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- Willmann, Herbert, et al.
(author)
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Hardness evolution of Al-Cr-N coatings under thermal load
- 2008
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In: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 23:11, s. 2880-2885
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Journal article (peer-reviewed)abstract
- Microstructure and hardness evolution of arc-evaporated single-phase Cubic Al0.56Cr0.44N and Al0.68Cr0.32N coatings have been investigated after thermal treatment in Ar atmosphere. Based on a combination of differential scanning calorimetry and x-ray diffraction studies, We Can Conclude that Al0.56Cr0.44N undergoes only small structural changes without any decomposition for annealing temperatures T-a <= 900 degrees C. Consequently, the hardness decreases only marginally from the as-deposited value of 30.0 +/- 1.1 GPa to 29.4 +/- 0.9 GPa with T-a increasing to 900 degrees C, respectively. The film with higher Al content (Al0.68Cr0.32N) exhibits formation of hexagonal (h) AlN at T-a >= 700 degrees C, which occurs preferably at grain boundaries as identified by analytical transmission electron microscopy. Hence, the hardness increases from the as-deposited value of 30.1 +/- 1.3 GPa to 31.6 +/- 1.4 GPa with T-a = 725 degrees C. At higher temperatures, where the size and volume fraction of the h-AlN phase increases, the hardness decreases to 27.5 +/- 1.0 GPa with T-a = 900 degrees C.
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