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Impact of nitrogen vacancies on the high temperature behavior of (Ti1-xAlx)N-y alloys
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. University of Saarland, Germany.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. SECO Tools AB, Sweden.ORCID iD: 0000-0003-4577-0976
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
University of Saarland, Germany.
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2016 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 119, p. 218-228Article in journal (Refereed) Published
Abstract [en]

Substoichiometric solid solution alloys of cubic (Ti1-xAlx)N-y with x = 0.26, 0.48 and 0.60, and y ranging from 0.93 to 0.75 were grown by cathodic arc deposition. The influence of nitrogen deficiency on their thermal stability was studied by X-ray diffractometry, differential scanning calorimetry, scanning electron microscopy, and atom probe tomography. The nitrogen deficiency did not significantly affect the columnar growth nor the as deposited hardness. At elevated temperatures, alloys with x = 0.48 and 0.60 decompose isostructurally into cubic c-TiN and cubic c-AlN domains, which is consistent with spinodal decomposition. The decomposition is retarded by decreasing the nitrogen content, e.g. the formed isostructural domains in (Ti0.52Al0.48)N-0.92 at 900 degrees C are similar in size to (Ti0.52Al0.48)N-0.75 at 1200 degrees C. The formation of hexagonal w-AlN is shifted to higher temperatures by decreasing nitrogen content. Nucleation and growth of Al-Ti clusters in a Ti rich matrix were observed for the alloys with high Ti content, x = 0.26. These results suggest that nitrogen deficiency reduces the driving force for phase separation. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD , 2016. Vol. 119, p. 218-228
Keywords [en]
TiAlN system; Nitrogen vacancies; Spinodal decomposition; Atom probe tomography; Thin films
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:liu:diva-132334DOI: 10.1016/j.actamat.2016.08.024ISI: 000384778300021OAI: oai:DiVA.org:liu-132334DiVA, id: diva2:1046208
Note

Funding Agencies|Erasmus Mundus doctoral program DocMASE; Swedish Research Council VR [621-2012-4401]; Swedish Foundation for Strategic Research, SSF via MultiFilms program [RMA08-0069]; Swedish government strategic research area grant AFM - SFO MatLiU [2009-00971]; VIN-NOVA (M - Era.net) [2013-02355(MC2)]; DFG; federal state government of Saarland [INST 256/298-1 FUGG]; AME-Lab (European Regional Development Fund) [C/4-EFRE-13/2009/Br]

Available from: 2016-11-12 Created: 2016-11-01 Last updated: 2018-01-03
In thesis
1. Defect-engineered (Ti,Al)N thin films
Open this publication in new window or tab >>Defect-engineered (Ti,Al)N thin films
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates the effect of point defects (nitrogen vacancies and interstitials) and multilayering ((Ti,Al)N/TiN) on the phase transformations in cathodic arc-evaporated cubic (Ti,Al)N thin films at elevated temperatures. Special attention is paid to the evolution of the beneficial spinodal decomposition into c-TiN and c-AlN, the detrimental formation of wurtzite AlN and the potential application as hard coating in cutting tools.

c-(Ti1-xAlx)Ny thin films with varying Al fractions and N content (y = 0.93 to 0.75) show a delay in the spinodal decomposition when increasing the amount of N vacancies. This results in a 300 °C upshift in the age hardening and a delay in the w-AlN formation, while additions of self-interstitials enhance phase separation. High temperature interaction between hard metal substrates and thin films is more pronounced when increasing N deficiency through diffusion of substrate elements into the film. Low N content films (y = 0.58 to 0.40) showed formation of additional phases such as Ti4AlN3, Ti2AlN, Al5Ti2 and Al3Ti during annealing and a transformation from Ti2AlN to Ti4AlN3 via intercalation. The multilayer structure of TiN/TiAlN results in surfacedirected spinodal decomposition that affects the decomposition behavior. Careful use of these effects appears as a promising method to improve cutting tool performance.

