Phase stability, mechanical properties and thermal stability of Y alloyed Ti–Al–N coatings

Riedl, H.; Holec, David; Rachbauer, R.; Polcik, P.; Hollerweger, R.; Paulitsch, J.; Mayrhofer, P.H.

doi:10.1016/j.surfcoat.2013.07.030

Cited by 54 publications

(17 citation statements)

References 31 publications

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“…It has previously been shown that the early stage of the cubic to hexagonal transformation is typically induced in c-AlN-rich domains close to grain boundaries with high diffusivity [9]. However, despite the adverse effect that formation of h-AlN has on the material performance, previous studies have almost exclusively focused on understanding the spinodal decomposition and how it can be influenced by, for example, alloying [20][21][22][23][24][25], pressure [26,27], multilayers [28,29] and metal cutting [30]. Wüstefeld et al [31] used high-temperature glancing X-ray diffraction to study the effect of bias (-40, -80 and -120 V) on the spinodal decomposition and the c-AlN to h-AlN transformation at temperatures up to 850°C and an increase in bias was shown to increase the fraction of h-AlN in the annealed coating.…”

Section: Introductionmentioning

confidence: 99%

In situ X-ray scattering study of the cubic to hexagonal transformation of AlN in Ti1−xAlxN

et al. 2014

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In the present work, we have studied the decomposition of arc-evaporated Ti 0.55 Al 0.45 N and Ti 0.36 Al 0.64 N during heat treatments in vacuum by in situ synchrotron wide-angle X-ray scattering primarily to characterize the kinetics of the phase transformation of AlN from the cubic (c) NaCl structure to the hexagonal (h) wurtzite structure. In addition, in situ small-angle X-ray scattering measurements were conducted to explore details of the wavelength evolution of the spinodal decomposition, thus providing information about the critical size of the c-AlN-rich domains prior to the onset of the transformation to h-AlN. We report the fractional cubic to hexagonal transformation of AlN in Ti 1Àx Al x N as a function of time and extract activation energies between 320 and 350 kJ mol À1 depending on the alloy composition. The onset of the hexagonal transformation occurs $50 K lower in Ti 0.36 Al 0.64 N compared to Ti 0.55 Al 0.45 N where the high Al content alloy also has a significantly higher transformation rate. A critical wavelength for the cubic domains of $13 nm was observed for both alloys. Scanning transmission electron microscopy shows a c-TiN/h-AlN microstructure with a striking morphology resemblance to the c-TiN/c-AlN microstructure present prior to the hexagonal transformation.

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Section: Introductionmentioning

confidence: 99%

In situ X-ray scattering study of the cubic to hexagonal transformation of AlN in Ti1−xAlxN

et al. 2014

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“…Means to alter the thermal stability of Ti 1-x Al x N includes alloying with additional elements, e.g. Cr, Hf, Ta, Zr or Y [17][18][19][20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Improved metal cutting performance with bias-modulated textured Ti0.50Al0.50N multilayers

Norrby

Johansson-Jöesaar

Odén

2014

Surface and Coatings Technology

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“…Despite this shift, the pressure to completely stabilize the cubic structure of AlN is higher than the actual pressure acting on the coating during metal cutting. However, previous publications have shown an improved thermal stability, at ambient pressures, upon further alloying TiAlN with a forth element [82][83][84][85][86][87]. It is likely that this trend at an ambient pressure is valid at elevated pressures as well and thus a further shift of the equilibrium line is realized for quaternary coatings, i.e., closer to pressure levels during metal cutting.…”

Section: Pressure Dependence Of Quaternary Coatingsmentioning

confidence: 90%

“…The thermal stability of TiAlN, and how it is affected by, e.g., alloying with additional elements [82][83][84][85][86][87][88][89][90][91] or multilayer structures [8,57] is well studied in the literature. During a typical metal cutting operation however, large cutting forces (kN regime) prevail in combination with elevated temperatures.…”

Section: The Influence Of Pressurementioning

confidence: 99%

Microstructural evolution of TiAlN hard coatings at elevated pressures and temperatures

Norrby¹

2014

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LINKÖPING 2014The cover image shows nine two-dimensional x-ray diffractograms of TiAlN merged into one quarter circle. Going counterclockwise from an as-deposited sample, the parts show different stages of annealing. The color scheme is chosen to represent the motto "Stort hjärta, hårt arbete".Niklas Norrby, unless otherwise stated ISBN: 978-91-7519-372-4 ISSN: 0345-7524 Printed by LiU-Tryck, Linköping, Sweden, 2014 i Abstract 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 ii 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.iii Populärvetenskaplig sammanfattningI den här avhandlingen presenteras forskningsresultat på en keramisk beläggning, TiAlN (titanaluminiumnitrid), som ligger som ett skyddande skikt på svarvskär. Tjockleken på beläggni...

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Phase stability, mechanical properties and thermal stability of Y alloyed Ti–Al–N coatings

Cited by 54 publications

References 31 publications

In situ X-ray scattering study of the cubic to hexagonal transformation of AlN in Ti1−xAlxN

In situ X-ray scattering study of the cubic to hexagonal transformation of AlN in Ti1−xAlxN

Improved metal cutting performance with bias-modulated textured Ti0.50Al0.50N multilayers

Microstructural evolution of TiAlN hard coatings at elevated pressures and temperatures

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