Effects of amorphous phase on hot corrosion behavior of plasma-sprayed LaMgAl 11 O 19 coating

S. Tsukada, S. Kuroda, M. Nishijima, H. Araki, Atsushi Yumoto, M. Watanabe

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Plasma-sprayed LaMgAl 11 O 19 (LaMA) coating as a novel thermal barrier coating candidate has been studied for more than a decade, but it tends to contain significant amounts of non-equilibrium amorphous phase due to rapid solidification. The microstructure of such as-sprayed LaMA coating was first studied in detail by a transmission electron microscope (TEM), which revealed that the coating consisted mostly of an amorphous phase but with very thin layers of crystalline (thickness ~ 100 nm) phase at the boundary of neighboring sprayed particles. A hot corrosion test was also conducted on an as-sprayed LaMA coating as well as on a fully-crystallized coating after heat treatment by a molten V 2 O 5 -Na 2 SO 4 mixture at 1100 °C. The coatings' cross sectional observation showed that the as-sprayed coating was affected over a wider area by the corrosion reaction than the crystallized coating. To clarify the intrinsic reactivity of the amorphous and crystalline LaMA phases with the molten salt, a piece of as-sprayed coating was crushed into powder, mixed with a salt, and tested at temperatures below and above the crystallization temperature. The reacted powder was analyzed by an X-ray diffractometer (XRD) to quantify the amounts of various phases in the sample as a function of time. The results revealed that the amorphous LaMA has a remarkably higher reaction rate with the molten salt than the crystalline phase. In fact, at the testing temperature of 1100 °C, corrosion of the sprayed LaMA powder proceeded much faster than crystallization, as almost 90% of LaMA was corroded within 30 min.

Original languageEnglish
Pages (from-to)95-105
Number of pages11
JournalSurface and Coatings Technology
Volume363
DOIs
Publication statusPublished - 2019 Apr 15

Fingerprint

hot corrosion
Corrosion
Plasmas
coatings
Coatings
Powders
Molten materials
Sprayed coatings
Salts
sprayed coatings
Crystallization
Crystalline materials
molten salts
corrosion
crystallization
Rapid solidification
Thermal barrier coatings
rapid solidification
Diffractometers
corrosion tests

Keywords

  • Hexaaluminate
  • High-resolution TEM
  • Molten salt
  • Quantitative XRD analysis
  • Thermal barrier coatings

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

Cite this

Effects of amorphous phase on hot corrosion behavior of plasma-sprayed LaMgAl 11 O 19 coating . / Tsukada, S.; Kuroda, S.; Nishijima, M.; Araki, H.; Yumoto, Atsushi; Watanabe, M.

In: Surface and Coatings Technology, Vol. 363, 15.04.2019, p. 95-105.

Research output: Contribution to journalArticle

Tsukada, S. ; Kuroda, S. ; Nishijima, M. ; Araki, H. ; Yumoto, Atsushi ; Watanabe, M. / Effects of amorphous phase on hot corrosion behavior of plasma-sprayed LaMgAl 11 O 19 coating In: Surface and Coatings Technology. 2019 ; Vol. 363. pp. 95-105.
@article{46052d5df86c42738e4095b84eaac7ee,
title = "Effects of amorphous phase on hot corrosion behavior of plasma-sprayed LaMgAl 11 O 19 coating",
abstract = "Plasma-sprayed LaMgAl 11 O 19 (LaMA) coating as a novel thermal barrier coating candidate has been studied for more than a decade, but it tends to contain significant amounts of non-equilibrium amorphous phase due to rapid solidification. The microstructure of such as-sprayed LaMA coating was first studied in detail by a transmission electron microscope (TEM), which revealed that the coating consisted mostly of an amorphous phase but with very thin layers of crystalline (thickness ~ 100 nm) phase at the boundary of neighboring sprayed particles. A hot corrosion test was also conducted on an as-sprayed LaMA coating as well as on a fully-crystallized coating after heat treatment by a molten V 2 O 5 -Na 2 SO 4 mixture at 1100 °C. The coatings' cross sectional observation showed that the as-sprayed coating was affected over a wider area by the corrosion reaction than the crystallized coating. To clarify the intrinsic reactivity of the amorphous and crystalline LaMA phases with the molten salt, a piece of as-sprayed coating was crushed into powder, mixed with a salt, and tested at temperatures below and above the crystallization temperature. The reacted powder was analyzed by an X-ray diffractometer (XRD) to quantify the amounts of various phases in the sample as a function of time. The results revealed that the amorphous LaMA has a remarkably higher reaction rate with the molten salt than the crystalline phase. In fact, at the testing temperature of 1100 °C, corrosion of the sprayed LaMA powder proceeded much faster than crystallization, as almost 90{\%} of LaMA was corroded within 30 min.",
keywords = "Hexaaluminate, High-resolution TEM, Molten salt, Quantitative XRD analysis, Thermal barrier coatings",
author = "S. Tsukada and S. Kuroda and M. Nishijima and H. Araki and Atsushi Yumoto and M. Watanabe",
year = "2019",
month = "4",
day = "15",
doi = "10.1016/j.surfcoat.2019.01.097",
language = "English",
volume = "363",
pages = "95--105",
journal = "Surface and Coatings Technology",
issn = "0257-8972",
publisher = "Elsevier",

