1,720,991 research outputs found
Development of innovative TCT saw blades for high speed cutting of metallic alloys
Full text linkThe subject covered in this thesis concerns the development of an innovative PVD coated multipoint cutting tool with cemented carbide brazed inserts for high-speed cutting of ferrous alloys. The aim of the research was to optimize the properties of the constituent materials in order to maximize their durability and provide a constant level of surface finishing of the machined parts. Fast cutting technologies are nowadays spreading because of the high productive rate that they guarantee, but on the other side wear is more severe with high speed cutting. Tungsten Carbide Tipped (TCT) saw blades are typically used in wood cutting but since 30 years are gradually taking the place of traditional band saws due to the higher cutting speed that are possible to reach and thanks to a better surface finishing on machined surfaces. The research work that was part of an industrial project was divided into three steps:
1. characterization of cemented carbide grades for application in machining
2. optimization of the cutting geometry
3. development of a tailored CAE – PVD coating.
The first part of the research work involved the study of literature in order to define the most suitable grades of cemented carbide for experimentation and to define some possible coating composition and architectures. Both plain grades and mixed grades with secondary Ti and Ta carbides were chosen, the relations among hardness, toughness, grain size and wear resistance were investigated through microstructural and mechanical characterization; finally discs made of cemented carbide were tested against pins of steel to characterize the resistance to sliding wear. From this characterization a mixed grade cemented carbide with 12% cobalt binder and micrometric grain size was chosen due to the best toughness properties shown from characterization. Saw blades work under interrupted cutting conditions so toughness was required as the most important feature. In the second part of this study the cutting geometry of the cemented carbide inserts was optimized via experimental cutting tests and CAE methods. After a set of benchmark cutting tests on an industrial sawing station, the experimental cutting forces were calculated analytically and than used to calibrate a FEM 2D numerical calculation model. Two cutting geometries were then tested among those simulated: -15° and -25° rake angles. Thanks to the use of an hard metal with increased toughness (KIC> 15 MPa), a tool with a rake angle of -15 ° has been designed to guarantee lower cutting forces (less than 90 N in the first cuts), friction and temperature on the surface of the tool’s rake face (Figure 1). By experimental validation of the simulated geometries the cutting model gained predictive power. In the second phase of the work, three CAE - PVD coatings of the Al - Ti - Cr - N system were studied. Two of them were monolayer and one multilayer. The aim of this part of the work was to investigate the mechanical and microstructural properties of the analyzed coatings using different experimental methods to describe their behavior. The coatings were characterized not only from the mechanical point of view (hardness, toughness and adhesion) but also from the morphological (defective), and microstructural point of view. From the tests carried out, a multi-layered coating with improved toughness for use in interrupted cutting was designed
Study and Development of a Multilayered Coating to Improve Hard Metal Cutting Tools Performances
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Overview of heat treatment and surface engineering. Influences of surface finishing on hot – work tool steel
No full textDue to high resistance, toughness, formability and wear resistance
the use of both ferrous and non ferrous alloys is widespread in automotive,
tools and die manufacturing, high-temperature applications (engines, valves,
nozzles and turbines), oil/gas and energy production plants. The destructive
effects of wear, corrosion, high temperature working conditions and their
synergic action cost 100 billion Euros each year and most problems affect the
surface of a component. Die casting is characterised by harsh conditions for the
die which has to resist to all the damaging mechanisms proposed and molten
aluminium alloy is a potential corrosive environment for steel. Periodical
heating/cooling cycles can lead to thermal fatigue damaging of the die. In this
paper, the relation between the surface finishing of a hot – work tool steel used
in die casting industry and its damaging mechanism during service was
considered and studied
Focus on Carbide-Tipped Circular Saws when Cutting Stainless Steel and Special Alloys