Abstract [de]

Diese Arbeit untersucht den Effekt von Punktdefekten (Stickstoffleerstellen und Zwischengitteratome) und Multilagen ((Ti,Al)N/TiN) auf die Phasenumwandlung in lichtbogenverdampften kubischen (Ti,Al)N-Dünnschichten bei erhöhten Temperaturen. Besonderes Augenmerk liegt auf der Entwicklung der vorteilhaften spinodalen Entmischung in c-TiN und c-AlN und der nachteiligen Bildung von Wurtzit-AlN, sowie der möglichen Anwendung als Hartstoffbeschichtung von Schneidwerkzeugen.

c-(Ti1-xAlx)Ny mit unterschiedlichem Al-Anteil und N-Gehalten von y = 0,93 bis 0,75 zeigt mit zunehmenden Stickstoffleerstellen eine Verzögerung der spinodalen Entmischung. Dadurch verschiebt sich die Ausscheidungshärtung um 300 °C zu höheren Temperaturen und die w-AlN-Bildung wird verzögert, während der Einbau von Eigenzwischengitteratomen die Entmischung beschleunigt. Die Hochtemperaturwechselwirkung zwischen Hartmetallsubstrat und Dünnschicht durch Diffusion von Substratelementen in die Schicht nimmt mit steigendem Stickstoffdefizit zu. Stickstoffarme Schichten (y = 0,58 bis 0,40) zeigen während der Wärmebehandlung zusätzliche Phasen wie Ti4AlN3, Ti2AlN, Al5Ti2 und Al3Ti und eine Umwandlung von Ti2AlN in Ti4AlN3 durch Interkalation. Die Multischichtstruktur von TiN/TiAlN führt zu einer oberflächengerichteten spinodalen Entmischung, die das Entmischungsverhalten beeinflusst. Ein gezielter Einsatz dieser Effekte erscheint als ein vielsprechender Weg, um die Leistungsfähigkeit von Schneidwerkzeugen zu verbessern.

Abstract [sv]

I denna avhandling behandlas inverkan av punktdefekter (kvävevakanser och interstitialer) och multilagring ((Ti,Al)N/TiN) på högtemperaturfasomvandlingar i tunna arcförångade skikt av kubiska (Ti,Al)N. Störst vikt har lagts på utvecklingen av det fördelaktiga spinodala sönderfallet till c-TiN och c-AlN, den ofördelaktiga omvandlingen till w-AlN och potentialen som hårda skikt i verktygstillämpningar.

Tunna c-(Ti1-xAlx)Ny skikt med olika Al-andel och en N-halt mellan (y = 0.93 och 0.75) uppvisar ökad undertryckning av det spinodala sönderfallet med ökat kvävevakanshalt. Detta resulterar i bildandet av w-AlN skiftas upp i temperatur vilket gör att åldershärdningen höjs med 300 °C. Däremot medför närvaron av självinterstitialer ett snabbare sönderfall. Växelverkan mellan hårdmetallsubstraten och de tunna skikten vid hög temperatur ökar med minskad kvävehalt i skiten genom diffusion av atomer från substratet in i filmen. Filmer med låg kvävehalt (y = 0.58 till 0.40) bildar även andra faser så som Ti4AlN3, Ti2AlN, Al5Ti2 och Al3Ti under värmebehandling och fasomvandlingen från Ti2AlN till Ti4AlN3 sker via en mekanism kallad intercalation. Multilagring av TiN/TiAlN resulterar i ett ytriktad spinodalt sönderfall vilket påverkar det totala sönderfallsförloppet. Nyttjande av dessa resultat syns som lovande vägar till förbättrade verktygsegenskaper.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. p. 73
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1878
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-142116 (URN)10.3384/diss.diva-142116 (DOI)9789176854563 (ISBN)
Public defence
2017-11-14, House D3 3, Saarland University, DE-66123 Saarbrücken, Germany, Saarbrücken, 14:15 (English)
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Available from: 2017-10-23 Created: 2017-10-23 Last updated: 2017-10-23Bibliographically approved

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Schramm, IsabellaJohansson Jöesaar, Mats P.Jensen, JensOdén, Magnus
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