}

TY - JOUR

T1 - Effects of amorphous phase on hot corrosion behavior of plasma-sprayed LaMgAl 11 O 19 coating

AU - Tsukada, S.

AU - Kuroda, S.

AU - Nishijima, M.

AU - Araki, H.

AU - Yumoto, Atsushi

AU - Watanabe, M.

PY - 2019/4/15

Y1 - 2019/4/15

N2 - Plasma-sprayed LaMgAl 11 O 19 (LaMA) coating as a novel thermal barrier coating candidate has been studied for more than a decade, but it tends to contain significant amounts of non-equilibrium amorphous phase due to rapid solidification. The microstructure of such as-sprayed LaMA coating was first studied in detail by a transmission electron microscope (TEM), which revealed that the coating consisted mostly of an amorphous phase but with very thin layers of crystalline (thickness ~ 100 nm) phase at the boundary of neighboring sprayed particles. A hot corrosion test was also conducted on an as-sprayed LaMA coating as well as on a fully-crystallized coating after heat treatment by a molten V 2 O 5 -Na 2 SO 4 mixture at 1100 °C. The coatings' cross sectional observation showed that the as-sprayed coating was affected over a wider area by the corrosion reaction than the crystallized coating. To clarify the intrinsic reactivity of the amorphous and crystalline LaMA phases with the molten salt, a piece of as-sprayed coating was crushed into powder, mixed with a salt, and tested at temperatures below and above the crystallization temperature. The reacted powder was analyzed by an X-ray diffractometer (XRD) to quantify the amounts of various phases in the sample as a function of time. The results revealed that the amorphous LaMA has a remarkably higher reaction rate with the molten salt than the crystalline phase. In fact, at the testing temperature of 1100 °C, corrosion of the sprayed LaMA powder proceeded much faster than crystallization, as almost 90% of LaMA was corroded within 30 min.

AB - Plasma-sprayed LaMgAl 11 O 19 (LaMA) coating as a novel thermal barrier coating candidate has been studied for more than a decade, but it tends to contain significant amounts of non-equilibrium amorphous phase due to rapid solidification. The microstructure of such as-sprayed LaMA coating was first studied in detail by a transmission electron microscope (TEM), which revealed that the coating consisted mostly of an amorphous phase but with very thin layers of crystalline (thickness ~ 100 nm) phase at the boundary of neighboring sprayed particles. A hot corrosion test was also conducted on an as-sprayed LaMA coating as well as on a fully-crystallized coating after heat treatment by a molten V 2 O 5 -Na 2 SO 4 mixture at 1100 °C. The coatings' cross sectional observation showed that the as-sprayed coating was affected over a wider area by the corrosion reaction than the crystallized coating. To clarify the intrinsic reactivity of the amorphous and crystalline LaMA phases with the molten salt, a piece of as-sprayed coating was crushed into powder, mixed with a salt, and tested at temperatures below and above the crystallization temperature. The reacted powder was analyzed by an X-ray diffractometer (XRD) to quantify the amounts of various phases in the sample as a function of time. The results revealed that the amorphous LaMA has a remarkably higher reaction rate with the molten salt than the crystalline phase. In fact, at the testing temperature of 1100 °C, corrosion of the sprayed LaMA powder proceeded much faster than crystallization, as almost 90% of LaMA was corroded within 30 min.

KW - Hexaaluminate

KW - High-resolution TEM

KW - Molten salt

KW - Quantitative XRD analysis

KW - Thermal barrier coatings

UR - http://www.scopus.com/inward/record.url?scp=85061838440&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85061838440&partnerID=8YFLogxK

U2 - 10.1016/j.surfcoat.2019.01.097

DO - 10.1016/j.surfcoat.2019.01.097

M3 - Article

AN - SCOPUS:85061838440

VL - 363

SP - 95

EP - 105

JO - Surface and Coatings Technology

JF - Surface and Coatings Technology

SN - 0257-8972

ER -