Role of Si segregation in the structural, mechanical, and compositional evolution of high-temperature oxidation resistant Cr-Si-B2±z thin films

Zauner L, Steiner A, Glechner T, Bahr A, Ott B, Hahn R, Wojcik T, Hunold O, Ramm J, Kolozsvári S, Polcik P, Felfer P, Riedl H (2023)

Publication Type: Journal article

Publication year: 2023

Journal

Journal of Alloys and Compounds Elsevier

Book Volume: 944

Article Number: 169203

DOI: 10.1016/j.jallcom.2023.169203

Abstract

This work investigates the influence of Si-alloying up to 17 at.% on the structural, mechanical, and oxidation properties of magnetron sputtered CrB2±z-based thin films. Density-functional theory calculations combined with atom probe tomography reveal the preferred Si occupation of Cr-lattice sites and an effective solubility limit between 3 to 4 at.% in AlB2-structured solid solutions. The addition of Si results in refinement of the columnar morphology, accompanied by enhanced segregation of excess Si along grain boundaries. The microstructural separation leads to a decrease in both film hardness and Young's modulus from H ∼ 24 to 17 GPa and E ∼ 300 to 240 GPa, respectively, dominated by the inferior mechanical properties of the intergranular Si-rich regions. Dynamic thermogravimetry up to 1400 °C reveals a significant increase in oxidation onset temperature from 600 to 1100 °C above a Si content of 8 at.%. In-situ X-ray diffraction correlates the protective mechanism with thermally activated precipitation of Si from the Cr-Si-B2±z solid solution at 600 °C, enabling the formation of a stable, nanometer-sized SiO2-based scale. Moreover, high-resolution TEM analysis exposes the scale architecture after dynamic oxidation to 1200 °C (10 K/min heating rate) – consisting only of ∼20 nm amorphous SiO2 beneath ∼200 nm of nanocrystalline Cr2O3. In summary, the study provides detailed guidelines connecting the chemical composition with the respective thin film properties of high-temperature oxidation resistant Cr-Si-B2±z coatings.

Authors with CRIS profile

Benedict Ott Professur für Atom Probe Tomography Peter Felfer Professur für Atom Probe Tomography

Involved external institutions

Technische Universität Wien / Vienna University of Technology AT Austria (AT) Oerlikon Balzers Coating Germany GmbH DE Germany (DE) Plansee Composite Materials GmbH DE Germany (DE)

How to cite

APA:

Zauner, L., Steiner, A., Glechner, T., Bahr, A., Ott, B., Hahn, R.,... Riedl, H. (2023). Role of Si segregation in the structural, mechanical, and compositional evolution of high-temperature oxidation resistant Cr-Si-B2±z thin films. Journal of Alloys and Compounds, 944. https://dx.doi.org/10.1016/j.jallcom.2023.169203

MLA:

Zauner, L., et al. "Role of Si segregation in the structural, mechanical, and compositional evolution of high-temperature oxidation resistant Cr-Si-B2±z thin films." Journal of Alloys and Compounds 944 (2023).

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