Oxidation Behavior of Hf-Modified Aluminide Coatings on Inconel-718 at 1050°C

摘要: Simple β-NiAl, Hf-modified Pt-diffused, Pt-modified β-(Ni,Pt)Al + ξ-PtAl 2 , and Hf-Pt-modified were cyclic oxidation tested at 1050°C in air on Inconel-718 substrates for up to 4370h. The Pt-diffused specimen failed most quickly, < 100 h, while the simple β-NiAl aluminide maintained a positive weight change ~1300 h. aluminides clearly improved behavior of both aluminides, sustaining zero only after 3600 4000 respectively. Hf additions did not immediately appear produce as strong an improvement expected, however, they more highly ranked when normalized by coating thickness. They also decreased surface rumpling, important TBC durability. Hf-rich NiAl grain boundaries, formed during processing, resulted HfO particles scales oxide pegs metal interface, all suggesting some level over-doping. high sulfur content substrate influenced spalling bare re-healing less protective Ni(Al,Cr) O 4 spinel-type (Ti,Cr,Nb)O rutile scales. evolution these features have been documented over 4370 h exposure. aluminum near failure was ~2-3 wt. %.