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High pressure and high temperature stabilization of cubic AlN in Ti0.60Al0.40N
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
University of Bayreuth, Germany .
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
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2013 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 5Article in journal (Refereed) Published
Abstract [en]

In the present work, the decomposition of unstable arc evaporated Ti0.6Al0.4N at elevated temperatures and quasihydrostatic pressures has been studied both experimentally and by first-principles calculations. High pressure and high temperature (HPHT) treatment of the samples was realized using the multi anvil press and diamond anvil cell techniques. The products of the HPHT treatment of Ti0.6Al0.4N were investigated using x-ray diffractometry and transmission electron microscopy. Complimentary calculations show that both hydrostatic pressure and high temperature stabilize the cubic phase of AlN, which is one of the decomposition products of Ti0.6Al0.4N. This is in agreement with the experimental results which in addition suggest that the presence of Ti in the system serves to increase the stability region of the cubic c-AlN phase. The results are industrially important as they show that Ti0.6Al0.4N coatings on cutting inserts do not deteriorate faster under pressure due to the cubic AlN to hexagonal AlN transformation.

Place, publisher, year, edition, pages
American Institute of Physics (AIP) , 2013. Vol. 113, no 5
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-90201DOI: 10.1063/1.4790800ISI: 000314746200028OAI: oai:DiVA.org:liu-90201DiVA: diva2:612359
Note

Funding Agencies|Swedish Foundation for Strategic Research (SSF)||German Research Foundation (DFG)|SPP 1236|

On the day of the defence day the status of this articla was Manucsript and title of this was High pressure and high temperature behavior of Ti0.60Al0.40N.

Available from: 2013-03-21 Created: 2013-03-21 Last updated: 2017-12-06
In thesis
1. Microstructural evolution of TiAlN hard coatings at elevated pressures and temperatures
Open this publication in new window or tab >>Microstructural evolution of TiAlN hard coatings at elevated pressures and temperatures
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A typical hard coating on metal cutting inserts used in for example turning, milling or drilling operations is TiAlN. At elevated temperatures, TiAlN exhibits a well characterized spinodal decomposition into coherent cubic TiN and AlN rich domains, which is followed by a transformation from cubic to hexagonal AlN. Using in-situ synchrotron x-ray radiation, the kinetics of the second transformation was investigated in this thesis and the strong temperature dependence on the transformation rate indicated a diffusion based nucleation and growth mechanism. The results gave additional information regarding activation energy of the transformation and the critical wavelength of the cubic domains at the onset of hexagonal AlN. After nucleation and growth, the hexagonal domains showed a striking resemblance with the preexisting cubic AlN microstructure.

During metal cutting, the tool protecting coating is subjected to temperatures of ~900 ºC and pressure levels in the GPa range. The results in this thesis have shown a twofold effect of the pressure on the decomposition steps. Firstly, the spinodal decomposition was promoted by the applied pressure during metal cutting which was shown by comparisons with annealed samples at similar temperatures. Secondly, the detrimental transformation from cubic to hexagonal AlN was shown to be suppressed at elevated hydrostatic pressures. A theoretical pressure/temperature phase diagram, validated with experimental results, also showed suppression of hexagonal AlN by an increased temperature at elevated pressures.

The spinodal decomposition during annealing and metal cutting was in this work also shown to be strongly affected by the elastic anisotropy of TiAlN, where the phase separation was aligned along the elastically softer <100> directions in the crystal. The presence of the anisotropic microstructure enhanced the mechanical properties compared to the isotropic case, mainly due to a shorter distance between the c-AlN and c-TiN domains in the anisotropic case. Further improvement of the metal cutting behavior was realized by depositing individual layers with an alternating bias. The individual bias layers exhibited microstructural differences with different residual stress states. The results of the metal cutting tests showed an enhanced wear resistance in terms of both crater and flank wear compared to coatings deposited with a fixed bias.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 75 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1583
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-106507 (URN)10.3384/diss.diva-106507 (DOI)978-91-7519-372-4 (ISBN)
Public defence
2014-06-11, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2014-05-09 Created: 2014-05-09 Last updated: 2014-05-09Bibliographically approved
2. High pressure and high temperature behavior of TiAlN
Open this publication in new window or tab >>High pressure and high temperature behavior of TiAlN
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This licentiate thesis mainly reports about the behavior of arc evaporated TiAlN at high pressures and high temperatures. The extreme conditions have been obtained in metal cutting, multi anvil presses or diamond anvil cells. Several characterization techniques have been used, including x-ray diffraction and transmission electron microscopy.

