas superfícies de contato dos metais. O resultado deste fenômeno pode provocar uma diminuição da taxa de desgaste, a qual usualmente é associada com transições no tipo de contato: metal-metal, metal-óxido ou óxido-óxido. Este trabalho tem como objetivo desenvolver um modelo teórico do desgaste oxidativo. O modelo tenta correlacionar parâmetros termodinâmicos e tribológicos dos materiais, como energia de Gibbs, carga, área real de contato, velocidade e temperatura do contato. Para testar o modelo, realizaram-se ensaios do tipo pino-sobre-disco convencional, para análise da influência dos parâmetros tribológicos, de forma a obter diversas relações entre temperatura de contato, carga, velocidade e as propriedades físico-químicas dos materiais. Os ensaios foram realizados com variação contínua de carga, em intervalos de 20 a 120 N, 20 a 80 N e de 20 a 40 N. Os materiais escolhidos para serem ensaiados foram pino de aço ferramenta M2 temperado e revenido, enquanto que o disco foi de aço 1045 austemperado com microestrutura do tipo bainítica. A caracterização superficial antes e depois dos ensaios foi feita usando-se diferentes técnicas auxiliares, tais como microscopia óptica e eletrônica de varredura. Analisando as curvas obtidas a partir do modelo, assim como as obtidas pelas análise das experiências feitas para sua avaliação, pôde-se concluir que força motriz que causa a taxa de desgaste é a energia de contato, a qual depende das condições físico-químicas, do meio e das solicitações impostas às condições de contato, sendo também as propriedades do material essenciais para a influência na taxa de desgaste, propriedades que estão intrínsecas no modelo, assumindo a energia de Gibbs do material. / During sliding wear, heat generated friction occurs, which favors oxidation occurrence on the contacting surfaces of metallic materials. The oxidation phenomenon can result in wear rate attenuation due to transitions in the contact feature from metal-metal to either metal-oxide or oxide-oxide. This work aimed to develop a theoretical modeling on oxidational wear. In the obtained model, both thermodynamic and tribological parameters were used, such as Gibbs energy, load, actual area of contact, velocity and contact temperature. In order to obtain experimental data for the model assessment, usual pin-on-disk tests were conducted under some load and velocity conditions. Relations among the variables, such as contact temperature, load, velocity and physical-chemical properties of the materials, were attained. The tests were performed under continuous rising on load. Intervals from 20 to 120 N, 20 to 80 N and 20 to 40 N were tested. The pin material was made of quenched and tempered M2 tool steel and the disks were of austempered AISI 1045 steel with bainitic microstructure. Surface characterization was carried out before and after the tests, through optical and scanning electronic microscopes. Analyzing the results obtained from the model and from the experimental tests, it was possible to conclude that the wear phenomenon is related to the contact energy, which depends on the physical-chemical conditions of the surfaces, the environment and the mechanical loading the surfaces undergo. The material properties, which do also influence the wear rate, were taken into consideration in the model as the Gibbs energy of the materials.

Durante o desgaste por deslizamento há a ocorrência de calor gerado por atrito, que favorece a oxidação nas superfícies de contato dos metais. O resultado deste fenômeno pode provocar uma diminuição da taxa de desgaste, a qual usualmente é associada com transições no tipo de contato: metal-metal, metal-óxido ou óxido-óxido. Este trabalho tem como objetivo desenvolver um modelo teórico do desgaste oxidativo. O modelo tenta correlacionar parâmetros termodinâmicos e tribológicos dos materiais, como energia de Gibbs, carga, área real de contato, velocidade e temperatura do contato. Para testar o modelo, realizaram-se ensaios do tipo pino-sobre-disco convencional, para análise da influência dos parâmetros tribológicos, de forma a obter diversas relações entre temperatura de contato, carga, velocidade e as propriedades físico-químicas dos materiais. Os ensaios foram realizados com variação contínua de carga, em intervalos de 20 a 120 N, 20 a 80 N e de 20 a 40 N. Os materiais escolhidos para serem ensaiados foram pino de aço ferramenta M2 temperado e revenido, enquanto que o disco foi de aço 1045 austemperado com microestrutura do tipo bainítica. A caracterização superficial antes e depois dos ensaios foi feita usando-se diferentes técnicas auxiliares, tais como microscopia óptica e eletrônica de varredura. Analisando as curvas obtidas a partir do modelo, assim como as obtidas pelas análise das experiências feitas para sua avaliação, pôde-se concluir que força motriz que causa a taxa de desgaste é a energia de contato, a qual depende das condições físico-químicas, do meio e das solicitações impostas às condições de contato, sendo também as propriedades do material essenciais para a influência na taxa de desgaste, propriedades que estão intrínsecas no modelo, assumindo a energia de Gibbs do material. / During sliding wear, heat generated friction occurs, which favors oxidation occurrence on the contacting surfaces of metallic materials. The oxidation phenomenon can result in wear rate attenuation due to transitions in the contact feature from metal-metal to either metal-oxide or oxide-oxide. This work aimed to develop a theoretical modeling on oxidational wear. In the obtained model, both thermodynamic and tribological parameters were used, such as Gibbs energy, load, actual area of contact, velocity and contact temperature. In order to obtain experimental data for the model assessment, usual pin-on-disk tests were conducted under some load and velocity conditions. Relations among the variables, such as contact temperature, load, velocity and physical-chemical properties of the materials, were attained. The tests were performed under continuous rising on load. Intervals from 20 to 120 N, 20 to 80 N and 20 to 40 N were tested. The pin material was made of quenched and tempered M2 tool steel and the disks were of austempered AISI 1045 steel with bainitic microstructure. Surface characterization was carried out before and after the tests, through optical and scanning electronic microscopes. Analyzing the results obtained from the model and from the experimental tests, it was possible to conclude that the wear phenomenon is related to the contact energy, which depends on the physical-chemical conditions of the surfaces, the environment and the mechanical loading the surfaces undergo. The material properties, which do also influence the wear rate, were taken into consideration in the model as the Gibbs energy of the materials.

