248 research outputs found

    Face milling of nickel-based superalloys with coated and uncoated carbide tools

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    SIGLEAvailable from British Library Document Supply Centre-DSC:DXN036600 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

    The critical raw materials in cutting tools for machining applications: a review

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    A variety of cutting tool materials are used for the contact mode mechanical machining of components under extreme conditions of stress, temperature and/or corrosion, including operations such as drilling, milling turning and so on. These demanding conditions impose a seriously high strain rate (an order of magnitude higher than forming), and this limits the useful life of cutting tools, especially single-point cutting tools. Tungsten carbide is the most popularly used cutting tool material, and unfortunately its main ingredients of W and Co are at high risk in terms of material supply and are listed among critical raw materials (CRMs) for EU, for which sustainable use should be addressed. This paper highlights the evolution and the trend of use of CRMs) in cutting tools for mechanical machining through a timely review. The focus of this review and its motivation was driven by the four following themes: (i) the discussion of newly emerging hybrid machining processes offering performance enhancements and longevity in terms of tool life (laser and cryogenic incorporation); (ii) the development and synthesis of new CRM substitutes to minimise the use of tungsten; (iii) the improvement of the recycling of worn tools; and (iv) the accelerated use of modelling and simulation to design long-lasting tools in the Industry-4.0 framework, circular economy and cyber secure manufacturing. It may be noted that the scope of this paper is not to represent a completely exhaustive document concerning cutting tools for mechanical processing, but to raise awareness and pave the way for innovative thinking on the use of critical materials in mechanical processing tools with the aim of developing smart, timely control strategies and mitigation measures to suppress the use of CRMs

    Performance evaluation of uncoated and multi layer TiN coated carbide tool in hard turning

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    Hard coatings are well known to improve the performance of cutting tools in machining applications, such as high-speed machining and machining of MMC etc. Unfortunately, the development of cutting tool for high-speed machining of hard and difficult-to-cut material has remain a problem for quality and economy of production. The present work studies the performance of multi layer coated tool in machining of hardened steel ( AISI 4340 steel ) under high speed turning and compared with that of uncoated tool. Also the soft aluminium and soft and abrasive (Al+5% Si) were turned using CNC lathe. The influence of cutting parameters (speed, feed, and depth of cut) on cutting forces, surface finish and tool wear has been analyzed. Under the different cutting conditions, forces were measured both for coated and uncoated tools. For coated tools the forces obtained of resulted in relatively low values. For comparison, uncoated tool was also tested under the similar cutting conditions. The surface roughness of the workpieces were found out using Taylor Hobson (Surtronic 25) Surface Roughness Tester. Tool wear measurements demonstrate the capability of such tools in turning hard materials with reasonable tool life. The wear mechanism at the end of tool life was investigated in detail using scanning electron microscope (SEM). It has also been found that the machining of hard materials at higher speeds and lower feeds is improved by using coated tools as compared to uncoated tools. Turning with coated tool is more economical than the uncoated in terms of energy and power requirements

    Nano to micrometric grain sized CVD diamond for turning hard and abrasive materials

