Factors Affecting TBC Furnace Cycle Lifetime: Temperature, Environment, Structure and Composition

Pint, Bruce A.; Haynes, J. Allen; Lance, Michael J.; Aldridge, H. L.; Viswanathan, Vaishak; Dwivedi, Gopal; Sampath, Sanjay

doi:10.1002/9781119075646.ch78

Cited by 4 publications

(2 citation statements)

References 37 publications

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“…After failure, samples were mounted in epoxy, polished and imaged using optical microscopy and scanning electron microscopy (SEM). the YHf and YHfSi bond coating lifetimes, and both were similar to the average lifetime previously obtained for HVOF YHfSi bond coatings [9]. Both VPS coatings also were evaluated at 1125°C but,while the average lifetimes were lower than at 1100°C, the effects of Si and temperature again were not statistically significant.…”

Section: Methodssupporting

confidence: 83%

“…Laboratory evaluations of TBCs typically begins with furnace cycle testing (FCT) where a cycle consists of heating acoated coupon in a furnace and holding for a period time (e.g., 1 or 100 h) at a fixed temperature without a temperature gradient across the coating followed by cooling to near room temperature. Our previous work has utilized FCT to study the effect of bond coating composition [4], roughness [5], superalloy composition [6], gas composition [4][5][6][7][8][9][10] and cycle frequency [8,9] on TBC lifetime.However, in some studies the FCT results were not statistically significant and, without a thermal gradient, FCT has limited value for evaluating multi-layer or low thermal conductivity top coatings.…”

Section: Introductionmentioning

confidence: 99%

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The effects of temperature and substrate curvature on TBC lifetime and residual stress in alumina scales beneath APS YSZ

Lance

Haynes

Pint

2016

Surface and Coatings Technology

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In order to assess the role of temperature on the lifetime of thermal barrier coatings (TBCs) and the development of residual stresses in Al 2 O 3 scales grown under yttria-stabilized zirconia (YSZ) top coatings, two vacuum plasma sprayed (VPS) NiCoCrAlYHf bond coating (BC) compositions, with and without Si, were deposited on Hf-rich directionally-solidified (DS) 247 substrates and then coated with air plasma sprayed (APS) YSZ. Samples were thermally-cycled at temperatures ranging from 1075 to 1150 °C with 1-h cycles in air with 10% H 2 O. Photostimulated luminescence spectroscopy (PSLS) was used to map residual stresses in the Al 2 O 3 scale at the YSZ/BC interface from the same region at regular cycling intervals. All samples exhibited similar stress distributions after 100 1-h cycles with the exception of the YHfSi BC cycled at 1150 °C which had a lower average compressive stress with more delaminations. This specimen also had the shortest TBC lifetime which shows that the PSLS measurements correlate well to interfacial damage accumulation in TBCs. The presence of Si had no effect on lifetime or residual stress but was found to reduce the amount of internal oxidation. The effect of sample curvature on the interfacial stress and TBC lifetime was also assessed by comparing TBC-coated rod specimens to flat buttons. Rod specimens failed much earlier than flat specimens and had lower Al 2 O 3 residual stress.

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Section: Methodssupporting

confidence: 83%