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Influence of the tool surface micro topography on the tribological characteristics in metal cutting – part I Experimental observations of contact conditions
Högskolan Dalarna, materialvetenskap. (Tribomaterial)
(English)Article in journal (Other academic) Submitted
Abstract [en]

The influence of surface micro topography of CVD α-Al2O3 coatings, deposited on cemented carbide inserts, on tribological characteristics in sliding contact and in metal cutting has been investigated using quenched and tempered steel as counter/work material. Pin-on-disc and turning tests were carried out and post-test characterization using 3D optical surface profilometry and scanning electron microscopy was performed in order to investigate the tribological response of the coatings. The results show that surface micro topography can have a significant impact on the tribological performance of Al2O3 coatings under initial and cutting contact conditions. For both kinds of tests the tendency for transfer of workpiece material strongly increases with increasing coating micro topography. In the pin-on-disc tests a smooth coating surface significantly reduces the friction coefficient.  In the turning tests the contact conditions at the flank face increases with decreasing micro topography. In contrast, no general conclusions can be drawn regarding the influence of coating micro topography on the contact conditions at the rake face. The resulting topography of the turned surface was found to increase with increasing coating topography.

Keyword [en]
CVD, α-Al2O3, topography, friction, sliding contact, metal cutting.
National Category
Materials Engineering
URN: urn:nbn:se:uu:diva-173170OAI: oai:DiVA.org:uu-173170DiVA: diva2:516816
Available from: 2012-04-19 Created: 2012-04-19 Last updated: 2012-08-01
In thesis
1. Microstructural, Mechanical and Tribological Characterisation of CVD and PVD Coatings for Metal Cutting Applications
Open this publication in new window or tab >>Microstructural, Mechanical and Tribological Characterisation of CVD and PVD Coatings for Metal Cutting Applications
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis focuses on characterisation of microstructure and the resulting mechanical and tribological properties of CVD and PVD coatings used in metal cutting applications. These thin and hard coatings are designed to improve the tribological performance of cutting tools which in metal cutting operations may result in improved cutting performance, lower energy consumption, lower production costs and lower impact on the environment.  In order to increase the understanding of the tribological behaviour of the coating systems a number of friction and wear tests have been performed and evaluated by post-test microscopy and surface analysis. Much of the work has focused on coating cohesive and adhesive strength, surface fatigue resistance, abrasive wear resistance and friction and wear behaviour under sliding contact and metal cutting conditions.

The results show that the CVD deposition of accurate crystallographic phases, e.g. α-Al2O3 rather than κ-Al2O3, textures and multilayer structures can increase the wear resistance of Al2O3. However, the characteristics of the interfaces, e.g. topography as well as interfacial porosity, have a strong impact on coating adhesion and consequently on the resulting properties.  Through the deposition of well designed bonding and template layer structures the above problems may be eliminated.

Also, the presence of macro-particles in PVD coatings may have a significant impact on the interfacial adhesive strength, increasing the tendency to coating spalling and lowering the surface fatigue resistance, as well as increasing the friction in sliding contacts.

Finally, the CVD-Al2O3 coating topography influences the contact conditions in sliding as well as in metal cutting.

In summary, the work illuminates the importance of understanding the relationships between deposition process parameters, composition and microstructure, resulting properties and tribological performance of CVD and PVD coatings and how this knowledge can be used to develop the coating materials of tomorrow.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 83 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 934
Tribology, Friction, Wear, Coatings, CVD, PVD, Alumina, Metal cutting
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Tribo Materials
urn:nbn:se:uu:diva-172364 (URN)978-91-554-8371-5 (ISBN)
Public defence
2012-06-08, Claes Ohlsson-salen, Skomakargatan 1, Borlänge, 10:00 (Swedish)
Available from: 2012-05-15 Created: 2012-04-05 Last updated: 2012-08-01Bibliographically approved

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Fallqvist, Mikael
Materials Engineering

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