Charpy Impact Properties of Hydrogen-Exposed 316L Stainless Steel at Ambient and Cryogenic Temperatures
metals
Article
Charpy Impact Properties of Hydrogen-Exposed 316L
Stainless Steel at Ambient and
Cryogenic Temperatures
Le Thanh Hung Nguyen , Jae-Sik Hwang , Myung-Sung Kim, Jeong-Hyeon Kim,
Seul-Kee Kim and Jae-Myung Lee *
Department of Naval Architecture and Ocean Engineering, Pusan National University, 30, Jangjeon-Dong,
Geumjeong-Gu, Busan 609-735, Korea; (L.T.H.N.); (J.S.H.);
(M.S.K.); (J.H.K.); (S.K.K.)
* Correspondence: ; Tel.: +82-51-510-2342
Received: 14 May 2019; Accepted: 27 May 2019; Published: 29 May 2019
Abstract: 316L stainless steel is a promising material candidate for a hydrogen containment system.
However, when in contact with hydrogen, the material could be degraded by hydrogen embrittlement
(HE). Moreover, the mechanism and the effect of HE on 316L stainless steel have not been clearly
studied. This study investigated the effect of hydrogen exposure on the impact toughness of 316L
stainless steel to understand the relation between hydrogen charging time and fracture toughness at
ambient and cryogenic temperatures. In this study, 316L stainless steel specimens were exposed to
hydrogen in different durations. Charpy V-notch (CVN) impact tests were conducted at ambient and
low temperatures to study the effect of HE on the impact properties and fracture toughness of 316L
stainless steel under the tested temperatures. Hydrogen analysis and scanning electron microscopy
(SEM) were conducted to find the effect of charging time on the hydrogen concentration and surface
morphology, respectively. The result indicated that exposure to hydrogen decreased the absorbed
energy and ductility of 316L stainless steel at all tested temperatures but not much difference was
found among the pre-charging times. Another academic insight is that low temperatures diminished
the absorbed energy by lowering the ductility of 316L stainless steel.
Keywords: cryogenic temperature; hydrogen embrittlement; impact load; charpy impact test
1. Introduction
The Marine Environment Protection Committee (MEPC) of the International Maritime
Organization (IMO) regulations met for its 72nd session with the aim to dramatically reduce the
greenhouse gas emissions from ships by at least 50% by 2050 compared to 2008 [1]. The new regulations
lead to the high demand for new eco-friendly fuels for marine ships and vessels with low greenhouse
gas emissions. Among the alternative energies, liquid hydrogen (LH2 ) has been of great concern
because it has zero carbon dioxide emissions in the exhaust gas and a higher energy-to-weight ratio in
comparison with conventional fuels, like natural gas or gasoline. Despite these advantages, hydrogen
can dissolve into materials and cause hydrogen embrittlement (HE) in hydrogen containers because of
its small size [2]. Furthermore, a low temperature of up to −253 ◦ C of liquid hydrogen could make the
materials used for LH2 vessels become brittle. Therefore, the effect of cryogenic temperature and HE
on the working capability of materials used for hydrogen containers must be understood. Figure 1
illustrates a hydrogen container.
Metals 2019, 9, 625; doi:10.3390/met9060625
www.mdpi.com/journal/metals
Metals 2019,
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9, x625
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Figure 1. Schematic diagram of a hydrogen container.
Figure 1. Schematic diagram of a hydrogen container.
For the transportation and storage of LH2 , 316L stainless steel is considered one of the most
For
transportation
and
of LH2, 316L stainless
steel because
is considered
one resistance
of the most
attractivethe
material
candidates
forstorage
liquid hydrogen-containing
vessels
of its high
to
attractive
material
candidates
for
liquid
hydrogen-containing
vessels
because
of
its
high
resistance
to
HE [3] and good mechanical properties at low temperatures [4]. Understanding the effect of cryogenic
HE
[3] and good
at low
temperatures
Understanding
the effect
of cryogenic
temperature
andmechanical
HE on the properties
performance
of 316L
stainless [4].
steel
is very important
in selecting
316L
temperature
and
HE
on
the
performance
of
316L
stainless
steel
is
very
important
in
selecting
316L
stainless steel as a material candidate for containing liquid hydrogen. However, the mechanism of
HE
stainless
steel as asteel
material
candidate
containing
liquid[5].
hydrogen. However, the mechanism of
on 316L stainless
has not
yet beenfor
clearly
understood
HE on
316L stainless
steel has notthe
yetinfluence
been clearly
understood
[5].
Former
studies investigated
of HE
on the mechanical
properties and microstructure
Former
studies
investigated
the
influence
of
HE
on
mechanical
properties
and
of 316L stainless steel. Fukuyama et al. (2004) conducted tensilethe
tests
at 10–70 MPa
of hydrogen
microstructure
of
316L
stainless
steel.
Fukuyama
et
al.
(2004)
conducted
tensile
tests
at
10–70
MPa
atmosphere and at ambient temperature for 316L stainless steel. They realized that the impact of
of
hydrogen
atmosphere
and
at
ambient
temperature
for
316L
stainless
steel.
They
realized
that
the
hydrogen on the tensile performance of the material was negligible. Hydrogen was only distributed
impact
of hydrogen
on and
the tensile
performance
ofnot
the uniform
material along
was negligible.
Hydrogenbecause
was only
in the thin
outer layer
its concentration
was
with the specimen
of
distributed
in
the
thin
outer
layer
and
its
concentration
was
not
uniform
along
with
the
specimen
its low diffusivity [6]. Kanezaki et al. (2008) cathodically charged 316L stainless steel in a H2 SO4
because
its=low
(2008)
cathodically
charged
steelinin
a
◦ C for 672eth.al.
solution of
(pH
3.5)diffusivity
at 27 A/m2[6].
, 50Kanezaki
They
found
that hydrogen
was316L
onlystainless
distributed
the
H
2SO4 solution (pH = 3.5) at 27 A/m2, 50 °C for 672 h. They found that hydrogen was only distributed
thin outer layer with a thickness of approximately 100–200 µm after cathodic charging and the high
in
the thinconcentration
outer layer with
thickness
of approximately
100–200
after
and the
hydrogen
wasa only
distributed
on the 100 µm
outer μm
layer
[7]. cathodic
The highcharging
nickel content
of
high
hydrogen
concentration
was
only
distributed
on
the
100
μm
outer
layer
[7].
The
high
nickel
316L stainless steel promotes a better stability of the austenite phase, which plays an important
role
content
of 316L
stainless
steel promotesfracture
a better
stability
of thelattice
austenite
phase, which
plays an
in resistance
against
hydrogen-assisted
[8].
In the cubic
of materials,
the presence
of
important
role
in
resistance
against
hydrogen-assisted
fracture
[8].
In
the
cubic
lattice
of
materials,
hydrogen in the matrix causes several changes, such as defects in transformation and phase formation.
the
ofstainless
hydrogensteels
in thelike
matrix
several
changes,
such
defects
transformationfrom
and
Forpresence
austenitic
316Lcauses
stainless
steel,
HE leads
toas
the
phaseintransformation
phase
formation.
For austenitic
steelsclose-packed)
lik (...truncated)
