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Analysis of lifetime of the cold forging tool with PVD coatings


  The main goal of the presented research is to reach the best balance between the cost of forging tools and their performance by apply- ing nanocomposite coatings providing low friction coefficient and optimum surface properties, which will help to achieve important increased in tool durability and high forging precision. The tribological tests with ball on disc (T10) tester and industrial tests of forging tool durability were made for the following PVD coatings: TiN (reference coating), TiAIN, nACVIc, TiCN-NP-MOVIC, TiC, TiCN-CBC and CrN-CBC2. SEM-EDAX microanalyser, TEM, Calotest and Rockwell diamond cone indentation/scratching performed were applied to study of coating nanomicrostructures. The differences in coatings structure leads to the change of the coating tribology behavior. The CrN-CBC2 and nACVIc nanocomposite coatings are characterized by significantly less value of the friction coefficient (0.1-0.2) as compared to other coatings under the same test conditions that results in its better durability. The present research was carried out in the frame of EUROSTARS Project NEGFORT. Głównym celem przedstawionych badań jest uzyskanie równowagi pomiędzy kosztem wytwarzania narzędzi kuźniczych oraz ich właściwościami użytkowymi, poprzez zastosowanie powłok nanokompozytowych, które pozwolą na uzyskanie niskiego współczynnika tarcia i optymalnych właściwości powierzchni. Pomoże to osiągnąć polepszoną wytrzymałość narzędzi oraz dużą dokładność kucia. Przeprowadzono testy tribologiczne na testerze kulka-dysk (T10) oraz testy przemysłowe wytrzymałości narzędzi kuźniczych z następującymi powłokami PVD: TiN (powłoka referencyjna), TiAIN, nACVIc, TiCN-NP-MOVIC, TiC, TiCN-CBC oraz CrN-CBC2. W celu zbadania nano- i mikrostruktury powłok, przeprowadzono analizy z wykorzystaniem: mikroanalizatora SEM-EDAX, TEM, Calotest oraz badanie twardości metodą Rockwella a także próbę zarysowań. Różnice w strukturze powłok powodują zmiany w ich właściwości tribolo[...]

Self-lubricanting cold forging tools

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In recent years, larger, more complex parts have been successfully cold forged due to improvements in forming equipment, die and workpiece materials, die coatings, and process design. In addition to the savings in energy costs, modern cold forging enables parts to be produced to near net shape [1]. Working conditions of forging tools have become severer with the years and it has been required for forging tools used to this end to increase the hardness, wear resistance and heat resistance. A typical shape of the tools exhibits an assembling in which a Cemented Carbides (CC) or High Speed Steel Insert (HSS) mounted into the casing. In these CC and HSS tools, the surface of the insert is ordinarily coated by CVD/PVD methods [2]. Many factors influence component accuracy in the form of systematic and random dimensional errors in the cold forming processes. There are four important factors that affect the component systematic errors, i.e.: imperfection of the material plastic flow, elastic deformation of the press system, elastic–plastic deformation and thermal behaviour of the tools and component [3]. The later two factors are most important and relevant to process and tool design of formed components. These effects become evident during different stages in the cold forming process, typically including forming, unloading, ejection and cooling. The repetitive production cycles in the industrial practice will bring further issues of dimensional changes due to tool wear and temperature increase developed over time. Thus, the tool wear resistance is one of the most important requirements.[...]

Deformation behaviour of 2017 nanostructured aluminium alloy

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The bulk nanostructured materials are attractive for various structural applications in the aerospace and automobile industries due to significant improvements in mechanical properties. They are usually produced in the top-down approach by severe plastic deformation (SPD) processes such as hydrostatic extrusion, equal channel angular pressing, high pressure torsion, accumulative roll bonding, cyclic extrusion-compression [1÷4]. SPD hydrostatic extrusion processes are particularly attractive for commercial applications because there is necessity for rivets and other parts manufacturing in aerospace industry. The hydrostatic extrusion has been shown to produce nanocrystalline (NC) and ultrafine grained (UFG) structures in titanium, Al-alloys, Cu and Cu-alloys, iron, austenitic steel, and nickel [1, 5÷8]. Precipitation hardening Al alloys (2XXX, 6XXX, and 7XXX series) are an important class of materials due to their perfect exploitation and technological properties. The components made of 2017 and 2117 alloys are the most widely used in aircraft construction because they have a high-strength and they are suitable for use with aluminium alloy structures. The nanostructured screw-bolts develop a greater shear strength than regular 2017 ones and are believed to be used in locations where extra strength is required. The precipitation hardening Al alloys offer possibilities for achieving high strength and ductility through SPD nanostructuring and subsequent heat treatment approach [9]. Recent studies indicate that the SPD processing at room temperature (RT) of precipitation hardening Al-Mg-Si alloy (in supersaturated condition) resulted in strain-induced precipitation of second phase particles due to the large number of defects generated during deformation and consequently higher density of nucleation sites [10]. However, the formability of such materials is generally poor due to their limited ductility, and processing technology opti[...]

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