Thermal stability and oxidation behavior of quaternary TiZrAlN magnetron sputtered thin films: Influence of the pristine microstructure

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• 作者：G. Abadias ; I.A. Saladukhin ; V.V. Uglov ; S.V. Zlotski ; D. Eyidi
• 关键词：Quaternary transition metal nitrides ; TiZrAlN ; Hard coatings ; Annealing ; Oxidation resistance ; Phase decomposition
• 刊名：Surface and Coatings Technology
• 出版年：25 December, 2013
• 年：2013
• 卷：237
• 期：Complete
• 页码：187-195
• 全文大小：1540 K

文摘

Quaternary TiZrAlN coatings deposited by reactive magnetron sputtering from elemental targets have recently been shown to offer tailored nanostructural design with enhanced mechanical properties by fine-tuning the Al content at fixed N₂ partial pressure. Here, the influence of the microstructure of as-deposited (Ti,Zr)_{1 鈭?#xA0;x 鈭?#xA0;y}Al_xN_y coatings on their thermal stability and oxidation resistance is studied in details by scanning electron microscopy and X-ray diffraction. At low Al content (鈥榯ype I鈥?microstructure, 0 鈮?#xA0;x 鈮?#xA0;0.05), single-phase, stoichiometric (Ti,Zr,Al)N solid solutions with cubic structure are formed. These films are thermally stable after vacuum annealing at 600 掳C, the main structural changes being related to a defect annihilation and crystal recovery, leading to the development of a net tensile stress. Nanocomposite (Ti,Zr)_{1 鈭?#xA0;x 鈭?#xA0;y}Al_xN_y films with 鈥榯ype II鈥?microstructure (0.06 鈮?#xA0;x 鈮?#xA0;0.11; 0.34 鈮?#xA0;y 鈮?#xA0;0.39), consisting of cubic (Ti,Zr,Al)N nanocrystals embedded in an amorphous matrix, showed partial crystallization already at 600 掳C. At 950 掳C, phase decomposition takes place via the formation of cubic ZrN-rich and TiN-rich domains for both film-types. A decrease of the onset temperature for thermal decomposition is evidenced with increasing Al content. However, films with higher Al content delaminated after annealing at temperature higher than 800 掳C, suggesting that nitrogen deficiency is an important factor influencing the thermal stability. Oxidation experiments yield fully oxidized TiZrAlN coatings at 950 掳C, with the formation of a porous morphology and significant swelling (~ 200% increase in film thickness) and local blistering. Amorphous films with 鈥榯ype III鈥?microstructure (0.14 鈮?#xA0;x 鈮?#xA0;0.24; 0.24 鈮?#xA0;y 鈮?#xA0;0.31) show the best oxidation resistance, as the temperature for the formation of orthorhombic TiZrO₄ oxide layer is increased by ~ 150 掳C compared to Al-free coatings. However, films with higher Al content underwent extensive film flaking after air annealing.