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High-Temperature Oxidation of Titanium Aluminium Nitride Coatings Visualized by Environmental Transmission Electron Microscopy

Makgae, Ofentse LU ; Lenrick, Filip LU orcid ; Bushlya, Volodymyr LU ; Andersson, Jon M. ; M'saoubi, Rachid LU and Ek, Martin LU orcid (2023) European Materials Research Society 2023 Spring Meeting
Abstract
Titanium-aluminium nitride (Ti1-xAlxN) coatings are used to achieve high oxidation and wear resilience in coated metal cutting tools. For the highest performance, the coatings' composition and microstructure are carefully controlled. However, it is difficult to obtain knowledge how these factors affect of the oxidation processes at the microstructural level because studies are most commonly performed: (1) post mortem and cannot observe the structural dynamics underlying the oxide formation in real-time; or (2) average over a large volume of the sample (and use powdered materials rather than actual coatings) and lack the spatial resolution to form connections to microstructure. Visualising the oxidation process at high spatial and temporal... (More)
Titanium-aluminium nitride (Ti1-xAlxN) coatings are used to achieve high oxidation and wear resilience in coated metal cutting tools. For the highest performance, the coatings' composition and microstructure are carefully controlled. However, it is difficult to obtain knowledge how these factors affect of the oxidation processes at the microstructural level because studies are most commonly performed: (1) post mortem and cannot observe the structural dynamics underlying the oxide formation in real-time; or (2) average over a large volume of the sample (and use powdered materials rather than actual coatings) and lack the spatial resolution to form connections to microstructure. Visualising the oxidation process at high spatial and temporal resolution, using technically relevant materials, would provide important insight into where oxidation initiates and how it proceeds to determine the performance of the coating.

Here, we directly visualise oxidation of Ti1-xAlxN (for x = 0, 0.18, 0.44, & 0.67) coatings from 100 to 1000 °C using environmental transmission electron microscopy (ETEM) imaging and energy dispersive X-ray spectroscopy (EDX). Samples are prepared from industrial coatings through focused ion beam milling, transferred to MEMS heating chips, and finally imaged in ETEM while heating in an O2 environment. The high-frame-rate ETEM movies show that oxidation in TiN proceeds at the grain boundaries and cracks formed during the heating process; in contrast, Ti1-xAlxN coatings transform from large as-deposited grains into oxide nanoparticles. Moreover, high-resolution ETEM imaging show the presence of anatase TiO2 at the early stages of oxidation across all compositions. Above ~850 °C, the oxide nanoparticles grow through crystal merging, diffusion and recrystallisation to form rutile TiO2. The EDX elemental maps coupled with secondary electron imaging reveal a uniform TiO2 sublayer decorated with increasing coverage of Al2O3 particles for x = 0.18 to 0.44. In contrast, coatings with x = 0.67 reveal a complete in-plane phase separation of Al- and Ti-oxides, which can rationalise their decreasing long-term oxidation resistance. Finally, the study provides insight into the real-time structural dynamics underpinning the oxidation resistance of Ti1-xAlxN coatings, illustrating how ETEM can uniquely complement other in situ techniques that have recently been applied to these materials.[1,2]

[1] Saringer C, Tkadletz M, Stark A, Schell N, Czettl C and Schalk N, Suf. Coatings Technol. 374 (2019) 617–24
[2] Chaar A B B, Rogström L, Johansson-Jöesaar M P, Barrirero J, Aboulfadl H, Schell N, Ostach D, Mücklich F and Odén M, J. Alloys Compd. 854 (2021) 157205 (Less)
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organization
publishing date
type
Contribution to conference
publication status
unpublished
subject
conference name
European Materials Research Society 2023 Spring Meeting
conference location
Strasbourg, France
conference dates
2023-05-29 - 2023-06-02
project
Skärverktyg under luppen – in situ studier av förstärkning och degradering och av ytbeläggningar på atomär nivå
language
English
LU publication?
yes
id
61d96e2e-bc92-40ff-b46e-759947da8a01
date added to LUP
2024-01-25 19:43:30
date last changed
2024-01-26 13:31:15
@misc{61d96e2e-bc92-40ff-b46e-759947da8a01,
  abstract     = {{Titanium-aluminium nitride (Ti1-xAlxN) coatings are used to achieve high oxidation and wear resilience in coated metal cutting tools. For the highest performance, the coatings' composition and microstructure are carefully controlled. However, it is difficult to obtain knowledge how these factors affect of the oxidation processes at the microstructural level because studies are most commonly performed: (1) post mortem and cannot observe the structural dynamics underlying the oxide formation in real-time; or (2) average over a large volume of the sample (and use powdered materials rather than actual coatings) and lack the spatial resolution to form connections to microstructure. Visualising the oxidation process at high spatial and temporal resolution, using technically relevant materials, would provide important insight into where oxidation initiates and how it proceeds to determine the performance of the coating.<br/><br/>Here, we directly visualise oxidation of Ti1-xAlxN (for x = 0, 0.18, 0.44, &amp; 0.67) coatings from 100 to 1000 °C using environmental transmission electron microscopy (ETEM) imaging and energy dispersive X-ray spectroscopy (EDX). Samples are prepared from industrial coatings through focused ion beam milling, transferred to MEMS heating chips, and finally imaged in ETEM while heating in an O2 environment. The high-frame-rate ETEM movies show that oxidation in TiN proceeds at the grain boundaries and cracks formed during the heating process; in contrast, Ti1-xAlxN coatings transform from large as-deposited grains into oxide nanoparticles. Moreover, high-resolution ETEM imaging show the presence of anatase TiO2 at the early stages of oxidation across all compositions. Above ~850 °C, the oxide nanoparticles grow through crystal merging, diffusion and recrystallisation to form rutile TiO2. The EDX elemental maps coupled with secondary electron imaging reveal a uniform TiO2 sublayer decorated with increasing coverage of Al2O3 particles for x = 0.18 to 0.44. In contrast, coatings with x = 0.67 reveal a complete in-plane phase separation of Al- and Ti-oxides, which can rationalise their decreasing long-term oxidation resistance. Finally, the study provides insight into the real-time structural dynamics underpinning the oxidation resistance of Ti1-xAlxN coatings, illustrating how ETEM can uniquely complement other in situ techniques that have recently been applied to these materials.[1,2]<br/><br/>[1] Saringer C, Tkadletz M, Stark A, Schell N, Czettl C and Schalk N, Suf. Coatings Technol. 374 (2019) 617–24<br/>[2] Chaar A B B, Rogström L, Johansson-Jöesaar M P, Barrirero J, Aboulfadl H, Schell N, Ostach D, Mücklich F and Odén M, J. Alloys Compd. 854 (2021) 157205}},
  author       = {{Makgae, Ofentse and Lenrick, Filip and Bushlya, Volodymyr and Andersson, Jon M. and M'saoubi, Rachid and Ek, Martin}},
  language     = {{eng}},
  month        = {{05}},
  title        = {{High-Temperature Oxidation of Titanium Aluminium Nitride Coatings Visualized by Environmental Transmission Electron Microscopy}},
  year         = {{2023}},
}