Technologies of Coatings and Surface Hardening for Tool Industry

The innovative coating and surface hardening technologies developed in recent years allow us to obtain practically any physical–mechanical or crystal–chemical complex properties of the metalworking tool surface layer. Today, the scientific approach to improving the operational characteristics of the tool surface layers produced from traditional tools industrial materials is a highly costly and long-lasting process. Different technological techniques, such as coatings (physical and chemical methods), surface hardening and alloying (chemical-thermal treatment, implantation), a combination of the listed methods, and other solutions are used for this. This edition aims to provide a review of the current state of the research and developments in the field of coatings and surface hardening technologies for cutting and die tools that can ensure a substantial increase of the work resource and reliability of the tool, an increase in productivity of machining, accuracy, and quality of the machined products, reduction in the material capacity of the production, and other important manufacturing factors. In doing so, the main emphasis should be on the results of the engineering works that have had a prosperous approbation in a laboratory or real manufacturing conditions

Residual stress effects and damage tolerance behaviour of integral lightweight structures manufactured by FSW and HSM

Estágio realizado na empresa Airbus Operations GmbH, orientado pelo Mr. Marco PacchioneTese de Programa Doutoral. Engenharia Mecânica. Universidade do Porto. Faculdade de Engenharia. 201

Nanostructured Multilayer Ceramic Coatings for Wood-Cutting Tools

Lo sviluppo di questo dottorato di ricerca è stato supportato e finanziato dal progetto europeo Interreg ITA-SLO NANOREGION. La missione del progetto NANOREGION consiste nel costituire un consorzio tra università ed enti di ricerca locali atti a fornire una piattaforma scientifica di supporto alle imprese del territorio comprensivo delle regioni dell'Italia nord-orientale e la Slovenia. In tali regioni, l'impatto economico-sociale dell'industria del legno è rilevante. È noto che nella manifattura di materiali legnosi la necessità di una frequente sostituzione degli utensili da lavorazione, necessaria a garantire gli standard di qualità del prodotto finito, ha un forte impatto sull'economia del processo di lavorazione. Gli utensili da taglio sono generalmente protetti con rivestimenti a film sottile costituiti da materiali duri e refrattari per aumentarne la durabilità, riducendo la frequenza di sostituzione e quindi aumentando la produttività delle aziende. Tuttavia, a causa della natura del legno come materiale da lavorazione e dei rigorosi requisiti tecnici specifici della lavorazione del legno, il rapporto costi/benefici del processo di rivestimento degli utensili si è finora dimostrato non sufficiente a giustificare i costi addizionali legati al processo di rivestimento. Questo risulta in una minore penetrazione nel mercato degli utensili rivestiti rispetto a quanto accade invece nell'industria metalmeccanica. Un'eccezione, seppure in misura limitata, è rappresentata dai rivestimenti a base di cromo, come il nitruro di cromo (CrN), che forniscono la massima protezione contro l'usura dovuta a processi di corrosione. Questi, infatti, sono riconosciuti come una delle principali cause di usura nella lavorazione del legno, favorendo la successiva usura abrasiva dei fragili prodotti d’ossidazione operata da inclusioni di minerali duri presenti all'interno di materiali a base legnosa, soprattutto prodotti secondari già sottoposti a lavorazioni precedenti. Tuttavia, a causa della relativamente bassa durezza, il CrN fornisce di per sé una scarsa resistenza all'usura abrasiva. Una possibile soluzione consiste nel sostituire rivestimenti monostrato di CrN con rivestimenti multistrato. Ricerche e applicazioni pratiche approfondite hanno dimostrato che la progettazione di rivestimenti multistrato offre numerosi vantaggi rispetto ai rivestimenti a strato singolo, soprattutto se lo spessore degli strati costitutivi è ridotto al regime nanometrico. Tuttavia, la ricerca per lo sviluppo di rivestimenti multistrato mirati a rispondere ai severi requisiti dell'industria del legno è molto limitata. Pertanto, lo scopo di questo progetto di ricerca era di effettuare preliminari studi sulle proprietà protettive dei sistemi di rivestimento PVD multistrato a base di CrN accoppiato con nitruri di indurimento. L’abbinamento di proprietà anticorrosive e migliori caratteristiche meccaniche potrebbero rendere tali sistemi di rivestimento dei potenziali candidati per il rivestimento di utensili da taglio del legno. I nitruri di tungsteno e molibdeno (WN e MoN, rispettivamente) sono stati scelti in quanto già applicati per la realizzazione di sistemi multistrato con altri nitruri, e anche per fornire uno studio comparato su due sistemi che raramente vengono studiati in parallelo nelle stesse condizioni sperimentali. L'obiettivo fondamentale dell'aggiunta di questi materiali aggiuntivi è fornire al CrN una migliore durezza meccanica mantenendo o migliorando l'elevata resistenza alla corrosione, e la letteratura pregressa suggerisce ottime potenzialità di questi materiali come nitruri indurenti.The research activity of this Ph.D. thesis is grounded is founded by the European Interreg ITA-SLO NANOREGION project. The mission of NANOREGION was to provide a scientific support to local enterprises in the region comprehending North-eastern Italy and Slovenia. In such regions the impact of the wood-industry on local economics is relevant. It is well known that the impact of tools replacement has a strong impact on the economics of the wood-working process to maintain the manufacturing standards required to obtain high quality products. Cutting tools are usually coated with hard, refractory thin film coatings to increase their service life and hence increase the manufacture productivity. Nonetheless, owing to the nature of the wood as a workpiece and to the strict technical required specific of wood-machining, the cost-to-benefits ratio of tools coating has so far proved not enough to allow the same market penetration of coated tools that is instead recorded in the metal-working industry. An exception to some extent is represented by Chromium-based coatings such as CrN, which provide the highest protection against corrosive wear, which in turn is recognized as of the main causes of wear in wood-machining, as it favors the subsequent abrasive wear of the brittle oxidation products mediated by hard mineral inclusions within the wood-based materials. Nonetheless, CrN alone is known to provide poor resistance to abrasive wear, due to its relatively low hardness. A large amount of research has demonstrated that the design of multilayer coatings offers several advantages over single-layer coatings, especially if the thickness of the constituent layers is reduced to the nanometric regime. Nonetheless, the research investigating the development of multilayer coatings specifically targeting the strict requirements of the wood industry is very limited. Hence, the purpose of this research process was to investigate preliminary protective properties of multilayer PVD coating systems based on oxidation-protective CrN coupled with hardening nitrides as potential candidate coatings for wood-cutting tools. WN and MoN were chosen due to reported literature on successful coupling of such coatings with other nitrides such as TiN or ZrN and CrN, and because of the limited number of scientific and systematic comparative investigations on these systems. The fundamental aim of the addition of these additional materials is providing CrN with improved mechanical hardness while retaining or improving high corrosion resistance