Results obtained during metal cutting show that the coatings are subjected to a peak normal stress in the GPa region and temperatures around 900 °C. The samples after metal cutting are shown to have a stronger tendency towards the favorable spinodal decomposition compared to heat treatments at comparable temperatures. We have also shown an increased anisotropy of the spinodally decomposed domains which scales with Al composition and results in different microstructure evolutions. Furthermore, multi anvil press and diamond anvil cell at even higher pressures and temperatures (up to 23 GPa and 2200 °C) also show that the unwanted transformation of cubic AlN into hexagonal AlN is suppressed with an increased pressure and/or temperature.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 46 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1540
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-78830 (URN)978-91-7519-863-7 (ISBN)
Presentation
2012-06-13, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 14:15
Opponent
Supervisors
Available from: 2012-06-21 Created: 2012-06-21 Last updated: 2014-09-18Bibliographically approved
3. Theoretical understanding of stability of alloys for hard-coating applications and design
Open this publication in new window or tab >>Theoretical understanding of stability of alloys for hard-coating applications and design
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The performance of modern hard coating materials puts high demands on properties such as hardness, thermal stability and oxidation resistance. These properties not only depend on the chemical composition, but also on the structure of the material on a nanoscale. This kind of nanostructuring will change during use and can be both beneficial and detrimental as materials grown under non-equilibrium conditions transforms under heat treatment or pressure into other structures with significantly different properties. This thesis aims to reveal the physics behind the processes of phase stability and transformations and how this can be utilized to improve on the properties of this class of alloys. This has been achieved through the application of various methods of first-principles calculations and analysis of the results on the basis of thermodynamics and electronic structure theory.

Within multicomponent transition metal aluminum nitride alloys (TMAlN) a number of studies have been carried out and presented here on ways of improving high temperature stability and hardness. Most (TMAl)N and TMN prefer a cubic B1 structure while AlN is stable in a hexagonal B4 phase, but for the purposes of hard coatings the metastable cubic B1 AlN phase, isostructural with the TMN phase is desired. It will be shown how the introduction of additional alloying components, such as Cr, into (TiAl)N changes the thermodynamic stability of phases so that new intermediary and metastable phases are formed during decomposition. In the case of such a (CrAl)N phase it is shown to have greater thermodynamic stability in the cubic phase than the pure AlN, resulting in improved high temperature hardness. Also, the importance of treating not just the binodal decomposition through the formation energy relative to end products but also the impact of spinodal decomposition from its second derivative due to the topology of formation energy surfaces is emphasized in the thesis. The impact of pressure on the AlN phase has also been studied through the calculation of a P-T diagram of AlN as part of a (TiAl)N alloy.

During the study of chemical alloying of TM components into AlN the alloying of low concentrations of these TM were treated in great detail. What is generally referred to as the AlN phase in decomposition is not entirely pure and can be expected to contain traces of any alloying components, such as Ti and Cr or whatever other metals may be present. Low concentration alloying of Cr, on the order of 5-10% is also shown to be stable with regard to isostructural decomposition. Detailed analysis of the effect of Ti and Cr impurities in AlN has been carried out along with a systematic search of AlN alloyed with small amounts of other TM components. The impact of these impurities on the electronic structure and thermodynamic properties is analyzed and the general trends will be explained through the occupation of impurity states by d-like electrons.

Theoretical treatment of such impurities is not straightforward however. AlN is an s-p semiconductor with a wide band gap while TM impurities generate states of a d-like nature situated inside the band gap. Such localized impurity states are expected to give rise to magnetic effects due to spin dependent exchange, in addition strong correlation effects might have to be taken into account. For that reason the use of hybrid functionals with orbital corrections according to the mHSE+Vw scheme, developed specifically for this class of materials, has been used and shown to influence the results during calculation of impurities of Ti and Cr.

In nanocomposite multilayered structures, composed of very thin layers of one material sandwiched between slabs of another, such as layers of SiN between TiN or ZrN, the material properties are greatly affected by the interfaces. In addition to the thermodynamic effects and lattice strains of the interfaces one also has to consider the atomic vibrational motion in the interface structure. Hence, dynamical stability of these thin multilayers is of great importance. As part of this thesis, results on the thermodynamic and dynamical stability of both TiN-SiN layers and ZrN-SiN will be presented. It will be shown that due to considerable dynamical instability in the interface structure of monolayered B1 SiN sandwiched between isostructural layers of B1 ZrN along (111) interfaces this structure cannot be expected to grow, instead preferring the stable (001) direction of growth.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 73 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1647
National Category
Physical Sciences Materials Engineering
Identifiers
urn:nbn:se:liu:diva-115405 (URN)10.3384/diss.diva-115405 (DOI)978-91-7519-112-6 (ISBN)
Public defence
2015-04-10, Planck, Fysikhuset, Campus Valla, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2015-03-16 Created: 2015-03-16 Last updated: 2015-03-16Bibliographically approved

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Norrby, NiklasLind, HansJohansson, M P.Tasnadi, FerencAbrikosov, IgorOdén, Magnus

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