Effect of water vapour content on thermal barrier coating lifetime

Abstract

Furnace cycle testing was conducted in air with 10, 50 and 90 vol.-% water vapour and compared to prior results in dry O 2 . The first series of experiments examined Pt diffusion and Pt modified aluminised bond coatings on second generation superalloy N5 at 1150uC with commercially vapour deposited yttria stabilised zirconia (YSZ) top coats. Compared to dry O 2 , the average lifetimes with Pt diffusion coatings were unaffected by the addition of water vapour, while the Pt modified aluminide coating average lifetime was reduced by .50% with 10% water vapour, but less reduction was observed with higher water contents. The second series of experiments examined MCrAlY and MCrAlYHfSi bond coatings and air plasma sprayed YSZ top coatings on superalloy X4 cycled at 1100uC. Compared to dry O 2 , the addition of 10% water vapour decreased the lifetime of MCrAlY by 28%. Higher average lifetimes were observed with Hf in the bond coating.

The Effect of High-Temperature Water Vapour on Degradation and Failure of Hot Section Components of Gas Turbine Engines

“…Under the 90% water vapour condition, there are γ' layers within the coating/substrate interface as well as at the gas interface. On these areas, the interdiffusion caused transformation results in a phase from high aluminum β-NiAl to the low aluminium γ' [36]. Rumpling that was found in the Pt-modified NiAl bond coat is caused the β-γ' transformation through interdiffusion.…”

“…The cross sections of a TBC-YSZ with Pt modified β-NiAl as bond coat were examined [36]. These sections are taken from samples after failure during the 1 h cycle test at 1150 • C. The bottom of the sections displays the specimen without the YSZ layer, while the top shows the opposite side with the bond coat beneath the YSZ layer.…”

Parsons Turbine Conference

“…Finally, Pint and Haynes11 examine the effect of water vapour content (10–90 vol.-) on the degradation in air of yttria stabilised zirconia (YSZ) thermal barrier coatings (TBCs) on ‘diffused-in’ platinum and aluminised platinum bond coats applied to N5 superalloy; also to that of YSZ on MCrAlY and MCrAlYHfSi thermally sprayed bond coats on X4. For ‘diffused-in’ Pt coatings lifetimes were unaffected by the addition of water vapour.…”