Decomposition pathways in nano-lamellar CVD Ti 0.2 Al 0.8 N
In: CVD - En ny generation av hårda beläggningar Materialia, Jg. 30 (2023)
Online
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Zugriff:
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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Decomposition pathways in nano-lamellar CVD Ti 0.2 Al 0.8 N
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Autor/in / Beteiligte Person: | Bäcke, Olof ; Kalbfleisch, Sebastian ; Stiens, Dirk ; Manns, Thorsten ; Davydok, Anton ; Halvarsson, Mats ; Hörnqvist Colliander, Magnus |
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Zeitschrift: | CVD - En ny generation av hårda beläggningar Materialia, Jg. 30 (2023) |
Veröffentlichung: | 2023 |
Medientyp: | unknown |
ISSN: | 2589-1529 (print) |
DOI: | 10.1016/j.mtla.2023.101833 |
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