Abstract
The piezoelectric ultrasonic composite oscillator technique (PUCOT), operating near 80 kHz, was used to measure the temperature dependence, in the range 23–1000 °C, of dynamic Young's modulus,E, and internal friction,Q −1 in three compositions of low-pressure plasma-sprayed NiCrAlY: Ni-15.6Cr-5.2Al-0.20Y (16-5), Ni-17.2Cr-11.6Al-0.98Y (17−12), and Ni-33Cr-6.2 Al-0.95 Y (33−6). Ambient temperature (23 °C) dynamic Young's moduli for the three alloys were 205.0, 199.8, and 231.0 GPa, respectively. In each case, dE/dT was found to be — 0.06 GPa °C−1 over temperature ranges 23–800, 23–400 and 600–900, and 23–700 °C, respectively. Internal friction was essentially independent of temperature to about 600 °C (700 °C for the 16−5 alloy), at which point a temperature dependence of the formQ −1 =A exp (C/RT) was observed. The constantA for the three alloys was determined to be 62.7, 555, and 2.01 × 106, respectively. The constantC for the three alloys was determined to be 82.8, 111, and 170 kJ/mol−1, respectively. While the physical mechanism is not fully understood, both the pre-exponential constantA and the activation energyC correlate with durability in thermal barrier coatings (TBCs) wherein these alloys are used as bond coats.
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Cook, L.S., Wolfenden, A. & Brindley, W.J. Temperature dependence of dynamic Young's modulus and internal friction in LPPS NiCrAlY. J Mater Sci 29, 5104–5108 (1994). https://doi.org/10.1007/BF01151103
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DOI: https://doi.org/10.1007/BF01151103