Decomposition pathways in nano-lamellar CVD Ti0.2Al0.8N
(2023) In Materialia 30.- Abstract
Recent progress in chemical vapour deposition (CVD) technology has enabled synthesis of metastable cubic Ti1−xAlxN coatings with x as high as 0.8–0.9. These coatings have unique micro- and nano-structures consisting of grains with epitaxially grown nanolamellae with different Al/Ti ratios, and exhibit exceptional hardness and resistance to wear and oxidation. Here, the thermal stability and decomposition of nano-lamellar CVD Ti0.2Al0.8N at temperatures between 800 and 1000 °C have been investigated using a combination of cross-sectional transmission X-ray nano-diffraction and scanning transmission electron microscopy. The decomposition started by formation of hexagonal AlN (h-AlN) in the grain... (More)
Recent progress in chemical vapour deposition (CVD) technology has enabled synthesis of metastable cubic Ti1−xAlxN coatings with x as high as 0.8–0.9. These coatings have unique micro- and nano-structures consisting of grains with epitaxially grown nanolamellae with different Al/Ti ratios, and exhibit exceptional hardness and resistance to wear and oxidation. Here, the thermal stability and decomposition of nano-lamellar CVD Ti0.2Al0.8N at temperatures between 800 and 1000 °C have been investigated using a combination of cross-sectional transmission X-ray nano-diffraction and scanning transmission electron microscopy. The decomposition started by formation of hexagonal AlN (h-AlN) in the grain boundaries throughout the coating. Below 900 °C, only limited further decomposition of the grain interiors occurred. At higher temperatures the formation of grain boundary h-AlN was followed by a bulk transformation of the nano-lamellar structure, starting at the top of the coating and subsequently sweeping inwards. The bulk transformation occurred initially through spinodal decomposition, followed by transformation of the Al-rich cubic phase to h-AlN, leading to a coarsened structure with Ti-rich domains in a h-AlN matrix. The behaviour is explained by the higher capability of grain boundaries and free surfaces to accommodate the volumetric expansion from the h-AlN formation. The results increase our understanding of the complicated decomposition processes in these metastable cubic coatings, which are of utmost importance from both technological and scientific perspectives.
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- author
- Bäcke, Olof ; Kalbfleisch, Sebastian LU ; Stiens, Dirk ; Manns, Thorsten ; Davydok, Anton ; Halvarsson, Mats and Hörnqvist Colliander, Magnus
- organization
- publishing date
- 2023
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- (Ti,Al)N, Chemical vapour deposition (CVD), Coatings, Phase separation, Phase stability
- in
- Materialia
- volume
- 30
- article number
- 101833
- publisher
- Elsevier
- external identifiers
-
- scopus:85165225055
- ISSN
- 2589-1529
- DOI
- 10.1016/j.mtla.2023.101833
- language
- English
- LU publication?
- yes
- id
- 05a8862c-0032-4784-a1f5-5134c1bf96e9
- date added to LUP
- 2023-09-04 15:20:01
- date last changed
- 2023-09-04 15:20:01
@article{05a8862c-0032-4784-a1f5-5134c1bf96e9,
abstract = {{<p>Recent progress in chemical vapour deposition (CVD) technology has enabled synthesis of metastable cubic Ti<sub>1−x</sub>Al<sub>x</sub>N coatings with x as high as 0.8–0.9. These coatings have unique micro- and nano-structures consisting of grains with epitaxially grown nanolamellae with different Al/Ti ratios, and exhibit exceptional hardness and resistance to wear and oxidation. Here, the thermal stability and decomposition of nano-lamellar CVD Ti<sub>0.2</sub>Al<sub>0.8</sub>N at temperatures between 800 and 1000 °C have been investigated using a combination of cross-sectional transmission X-ray nano-diffraction and scanning transmission electron microscopy. The decomposition started by formation of hexagonal AlN (h-AlN) in the grain boundaries throughout the coating. Below 900 °C, only limited further decomposition of the grain interiors occurred. At higher temperatures the formation of grain boundary h-AlN was followed by a bulk transformation of the nano-lamellar structure, starting at the top of the coating and subsequently sweeping inwards. The bulk transformation occurred initially through spinodal decomposition, followed by transformation of the Al-rich cubic phase to h-AlN, leading to a coarsened structure with Ti-rich domains in a h-AlN matrix. The behaviour is explained by the higher capability of grain boundaries and free surfaces to accommodate the volumetric expansion from the h-AlN formation. The results increase our understanding of the complicated decomposition processes in these metastable cubic coatings, which are of utmost importance from both technological and scientific perspectives.</p>}},
author = {{Bäcke, Olof and Kalbfleisch, Sebastian and Stiens, Dirk and Manns, Thorsten and Davydok, Anton and Halvarsson, Mats and Hörnqvist Colliander, Magnus}},
issn = {{2589-1529}},
keywords = {{(Ti,Al)N; Chemical vapour deposition (CVD); Coatings; Phase separation; Phase stability}},
language = {{eng}},
publisher = {{Elsevier}},
series = {{Materialia}},
title = {{Decomposition pathways in nano-lamellar CVD Ti<sub>0.2</sub>Al<sub>0.8</sub>N}},
url = {{http://dx.doi.org/10.1016/j.mtla.2023.101833}},
doi = {{10.1016/j.mtla.2023.101833}},
volume = {{30}},
year = {{2023}},
}