18Material Science and Technology of Japan, 54㸦2017㸧128㹼131Aug. 2017

Regular Paper
High Temperature Corrosion of ZrO2-4mol%Y2O3 Thermal Barrier
Coatings with Volcanic Ash
Byung-Koog JANG1,*, Seongwon KIM2, Yoon-Suk OH2 and Hyung-Tae KIM2
1

Research Center for Structural Materials, National Institute of Materials Science (NIMS), 1-2-1 Sengen,Tsukuba, 305-0047, Japan
2Korea Institute of Ceramic Engineering and Technology(KICET), 3321 Gyeongchung Rd, Sindun-Myeon,Icheon 17303, Korea
Received Jun. 15,2017; accepted for publication Jul. 6, 2017
Abstract
High temperature corrosion behavior was evaluated by chemical reaction between ZrO2-4mol%Y2O3 (YSZ) coatings  and volcanic ash at high temperature. YSZ coated specimens were obtained by electron-beam physical vapor
deposition (EB-PVD) process. The volcanic ash sprinkled YSZ coatings specimens were exposed at 1200°C for 10
min~50 hr by isothermal heat treatment. At the interface between YSZ coatings and volcanic ash, YSZ coatings werepartially dissolved in the molten volcanic glass, resulting in the degradation of YSZ coatings by the formation of thereacted region. The chemically reacted area between YSZ coatings and volcanic ash showed increasing tendency withan increase in isothermal heat treatment time.
Keywords: ZrO2-4mol%Y2O3, Thermal barrier coatings, EB-PVD, Volcanic ash

1.

Introduction
Thermal barrier coatings (TBCs) are applied to metallic

In spring 2010, the severe disruption in air travel and thecomponents of engines to prevent the temperature of the metal

economic loss approaching two billion dollars were caused bybecoming too high, as well as to provide environmental

the flight stop of all air plane due to explosive eruption ofprotection and extend the life of the components in the gas

Eyjafjallajökull volcano in Iceland because the volcanic ash

turbine engine. Among the various coating processes forclouds can give dangerous damage to aircraft jet engines during

producing TBCs, electron beam-physical vapor deposition

aircraft flying [7]. For the reason, the investigation of thermally(EB-PVD) is widely used because it has several advantages overchemical corrosion of TBCs is an important for long life time ofother techniques, including a high deposition rate, the ability toTBCs at high temperature.

use high melting point oxides, and excellent thermal shock Therefore, in this work, we investigate the influence ofresistance behavior due to the columnar microstructure of thevolcanic ash on high temperature corrosion of EB-PVD YSZcoatings produced [1–3]. The state-of-the art material for TBCs

coatings by isothermal heat treatment at a high temperature.

of turbine engine airfoils is tetragonal Y2O3 partially stabilizedZrO2.

Severalstudies

onthermalproperties

and2.

theExperimental Procedure

microstructure of TBCs fabricated by controlled deposition

The YSZ coatings onto coin-shaped dense ZrO2 substrates

processes have been reported [4-6].  However, TBCs have10.0 mm in diameter and 2 mm in thickness were performed byreceived the degradation or damage by chemical reaction with

the EB-PVD process under a vacuum level of 10-4 Pa using a 45

CMAS (calcium–magnesium–aluminum–silicates) or volcanic

kW electron beam gun and the use of YSZ ingot. The averageash particles attached to the TBCs surface at a high temperature,coated thickness was about 300 μm. The volcanic ash

above 1400°C, resulting in a critical accident for aircraft.  (Kagoshima, Japan) was used to evaluate the high temperature
corrosion of YSZ coatings. The volcanic ash of 1wt% against*Corresponding author: JANG.Byungkoog@nims.go.jp(128)