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Nanoindentation hardness, texture and microstructure of a-Al2O3 and ?-Al2O3 coatings
Seco Tools AB, S-737 82 Fagersta, Sweden.
Seco Tools AB, S-737 82 Fagersta, Sweden.
Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
2008 (English)In: Thin Solid Films, ISSN 0040-6090, Vol. 516, no 18, 5959-5966 p.Article in journal (Refereed) Published
Abstract [en]

Nanoidentation responses of Al2O3 coatings obtained using chemical vapour deposition on cemented carbides were studied and related to the Al2O3 modification and microstructure. Five different Al2O3 layers were studied: (i) ?-Al2O3, (ii) a-Al2O3, obtained through the ? ? a phase transformation, (iii) as-grown a-Al2O3 with (101-2) texture, (iv) as-grown a-Al2O3 with (101-4) texture and (v) as-grown a-Al2O3 with (0001) texture. All the Al2O3 coatings were deposited to a thickness of at least 6 µm onto identical WC - 6 wt.% Co cemented carbide substrates. Nanoindentation was performed on taper-section specimens. The microstructure, phase and texture were elucidated by using transmission electron microscopy, scanning electron microscopy and X-ray diffraction. Nanoindentation responses of the as-grown, textured a-Al2O3 coatings were compared with ?-Al2O3 and a-Al2O3 formed as a result of the ? ? a phase transformation. The as-grown, textured a-Al2O3 layers exhibited clearly a higher hardness and Young's modulus than the ?-Al2O3 and the a-Al2O3 layers formed as a result of the phase transformation. Only slight differences in hardness and modulus could be detected between the (101-2), (101-4) and (0001) textured a-Al2O3 films. Among these the (101-2) textured a-Al2O3 coating exhibited the lowest hardness and modulus. Opposite to earlier reports, the present investigation clearly showed that ?-Al2O3 exhibited both the lowest hardness and Young's modulus as compared with the other studied coatings. It is emphasised that the earlier nanoindentation investigations that were intended to deal with a-Al2O3 were in fact performed on transformed ?-Al2O3. © 2007 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
2008. Vol. 516, no 18, 5959-5966 p.
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-45700DOI: 10.1016/j.tsf.2007.10.078OAI: diva2:266596
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2011-01-10

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