Definierte strukturierte Hartmetallwerkzeuge für abrasive Prozesse

The challenge of this dissertation concerns the surface structuration of the WC-CoNi hardmetal with defined geometry, despite the fact that the embedded WC grains have irregular geometrical properties and distribution. An advanced method should be found and applied to structure the WC-CoNi hardmetal tool surface. The structured surfaces should be favorable and beneficial to reduce friction or to remove material in abrasive machining processes. Based upon the surface topography characterization of existing abrasive tools, e.g., CBN honing stone, geometrical properties of abrasives can be measured and quantified. The obtained geometrical information can contribute to the reproduction of the abrasive tool surface on WC-CoNi hardmetal. Laser surface texturing is an advanced machining method with high precision and it can effectively avoid some common thermal damage. Therefore, this method is implemented to machine WC-CoNi hardmetal surfaces. It is found that the structured WC-CoNi hardmetal tool can effectively remove material and improve surface quality of the counterpart (workpiece). These surface patterned hardmetal tools emerge then as potential alternative to conventional abrasive tools. Meanwhile, other patterns have also been produced on the hardmetals, and they can be used in the tribological system to reduce friction and improve wear resistance. It is a methodological and technical innovation to fabricate abrasive machining tools using laser to produce defined structures on a hardmetal surface, because it not only expands the utilization of hardmetal as an abrasive tool material but also enables the control and design of abrasive tool surface topography with high precision.Die Herausforderung dieser Arbeit besteht in der geometrischen Strukturierung von WC-CoNi-Hartmetall-Oberflächen, wobei die eingebetteten WC-Körner geometrische unbestimmte Eigenschaften sowie zufällige Verteilungen aufweisen. Es sollen neue Methoden gefunden und angewendet werden, um WC-CoNi Hartmetallwerkzeugoberflächen zu strukturieren. Mit Hilfe dieser Strukturen soll die Reibung reduziert oder Material durch abrasive Bearbeitung gezielt abgetragen werden. Durch eine geeignete Charakterisierung der Oberflächentopographie vorhandener Abrasivwerkzeuge können die geometrischen Eigenschaften von abrasiven Körnern ermittelt und quantifiziert werden. Die erworbenen geometrischen Informationen können zur Reproduktion der Oberflächen von Abrasivwerkzeugen auf Hartmetalloberflächen genutzt werden. Die Laseroberflächenstrukturierung ist ein innovatives Bearbeitungsverfahren mit hoher Präzision und Effizienz. Diese Methode kann wirksam die üblichen thermischen Schäden vermeiden. Daher ist dieses Verfahren zur Bearbeitung von WC-CoNi Hartmetall vorteilhaft. Es konnte bestätigt werden, dass die neuartigen strukturierten WC-CoNi Hartmetallwerkzeuge die Materialien der Werkstücke abtragen und die Oberflächenqualität dieser verbessern. Diese oberflächenstrukturierten Hartmetallwerkzeuge können als potentielle Alternative zu konventionellen abrasiven Werkzeugen dienen. Parallel hierzu wurden weitere Strukturmuster auf Hartmetalloberflächen erzeugt. Die Strukturen können in einem tribologischen System angewendet werden, um Reibung zu reduzieren und Verschleißbeständigkeit zu verbessern. Die definiert erzeugten Strukturen können nicht nur bei Hartmetallen als Schleifwerkzeugmaterial eingesetzt werden, sondern ermöglichen auch eine gezielte Einstellung der Werkzeugoberflächentopographie

Residual stress distribution in PVD-coated carbide cutting tools - origin of cohesive damage

PVD-coatings for cutting tools mean a substantial progress for tool lifetime and cutting conditions. Such tools, however, hold the risk of cost intensive sudden process breaks as a result of cohesive damage. This damage mechanism does not consist of a coating adhesion problem, but it can be traced back to the residual stress distribution in coating and substrate. This paper shows how residual stresses develop during the process chain for the manufacturing of PVD-coated carbide cutting tools. By means of different methods for residual stress determination it is shown that the distribution of residual stresses within the tool finally is responsible for the risk of cohesive tool damage.DFG/DE 447-50-

Remanufacturing and Advanced Machining Processes for New Materials and Components

"Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems.

