8P14

機能性セラミックス被覆の流動リチウム鉛合金中
腐食挙動
Corrosion behavior of functional ceramic coatings inflowing lithium-lead alloy

近田 拓未1、赤星 江莉加1、芦田 真奈1、八木 重郎2、Schroer Carsten3、他
Takumi Chikada1, Erika Akahoshi1, Mana Ashida1, Juro Yagi2, Carsten Schroer3 et al.
1

静岡大、2京大、3カールスルーエ工科大
1
Shizuoka Univ., 2Kyoto Univ., 3KIT

1. Introduction
Ceramic coatings have been investigated as atritium permeation barrier and shown high permeation
reduction performance for the realization of an efficientfuel cycle and the lowest emission of radioactive
tritium into the environment from a fusion reactor. In
liquid blanket concepts, not only tritium permeation but
corrosion of the coatings by liquid tritium breeders
such as lithium-lead (Li-Pb) is an unavoidable concern.
Recently, the Li-Pb corrosion resistance of the singlelayer and multi-layer coatings was investigated in staticconditions [1,2]; however, a limited number of reports
investigating in flowing conditions are available.
Therefore, in this study, the Li-Pb exposure tests underrotating flow were conducted using the coatings withvarious layer structures to investigate the effect of layer
structure on the compatibility with flowing Li-Pb.
2. Experimental
Reduced activation ferritic/martensitic steel F82H
(Fe-8Cr-2W, F82H-BA07 heat) plates were used assubstrates. The coating procedure including formationof chromium oxide (Cr2O3) on the substrate, dipcoating of zirconium oxide (ZrO2) and erbium oxide(Er2O3) coating precursors, drying, pre-heat treatment,
and heat treatment is described in detail in Ref. [2]. The
layer structures of the coatings are presented in Fig. 1.
The heat treatment was performed every time afterdipping, drying, and pre-heating of each layer.
Li-Pb exposure tests under rotating flow wereperformed using a rotating apparatus at 550 ºC for 100‒
500 h with a rotating speed of 200 rpm. The samples
were fixed to the rotating blades by stainless steel wires.
The relative flow velocity on the samples is calculated
to be up to 0.06 m/s using a simplified computationalsimulation. Surface and cross-sectional observations of
the exposed samples were conducted by scanningelectron microscopy (SEM) with elemental analysis.

Fig. 1

Layer structure of coating samples.

3. Results and discussion
The change in the coating thickness after the Li-Pbexposure is summarized in Table 1. The thicknesses
increased by 40‒100 % after exposure for 100 h andthen decrease by approximately 10 % after 500 h.
Cross-sectional observation indicated that a corrosion
layer formed on the coating surfaces, leading to theincrease in the total thickness of the coatings. Cracks
were observed on the surfaces of Samples A and C after
exposure for 500 h. In Sample B, swelling of thecoating with a growth of iron oxide underneath thecoating was observed. Since a similar change inthickness was not confirmed in the static exposure tests
for up to 2000 h at 600 ºC [2], it was found that
corrosion was accelerated by flowing Li-Pb. The
results of Li-Pb exposure tests for up to 2000 h will be
included in the presentation.
Table 1 Li-Pb exposure time dependence of coating
thickness at 550 ºC under rotation flow
Sample A
Sample B
Sample C
Before300 nm90 nm
190 nm
100 h
470 nm
170 nm
340 nm
500 h
420 nm
N/A
300 nmReference[1] M. Matusnaga et al., J. Nucl. Mater. 511 (2018)534-543.
[2] E. Akahoshi et al., Fusion Eng. Des. 160 (2020)111874.