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@PHDTHESIS{Norrby:170973,
author = {Norrby, Niklas},
title = {{M}icrostructural evolution of {T}i{A}l{N} hard coatingsat
elevated pressures and temperatures},
school = {Linköping University, Sweden},
type = {Dr.},
address = {Linköping},
publisher = {Linköping University - Tryck},
reportid = {DESY-2014-03100},
isbn = {978-91-7519-372-4},
series = {Linköping Studies in Science and Technology Dissertation
No. 1583},
year = {2014},
note = {Linköping University, Sweden, Diss., 2014},
abstract = {A typical hard coating on metal cutting inserts used in for
example turning,milling or drilling operations is TiAlN. At
elevated temperatures, TiAlNexhibits a well characterized
spinodal decomposition into coherent cubic TiNand AlN rich
domains, which is followed by a transformation from cubic
tohexagonal AlN. Using in-situ synchrotron x-ray radiation,
the kinetics of thesecond transformation was investigated in
this thesis and the strongtemperature dependence on the
transformation rate indicated a diffusionbased nucleation
and growth mechanism. The results gave additionalinformation
regarding activation energy of the transformation and the
criticalwavelength of the cubic domains at the onset of
hexagonal AlN. Afternucleation and growth, the hexagonal
domains showed a striking resemblancewith the preexisting
cubic AlN microstructure.During metal cutting, the tool
protecting coating is subjected totemperatures of ~900 ºC
and pressure levels in the GPa range. The results inthis
thesis have shown a twofold effect of the pressure on the
decompositionsteps. Firstly, the spinodal decomposition was
promoted by the appliedpressure during metal cutting which
was shown by comparisons with annealedsamples at similar
temperatures. Secondly, the detrimental transformationfrom
cubic to hexagonal AlN was shown to be suppressed at
elevatedhydrostatic pressures. A theoretical
pressure/temperature phase diagram,validated with
experimental results, also showed suppression of
hexagonalAlN by an increased temperature at elevated
pressures.The spinodal decomposition during annealing and
metal cutting was inthis work also shown to be strongly
affected by the elastic anisotropy ofTiAlN, where the phase
separation was aligned along the elastically softer<100>
directions in the crystal. The presence of the
anisotropicmicrostructure enhanced the mechanical properties
compared to the isotropiccase, mainly due to a shorter
distance between the c-AlN and c-TiN domainsin the
anisotropic case. Further improvement of the metal cutting
behaviorwas realized by depositing individual layers with an
alternating bias. Theindividual bias layers exhibited
microstructural differences with differentresidual stress
states. The results of the metal cutting tests showed
anenhanced wear resistance in terms of both crater and flank
wear compared tocoatings deposited with a fixed bias.},
keywords = {Dissertation (GND)},
cin = {DOOR},
cid = {I:(DE-H253)HAS-User-20120731},
pnm = {PETRA Beamline P07 (POF2-54G14)},
pid = {G:(DE-H253)POF2-P07-20130405},
experiment = {EXP:(DE-H253)P-P07-20150101},
typ = {PUB:(DE-HGF)11},
url = {https://bib-pubdb1.desy.de/record/170973},
}