Effect of Micro-blasting on Characteristics and Machining Performance of PVD AlTiN Coated Cutting Tools

It is essential to sustain ever increasing challenges faced by cutting tool manufacturers in improving the performance of the tools during machining of difficult-to-cut materials which have been developed in recent times. Although coated tools have found wide application in industries, there still remains a considerable scope of improvement of the properties of coatings with a view to achieve environment-friendly dry machining. Surface treatment has been identified as one of the possible avenues which has the potential to augment properties and performance of coated tools in dry machining. The current research work has utilized micro-blasting of cutting tool substrates prior to coating deposition as well as coated surface in order to recommend optimal surface treatment technique for the development of a coated tool. AlTiN coating is deposited using cathodic arc evaporation and effect of micro-blasting both as pre-treatment as well as post-treatment methodology is investigated on micro-structure, crystallographic orientation, grain size, coating adhesion and hardness. Effect of surface treatment has been finally studied during machining of 17-4 PH martensitic stainless steel. As-deposited AlTiN coating without any treatment has all along been considered for comparison. Results have clearly indicated micro-blasting as pre-treatment technique considerably enhances coating adhesion while post-treatment results in increase in hardness. Since both the properties are essential in combating coating delamination and improving wear resistance, AlTiN coating with both pre- as well as post-treatment techniques has demonstrated excellent promise in dry machining application. Significant reduction in cutting force up to 27% is observed using AlTiN coated tool subjected to both pre- and post-treatment. The same tool is also successful in bringing down in chip reduction co-efficient. While tool wear progression of only pre-treated and pre- as well as post-treated tools are similar under lower cutting speed (120 m/min), the latter clearly outperformed all the tools under higher cutting speed (150 m/min)

Remanufacturing and Advanced Machining Processes for New Materials and Components

Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems

Remanufacturing and Advanced Machining Processes for New Materials and Components

Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems

Remanufacturing and Advanced Machining Processes for New Materials and Components

"Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems.

Laser surface modification of biomedical alloys

This study investigated the effects of high speed laser surface modification on 316L stainless steel and Ti-6Al-4V for biomedical implants application. Laser processing was carried out in an inert argon environment using a 1.5 kW CO2 laser. Parameters investigated in this work included irradiance, residence time, pulse width and sample pre-treatments. Surface topology, microstructure and melt pool depth were characterised using the scanning electron microscope. White light interferometry and stylus profilometry were used to determine the surface roughness. X-ray diffractometry was used to investigate the crystallinity and phase transformation induced by the laser treatment. Micro-hardness was measured using a Vickers micro-hardness indentation apparatus. Wear behaviour was investigated using a pin on disk apparatus. Corrosion behaviour was evaluated using a potentiostat and an electrochemical cell set-up simulating human body conditions. Biocompatibility of the samples was investigated in vitro by monitoring NIH/3T3 fibroblast and MC3T3-E1 osteoblast cell growth via MTT and Hoechst DNA assays. A strong correlation between irradiance, residence time, depth of processing and roughness was established in 316L. High depth of altered microstructure and increased roughness were linked to higher levels of both irradiance and residence times. At fixed energy density, increase in residence time resulted in growth of the melt pool. In the melted region, a uniform composition in microstructure with fewer impurities was observed. In Ti-6Al-4V alloy, laser treatment resulted in crack-free layers, twenty to fifty microns thick. With increase in both irradiance and residence time, surface roughness was found to decrease while melt pool depth increased. A martensite structure formed on the laser treated region producing acicular αTi nested within the aged βTi matrix. The βTi phase volume fraction was reduced by up to 19%. Microhardness increased up to 760 HV0.05 which represented a 67% increase compared to the bulk material. A homogenous chemical composition of the alloying elements was achieved in laser modified regions. Much lower levels of wear were noted in laser treated samples compared to untreated samples. Stable passive polarisation behaviour and reduction in corrosion rates was noted in treated samples ranging between 86 and 239 nm yr-1 compared to 108 nm yr-1 for untreated samples and 309 nm yr-1 for grit blast samples. Direct contact assays showed that laser treated samples had improved cytotoxicity properties compared to their untreated counterparts