Casting and Solidification of Light Alloys

Investigation of the effect of casting and crystallization on the structure and properties of the resulting light alloys and, in particular, research connected with detailed analysis of the microstructure of light alloys obtained using various external influences of ultrasonic, vibration, magnetic, and mechanical processing on the casting and crystallization are discussed. Research on the study of introduction of additives (modifiers, reinforcers, including nanosized ones, etc.) into the melt during the crystallization process, the technological properties of casting (fluidity, segregation, shrinkage, etc.), the structure and physicomechanical properties of light alloys are also included

Crystal Plasticity (Volume II)

With the second volume, we continue our mission to providing theoretical and experimental research that contribute new insights and practical findings in the field of crystal plasticity-related topics. Once again, a completely new set of 26 original works (including 22 research articles, 3 communications, and 1 review) has been collected. As in the case of the first volume, here, a full spectrum of topics belonging to the field of crystal plasticity is represented, including both numerical simulations and experimental works. By taking into account the investigated materials, the papers can be assigned to the following thematic groups: Steels and iron-based alloys; Non-ferrous alloys with fcc- (Ni- and Cu-based), or hcp crystal structure (Mg- and Ti-based). Other examples include Zirconium, Bi-Sn alloy, or polycarbonate resins; Multicomponent and high-entropy alloys; General theoretical studies on crystal plasticity. Specifically, the reprint should be interesting for students of material science and engineering, Ph.D. candidates, and researchers dealing with various theoretical and practical aspects of plastic deformation in crystalline materials

In situ analysis of PCBN cutting tool materials during thermo-mechanical loading using synchrotron radiation

Polycrystalline cubic boron nitride (PCBN) has outstanding properties in terms of hardness and chemical stability at elevated temperatures. Therefore, PCBN is used in cutting tool materials for hard machining applications e.g. hard turning of hardened steels. Due to the hardness of the workpiece, high forces act on a low contact area between tool and workpiece. Hence, severe thermo-mechanical loadings occur in such applications causing enhanced tool wear. Fundamental knowledge about the material behavior of PCBN-cutting-materials under thermo-mechanical loading is valuable as a basis for a better understanding of tool wear and finally for improvement of tool wear behavior. PCBN-materials are polycrystalline multi-phase compounds with strongly deviating material properties. In order to investigate the phase selective thermo-mechanical behavior of such materials lattice strain measurements are conducted under thermo-mechanical load using in situ X-ray diffraction with high energy synchrotron radiation. A four point bending test set-up and ceramic thermal heaters are used for the application of thermo-mechanical loading. Three different materials are investigated: a solid low PCBN-content material, a low PCBN-content material on a cemented carbide (CC) substrate and a high PCBN-content material on a CC-substrate. The low PCBN-content material exhibits a single phase binder material whereas the high PCBN-content material exhibits a multi-phase binder with up to five phases. Residual stresses are found in the samples with CC-substrate, only. Different phases of one material show different strains but nearly same stresses upon loading. Thus, thermo-mechanical loading can be seen as superposition of the respective mechanical and thermal loads. The space-resolved experimental data is used to validate an analytical model for the calculation of macroscopic stresses. The phase selective space-resolved strain and stress analysis presented in this paper provides a valuable method for the investigation and optimization of hard cutting tool materials and coatings under real cutting conditions