IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
Rupture life,h
1000
Ti/C
4 5 6 7 8 9 10
973 K
100
0.16 0.20 0.24 0.28 0.32 0.36 0.40
Titanium, wt%
250 MPa
200 MPa
175 MPa
Fig.2 Influence of titanium on creep
rupture life of D9I SS (phosphorous =
0.025 wt%, silicon = 0.75 wt% and
carbon = 0.04 wt %).
Ti/C ratio is considered an
important parameter to assess
the influence of titanium. From
Fig. 2, it is seen that Ti/C ratio
of 5.5 to 6 provides maximum
creep strength in D9I SS
containing 0.025 wt%
phosphorous and 0.75 wt%
silicon. The variation of
minimum creep rate with
titanium content also showed a
minimum value corresponding
to 0.22 to 0.24 wt% titanium
(Fig. 3). Creep rupture ductility
generally decreased with
increase in titanium content.
Minimum creep rate, s-1
250 MPa
200 MPa
175 MPa
10 -8 973 K
10 -9
10 -10
0.20 0.25 0.30 0.35 0.40
Titanium, wt%
(b)
Fig.3 Influence of titanium on
minimum creep rate of D9I SS
(phosphorous = 0.025 wt%, silicon =
0.75 wt% and carbon = 0.04 wt %).
III.C.2. Effect of Titanium on the Void Swelling
Behavior in (15Ni-14Cr)-Ti Modified Austenitic Steels
Studied by Ion Beam Simulation - Step Height and
Positron Lifetime Studies
One of the important property
changes caused by irradiation
in the fast reactor structural
materials is void swelling. The
dimensional changes
introduced by void swelling
limits the lifetime of structural
components used in a reactor.
Therefore, resistance to void
swelling is a major
consideration in the choice of
materials for the core
components. The titanium
modified steels exhibit greatly
improved swelling resistance
under breeder reactor
conditions and consequently,
have become a prime
candidates for structural
applications. Titanium modified
(15Ni, 14Cr) steel and its
improved versions with
phosphorous additions
(designated as D9 and D9I) are
envisaged for use as fuel
cladding and wrapper materials
in Indian fast breeder reactor
(FBR) programme. Accelerated
heavy ions which have the
inherent advantage of
producing high displacement
rates have been used for
evaluating the effect of minor
alloying elements.
The void swelling behavior of
two steels: (A) (15Ni-14Cr)-
0.25Ti and (B) (15Ni-14Cr)-
0.15Ti were studied using
heavy ion irradiation for
understanding the influence of
titanium in the void swelling
resistance of the alloys .The
cold worked samples were preimplanted
with a uniform
helium concentration of 30
appm. This was followed by a 5
MeV nickel ion irradiation to
create a peak damage of ~
100 dpa at damage rate of 7
x10 -3 dpa/s at various
irradiation temperatures
between 700 and 970 K. The
gross swelling in the specimen
R&D FOR FBRs 45