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    Doutoramento em Ciência e Engenharia de MateriaisO presente trabalho consistiu no desenvolvimento de ferramentas de corte de diamante CVD (Chemical Vapour Deposition) obtido na forma de revestimento em materiais cerâmicos à base de nitreto de silício monolítico (Si3N4) ou compósitos nitreto de silício-nitreto de titânio (Si3N4-TiN). A adição de TiN acima de 23 vol.% conferiu conductividade eléctrica ao compósito, na ordem de 1×10-1 W−1.cm-1, possibilitando a sua maquinagem por electroerosão. Duas técnicas foram utilizadas para o crescimento dos filmes de diamante: deposição química em fase vapor por plasma gerado por microondas, MPCVD (Microwave Plasma Chemical Vapour Deposition), e por filamento quente, HFCVD (Hot Filament Chemical Vapour Deposition). Previamente os substratos cerâmicos sofreram uma preparação superficial por diversos métodos: rectificação por mós diamantadas; polimento com suspensão de diamante (15μm); ataque da superfície por plasma de CF4; riscagem manual ou por ultra-sons com pó de diamante (0.5-1.0 μm). A caracterização das ferramentas revestidas envolveu: o estudo da qualidade e tensões residuais dos filmes de diamante a partir da difracção dos raios X e espectroscopia Raman; a análise da respectiva microestrutura e medida da espessura por microscopia electrónica de varrimento (SEM); a determinação dos valores de rugosidade dos filmes por microscopia de força atómica (AFM); e a avaliação da adesão dos filmes aos substratos por indentação com penetrador Brale. Foram obtidos filmes com granulometria que variaram da gama do diamante nanométrico (< 100 nm) até ao micrométrico convencional (3-12 μm), com consequências na rugosidade superficial do filme. Os filmes de diamante CVD apresentaram espessuras de 15 a 150μm. Os revestimentos apresentaram elevada adesão ao substrato, sendo que o melhor resultado foi atingido pelo diamante micrométrico, suportando um limite de carga aplicada de até 1600 N. O estudo do comportamento em serviço das ferramentas foi efectuado na operação de torneamento de metal duro (WC-Co) e de eléctrodos de grafite, com medição de forças de corte em tempo real por meio de um dinamómetro. Os ensaios foram realizados num torno CNC, em ambiente industrial, na empresa Durit (Albergaria-a-Velha), produtora de metal duro. Os modos de desgaste das ferramentas foram avaliados por meio de observação em microscopia óptica e electrónica de varrimento e o grau de acabamento da superfície maquinada por rugosimetria. A influência destes parâmetros foi estudada em termos das forças envolvidas em operações de torneamento, desgaste das ferramentas e do acabamento conferido à peça maquinada. Os melhores resultados do torneamento de metal duro foram atingidos pelas ferramentas com geometria de aresta em quina-viva, recobertas com os filmes de diamante de 100-200 nm de tamanho de grão, correspondentes às menores forças de corte (<150N), melhor qualidade da peça maquinada (rugosidade aritmética igual a 0,2 μm) e menor desgaste (flanco igual a 110μm). No torneamento de eléctrodos de grafite, as forças de corte foram baixas (< 20N), sendo que o principal modo de desgaste foi a formação de cratera na superfície de ataque (valor máximo igual a 22 μm). O fio da aresta de corte permaneceu inalterado (devido ao mínimo desgaste de flanco), sendo que as diferentes granulometrias do diamante não tiveram influência significativa no comportamento geral das ferramentas.This work consisted on the development of CVD (Chemical Vapour Deposition) diamond cutting tools directly deposited on monolithic silicon nitride (Si3N4) based ceramics and silicon nitride-titanium nitride composites (Si3N4-TiN). A TiN content higher than 23 vol.% confers electric conductivity to the composite in the order of 1×10-1 W−1.cm-1, making possible its machinability by means of electrodischarge machining. Two techniques were used for diamond growth: Microwave Plasma Chemical Vapour Deposition (MPCVD) and Hot Filament Chemical Vapour Deposition (HFCVD). The substrate pre-treatment steps prior to diamond deposition were: grinding with diamond wheels; polishing with diamond suspension (15μm); chemical etching with CF4 plasma; manual scratching or ultrasonic bath scratching with diamond powder (0.5-1.0 μm) for seeding purposes. The diamond cutting tools characterization involved: study of the quality and the residual stress of the films by X ray diffraction and Raman spectroscopy; analysis of respective film microstructure and measurement of film thickness by scanning electron microscopy (SEM); quantification of film surface roughness by atomic force microscopy (AFM); evaluation of adhesion strength of the thin films to Si3N4 substrate by the indentation technique with a Brale indenter. The grain size of the films varied from nanometric (< 100 nm) to conventional micrometric (3-12 μm), therefore giving different surface roughness. The CVD diamond film thickness was in the range of (15-150 μm). The diamond films presented a high adhesion level to the Si3N4 ceramic substrates, the best results being achieved by the micrometric grain sized film, which undergo a normal load of until 1600N. The study of the cutting tool behaviour was performed in turning operations of hardmetal (WC-Co) and graphite electrodes, by real-time acquisition of the cutting forces using a dynamometer. The turning operations were carried out in a CNC lathe, at industrial environment of a hardmetal producer company, Durit (Albergaria-a-Velha). The wear modes of the tested cutting tools were analysed by optical and electronic microscopy observations and the finishing quality of the machined workpiece was measured by surface roughness measurements. The influence of these parameters was studied in terms of the cutting forces developed during turning operations, of tool wear and of the finishing quality of the machined workpieces. The best results attained in hardmetal turning were achieved by the cutting tools with sharp edges, covered with diamond films of 100-200 nm of grain size, which presented the lowest cutting forces (<150N), the best workpiece surface quality (Ra=0.2μm) and the lowest flank wear (110μm). In graphite turning, the cutting forces were very low (<20N) and the main wear mode was the crater one on the rake face (maximum value of 22μm). The cutting edge remained almost intact (due to the minimum flank wear) while the different diamond grain sizes did not have a significant influence on the overall cutting behaviour