No full textCircular saw blades are used exclusively for cut-off work, ranging from small manual feed operations, up to very large power fed saws commonly used for sectioning stock as it comes from a rolling mill or other manufacturing processes for long products. The teeth profile, as well as the tooth configuration are of fundamental importance for the blade performances; through a combination of blade rigidity and grinding wheel condition a good quality surface finish is attained for tools of commercial standard. The materials used for the production of circular saw blades are ranging from high speed steel to cemented carbides. In particular, cemented carbides, being characterized by high hardness and strength, are used in applications where materials with high wear resistance and toughness are required. The main constituents of cemented carbides are tungsten carbide and cobalt. Tungsten carbide imparts the alloys the necessary strength and wear resistance, whereas cobalt contributes to the toughness and ductility of the alloys. The WC-Co alloys are tailored for specific applications by the proper choice of tungsten carbide grain size and the cobalt content. The grain size of the tungsten carbide in WC-Co varies from about 40 μm to around 0.3 μm, the cobalt content from 3 to 30 wt%. The coarse grained hard metals are mainly used in mining applications, the smallest grain size being about 3 μm and the minimum cobalt content 6 wt%. The grain size of tungsten carbide in the metal cutting industry, as well as for universal applications lies in the range of 1-2 μm. However, with the advent of near net shape manufacturing and thin walled components, the use of submicron carbide is growing, since their high compressive strength and abrasive wear resistance can be used to produce tools with a sharp cutting edge and a large positive rake angle. In this paper, a general overview on the actual trends in the choice of the best material when cutting special alloys will be presented and discussed. Based on the recent and past literature some examples of their up-to-date application, such as circular saws used to cut stainless steels and some high strength alloys, are talk ove
Properties of UNS S32760 Duplex Stainless Steels Powders and L-PBF Components as Function of Different Processing Gases
Full text linkSuper duplex stainless steels (SDSS) combine the advantages of ferritic and austenitic steels and reach an excellent combination of mechanical and corrosion properties. The paper focuses on the production of UNS S32760 (X2CrNiMoCuWN25-7-4, AISI F55, 1.4501) SDSS powders through Vacuum induction melting Inert Gas Atomization (VIGA) with different gas atmospheres, Argon or Nitrogen. The effect of the different gases used during the melting and the atomizing on the characteristics of the final powder was investigated, in terms of granulometry, morphology, microstructure, chemical composition (also taking into account light elements such as N, O, H, C, and S). Powders were then processed by means of Laser Powder Bed Fusion (L-PBF) and microstructural features and mechanical properties of produced components were analyzed in the as processed state and after thermal treatments, properly optimized to obtain a good balancing between the α ferrite/austenite phases
Ultraviolet–Visible-Near InfraRed spectroscopy for assessing metal powder cross-contamination: A multivariate approach for a quantitative analysis
Full text linkThe last few years have seen an increasing use of spherical metals powders to produce bulk parts through metal forming technologies like Additive Manufacturing and Metal Injection Molding. This, coupled with the wide availability of metal powders, leads to a critical issue: contamination across different systems in different process steps. Consequently, it is necessary to find a new, fast, and reliable analysis sensible to tiny traces of contamination. This work evaluates the applicability of Ultraviolet–Visible-Near InfraRed (UV–Vis-NIR) spectroscopy, a technique providing information on powders’ reflectance, for studying contaminated powders. This work focuses on assessing 3 binary systems obtained from the cross-contamination of 3 components (A92618, C10200 and S31603) in a low contamination range (from 0.5 vol% to vol. 6%) and in a high contamination range (25 vol% and vol.50%). After the UV–Vis-NIR analysis, multivariate analysis has been used to obtain quantitative results. Results show that, as the contamination level increases in the binary system, the shape of spectra changes and becomes progressively more similar to the contaminant one. The chemometric analysis allows the detection of the contaminant type and its concentration percentage in the contaminated powder
CORRELAZIONE TRA LA FINITURA SUPERFICIALE E IL MECCANISMO DI DANNEGGIAMENTO PER ACCIAI DA STAMPO
No full textParametric modeling of cradle-to-gate carbon emissions from gas-atomized AISI 316L powders under closed-loop feedstock strategies
No full textThis study introduces a parametric framework for the cradle-to-gate assessment of carbon emissions associated with the production of gas-atomized AISI 316L stainless steel powders intended for use in additive manufacturing and other powder metallurgy processes. The model provides a detailed representation of upstream material flows and includes all major unit operations involved in powder production, such as feedstock preparation, gas atomization, sieving and blending, and packing. By varying the composition of the feedstock charged into the atomizer crucible, the framework enables the estimation of carbon emissions across a wide range of scenarios reflecting alternative sourcing strategies. The case study on AISI 316L highlights the environmental benefits of integrating closed-loop material flows, including the recirculation of off-specification powders and the direct use of compatible metallic scrap. Furthermore, broadening the acceptable powder size range significantly improves atomization yield, thereby reducing the specific carbon intensity of usable powder output. Such an approach lays the foundation for the development of robust decision-support tools for process planning in gas atomization, with direct implications for industrial-scale powder production
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