The Effect of APS-HVOF Bond Coating Thickness Ratio on TBC Furnace Cycle Lifetime

Combinations of NiCoCrAlY APS and high-velocity oxygen fuel (HVOF) bond coatings were deposited on alloy 247 disk substrates with yttria-stabilized zirconia (YSZ) top to assess the benefit air plasma sprayed (APS) ‘flash’ coatings. Using 1-h cycles at 1100 ℃ in 10% H2O HVOF-only APS-only as a baseline, it was found that flash extended average coating lifetime by 16% 35% thicker performing best. Principal component analysis energy dispersive spectroscopy (EDS) compositional mapping characterized after 0, 100, 300 500 failure showed Al depleted due both oxidation back diffusion into substrate. The had significant throughout so Al, diffused from substrate coating. Residual stress maps thermally-grown alumina scale obtained every 100 using photo-stimulated luminescence piezospectroscopy (PLPS) revealing Thick Flash slowest rate damage accumulation oxide scale.