Sea-salt-induced moderate-temperature degradation of thermally-sprayed MCrA1Y bond-coats

SURFACE & COATINGS TECHNOLOGY

卷:404

Article

Garces, Hector F.¹  Anh Tran¹  Sternlicht, Hadas¹  Miller, Michael²  Resnick, Michael²  Marino, Salvatore²  Choi, W. Brian²  Padture, Nitin P.¹ 

[1] Brown Univ, Sch Engn, Providence, RI 02912 USA

[2] ReliaCoat Technol LLC, East Setauket, NY 11733 USA

关键词: Hot corrosion;    Sea salt;    Oxidation;    Bond-coat;    Gas-turbine engines;    Thermal spray;   

DOI  :  10.1016/j.surfcoat.2020.126459

来源: Elsevier

【 摘 要 】

Metallic NiCoCrAlY bond-coats or overlay coatings are commonly used to protect superalloy components in the hot-section of shipboard gas-turbine engines. However, the accelerated degradation (or hot-corrosion) of such bond-coats at modest temperatures (similar to 850 degrees C) in the presence of impurities such as sea salt from the marine environment is a serious concern. Here, the interplay between the microstructure, presence/absence of sea salt or pure NaCl, heat-treatment duration, atmosphere and pre-oxidation, and the resulting degradation of thermally-sprayed NiCoCrAlY bond-coats is studied systematically. The degradation in the presence of sea salt or pure NaCl entails the formation of a two-layer oxide, where Cr-rich oxide is on top and Al-rich oxide is at the bottom. The mechanisms behind this two-layer oxide formation are investigated, which appear to be a combination of: (i) preferential formation of Al-rich oxide first, (ii) initial fluxing of the Al-rich TGO by the molten sea salt, and (iii) upward diffusion of Cr from the bond-coat through the Al-rich oxide layer. It is also shown that a modest pre-oxidation heat-treatment can be an effective way to mitigate sea-salt-induced degradation of NiCoCrAlY bond-coats.

【 授权许可】

Free