This thesis looks at the capabilities of cutting thin webs on Wire EDM machines that are difficult or impossible to machine using conventional methods. Covered is an investigation of how different material and web thickness affect the capability of machining thin-walled parts. Five different metals are used for the test; Aluminum 6061 T6, Yellow Brass SS360, 420 Stainless Steel, D2 unheat-treated tool steel 25-30 RC, and D2 heat-treated tool steel 60-65 RC. The small parts were cut to a 6mm (0.2362 inch) height with six different wall thicknesses: 0.30mm (0.0118 inch), 0.25mm (0.0098 inch), 0.20mm (0.0078 inch), 0.15mm (0.0059 inch), 0.10mm (0.0039 inch), and 0.05mm (0.0020 inch). A Sodick AQ325L Wire EDM machine was utilized for testing. The methods employed during the study include the following: • Machine settings and offsets were limited to the default setting selected from the Sodick AQ325L database. • Two different pre-test cuts were taken on the material to check for web bending during the cutting process. • Hardness was tested for comparison of the web heights. This thesis shows that bending increased as webs became thinner and that bending occurred toward the wire as the second side of the web was cut. Bending does affect the height of the web. Physical properties of materials also impacted the height of the web with the hardest material staying intact during the cutting process. This study shows that two factors, physical properties of materials and web thickness, significantly affect cutting results for thin web parts.

Many phenomena determining the microstructure of a tool steel and consequently the properties of the material, are governed by multicomponent diffusion. The diffusion driven reactions that take place during, for example, tempering of a hot-work tool steel or when the microstructure develops during hot isostatic pressing of cold-work tool steel, are dependent on the types and amounts of alloying elements. In order for computational methods to be usable, these alloying effects need to be understood and incorporated in the models. In this work the influence of some typical tool steel alloying elements on the coarsening behavior of precipitates is investigated. Experimental coarsening studies are performed and the impact of the diffusion mobility descriptions and the thermodynamic descriptions are investigated by means of DICTRA coarsening calculations. The kinetic descriptions for diffusion in the body centered-cubic phase in the case of the chromium-iron-vanadium system and the chromium-iron-molybdenum system are improved by assessments of diffusion mobility parameters, and are shown to have a large impact on the calculated coarsening rate for vanadium-rich and molybdenum-rich precipitates. The effect of cobalt is examined by a coarsening experiment for vanandiumrich carbides and by a diffusion couple experiment for the investigation of the vanadium interdiffusion. The presence of cobalt is experimentally shown to have retarding effect on the coarsening rate of the carbides, but not on the vanadium diffusion. The coarsening rate of nitrogen-rich precipitates is compared to the coarsening rate of carbon-rich precipitates, and a lower coarsening rate for nitrides compared to carbides can be confirmed. Correlation between coarsening calculations and experiments is obtained suggesting that the thermodynamic description of the two systems is the underlaying reason for the different coarsening rates. Further, calculations utilizing the DICTRA software are combined with experimental investigations in order to study the possibility to apply computational methods for compound material development and explore application areas for high nitrogen alloyed tool steels produced by powder metallurgy. / <p>QC 20121011</p>