    A review on conventional and nonconventional machining of SiC particle-reinforced aluminium matrix composites

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    AbstractAmong the various types of metal matrix composites, SiC particle-reinforced aluminum matrix composites (SiCp/Al) are finding increasing applications in many industrial fields such as aerospace, automotive, and electronics. However, SiCp/Al composites are considered as difficult-to-cut materials due to the hard ceramic reinforcement, which causes severe machinability degradation by increasing cutting tool wear, cutting force, etc. To improve the machinability of SiCp/Al composites, many techniques including conventional and nonconventional machining processes have been employed. The purpose of this study is to evaluate the machining performance of SiCp/Al composites using conventional machining, i.e., turning, milling, drilling, and grinding, and using nonconventional machining, namely electrical discharge machining (EDM), powder mixed EDM, wire EDM, electrochemical machining, and newly developed high-efficiency machining technologies, e.g., blasting erosion arc machining. This research not only presents an overview of the machining aspects of SiCp/Al composites using various processing technologies but also establishes optimization parameters as reference of industry applications

    Advanced Powder Metallurgy Technologies

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    Powder metallurgy is a group of advanced processes used for the synthesis, processing, and shaping of various kinds of materials. Initially inspired by ceramics processing, the methodology comprising the production of a powder and its transformation to a compact solid product has attracted attention since the end of World War II. At present, many technologies are availabe for powder production (e.g., gas atomization of the melt, chemical reduction, milling, and mechanical alloying) and its consolidation (e.g., pressing and sintering, hot isostatic pressing, and spark plasma sintering). The most promising methods can achieve an ultra-fine or nano-grained powder structure, and preserve it during consolidation. Among these methods, mechanical alloying and spark plasma sintering play a key role. This book places special focus on advances in mechanical alloying, spark plasma sintering, and self-propagating high-temperature synthesis methods, as well as on the role of these processes in the development of new materials

    A review: drilling performance and hole quality of aluminium alloys for aerospace applications

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    Despite the growth of composites and other lightweight materials, aluminium alloys remain an attractive choice of the aerospace industry due to their mature manufacturing processes, good resistance to fatigue crack growth and superior damage tolerance. In the aerospace industry, the drilling process is the most challenging among all the other machining process as millions of holes are required for producing riveted and bolted joints in the assembly operation of the aircraft\u27s structures. The major challenges which arise from the drilling of these alloys are characterized by the poor hole quality which might initiate cracks within the airframe structure and reduces their reliability. This results in the rejection of parts at the assembly stage which directly impacts the manufacturing cost. Hence, appropriate selection of tool geometry, tool material and coatings, optimal cutting speed and feed rate, as well as drilling machines, is required to meet the requirement of machined parts. This motivates both academia and industries to further research on the application of drilling operations in the aircraft industry. This review aims to document details on drilling forces, drilling parameters, drill tool geometry, drill materials and coatings, chips formation, analysis of tool wear and hole metrics such as the hole size and circularity error, surface roughness, and burrs formation during the drilling of different aluminium alloys used in the aerospace industry. The focus will be mainly on Al2024 and Al7075 alloys since they are most commonly used and reported in the open literature
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