Today, there is a high demand on clean steel for high performance materialproperties. Thus, steel producers try to deliver a steel product with the highestquality and cleanliness to the market. The number of parameters that affect thesteel cleanliness may vary depending on the required material properties of thefinal product. However, the non-metallic inclusion characteristics represent one ofthe most important parameters. More specifically, the composition, size, numberand morphology affect steel cleanliness. In this work, selected parameters affectingthe inclusion characteristics were studied using the following methods: i)thermodynamic calculations (including computational thermodynamiccalculations), ii) inclusion determinations using a cross sectional (CS) method (2Dinvestigations) and iii) inclusion determinations using an electrolytic extraction(EE) method (3D investigations). The computational thermodynamic calculations of the slag-steel and inclusion-steelequilibriums were carried out using the Thermo-Calc software. With the help ofthese calculations, the influence of the slag carryover on the top slag, aluminumcontent in steel and sulfur distribution ratio as well as predictions of stable phasesof inclusions were studied. In addition, inclusion determinations of tool steel gradesamples collected during various stages of the ladle treatment in a scrap-based steelplant were carried out using both 2D and 3D methods. Furthermore, inclusiondeterminations of bearing steel grade samples from a runner system after ingotcasting were performed using a 2D metallographic method (CS-method). Also, theINCAFeature software was used, when using cross sectional method, in order tocollect more statistics of the inclusion characteristics. It was found that slag carryover has a large influence on the composition of theactual top slag as well as the aluminum content in the steel as well as the sulfurdistribution ratio. In addition, steel and slag were found to be in “near”-equilibriumconditions, after the completion of the vacuum degassing operation. Furthermore,the composition of small-size inclusions in samples taken from tool steel was foundto be very scattered. Moreover, the composition of the large-size inclusions wasfound to be less scattered. Furthermore, closer to the top slag composition insamples collected after vacuum degassing. Finally, the accuracy of the inclusioncomposition determinations of tool steel samples using the electrolytic extractionmethod was found to be better than for the cross sectional method. The worseaccuracy of the CS-method is due to a considerable effect of matrix elements oninclusion composition. / QC 20100709

Performance of indexable insert cutting tools is not only about the performance of cutting inserts. It is also about the cutting tool body, which has to provide a secure and accurate insert positioning as well as its quick and easy handling under severe working conditions. The common damage mechanisms of cutting tool bodies are fatigue and plastic deformation. Cutting tools undergo high dynamic stresses going in and out cutting engagement; as a result, an adequate level of fatigue strength is the essential steel property. Working temperatures of tool bodies in the insert pocket can reach up to 600°C, why the tool steel requires high softening resistance to avoid plastic deformation. Machinability is also essential, as machining of the steel represents a large fraction of the production cost of a cutting tool. The overall aim of the study is to improve the tool body performance by use of an advanced steel grade with an optimized combination of all the demanding properties. Due to the high-temperature conditions, the thesis concerns mostly hot-work tool steels increasing also the general knowledge of their microstructure, mechanical properties and machinability. Knowing the positive effect of sulphur on machinability of steels, the first step was to indentify a certain limit of the sulphur addition, which would not reduce the fatigue strength of the tool body below an acceptable level. In tool bodies, where the demand on surface roughness was low and a geometrical stress concentrator was present, the addition of sulphur could be up to 0.09 wt%. Fatigue performance of the cutting tools to a large extent depended on the steel resistance to stress relaxation under high dynamic loading and elevated temperatures. The stress relaxation behaviour, material substructure and dislocation characteristics in low-alloyed and hot-work tool steels were studied using X-ray diffraction under thermal and mechanical loading.  Different tool steels exhibited different stress relaxation resistance depending on their microstructure, temper resistance and working temperature. Hot-work tool steels showed to be more preferable to low-alloyed tool steels because of their ability to inhibit the rearrangement and annihilation of induced dislocations. High-temperature softening resistance of the hot-work tool steels was investigated during high-temperature hold-times and isothermal fatigue and discussed with respect to their microstructure. Carbide morphology and precipitation were determined using scanning and transmission electron microscopy. Machinability of a prehardened hot-work tool steel of varying nickel content from 1 to 5 wt% was investigated in end milling and drilling operations. Machining the higher nickel containing steels resulted in longer tool life and generated lower cutting forces and tool/workpiece interface temperature. The difference in machinability of the steels was discussed in terms of their microstructure and mechanical properties.

The focus of this literary study was additive manufacturing (AM) and the purpose was to find general trends for selected materials that have been additively manufactured and compare them to results from other reviews. The raw materials studied were stainless steels 316L, 17-4 PH, 15-5 PH and 420, as well as tool steel H13 and nickel alloys 625, 718 and Hastelloy X.The AM techniques studied were selective laser melting (SLM), electron beam melting (EBM) and binder jetting (BJG).  A total of 69 articles have been studied to fulfill the purpose above. The articles were used to write a summary of the techniques, compare them to each other and to conventional methods. They were also used to create a database to compile information on mechanical properties, microstructure and process parameters. Based on the database mechanical properties for SLM tend to be higher compared to EBM. This however varied somewhat depending on the processed material. Furthermore the yield and tensile strength obtained from the database for SLM seemed to be higher compared to the values in review articles for almost all materials. Unfortunately not enough values were found for BJG to compare it to SLM and EBM.AM seems to produce weaker, equal and superior products compared to conventional methods. However due to the limited nature of the project and the research found no conclusions can be drawn about any trends, how to achieve the different results or how parameters affect the finished product. To be able to say anything with more certainty more research has to be done. Not only in general concerning the AM techniques, but more studying of existing articles is needed. Finally a standardization on how to reference properties and process parameters is necessary. Currently it is very difficult to compare results or draw conclusions due to different designations, units and a lot of missing essential information.