Note: Descriptions are shown in the official language in which they were submitted.
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~he present învention rela-tes to alloys suitable
for the manufacture of machine components subject to
mechanical-vibration, especially those components which
are subject to mechanical vibrations at high temperature,
such as gas turbine blades and other rotar~ components.
It is kno~n that, for the above-mentioned purposes,
use must be made of alloys having internal damping
properties, great strength, and good ductility at
temperatures which may reach 700 a or even higher sometimes
In particular this is the case when it is desired to
ensure a sufficiently long life for the first rows of
blades in turbines, which are subjected -to particularly
severe mechanical vibrations at high temperature.
In numerous applications 7 especially those in which
materials are subjected to mechanical vibrations, the
damping capacity of a material may be more important than
other properties such as the fatigue limi-t. The da~ping
capacity of a material is actually due -to four factors,
i.e. plastic deformation, the thermo-elastic ef~ect, the
magneto-elastic effect, and atomic diffusion~ ~he ma~neto-
electric effect is su-rely the most important in the casè
of alloys designed to be used in industry. It is well
recognized that ferromagnetic alloys have, for a number of
purposes, better properties than non-magnetic alloys. It
has been found that the high damping capacity of ferromagnetic
alloys is due to a magneto-mechanical hysteresis effect.
~he energ~ dissipated during a -tensile stress deformation
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cycle because o~ -the magneto-mech~ical ef~ect is
responsi-ble for the d~mping capacity of the material.
A material having a high damping capacity is thus a
magnetic material having as high as possible a C~rie
temperature, while a compromise must be found be-tween the
various properties required, i.e. strength at working
temperature, damping capacity, oxidation resistance, and
- duc-tility at ambient temperature.
In view of the above considerations, a number of
industrial materials such as, on the one hand, steels of -the
AISI 403 type (12~ Cr) and the AISI 422 type (12% Cr Mo W V~
type and, on the o-ther hand, cobalt-nickel alloys termed
NiVCo, and the 70% Mn 30% Cu alloy, have become generally
adopted, especially in the manufacture of turbine blades.
~ne choice of alloying elements capable of hardening the
! ferromagne-tic matrices is practically limited, because the
various additions have in general the effec-t of lowering
the aurie point of an alloy and -thus the damping capacity
of the ma-terial.
~or one reason or another, these alloys have dis-
advantages which limit the possibility of using them in
the above-mentioned applications. Among -these disadvantages
one should mention insu~flcient resistance to creep at high
temperature, manufacturing difficulties in assembly due to
hardness or to fragility or to indeformability, decrease in
damping capacity under high dynamic and static stresses, and
high cost.
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~he present inven-tion concerns an alloy particularly
suitable for -the above-mentiorled applications, and in
general for machine components which are subject, in use,
to more or less severe vibrations due to high speed of
rota-tion, to al-tern.a-ting movements, or to speed variations.
~his a]loy is characterized by a composition, by
weight, meeting the following relationships:
5% ~- ar ~ 25%
~ 5%
o G~ Mo ~ 5%
the ba.lance being Fe and its usual impurities~ Preferably,
the ~i content is at least 0.05 wt %.
It has been found that the above ma-terial simultaneously
exhibits good proper-ties of high-temperature strength,
ductility, creep resistance, and internal da;~ping, up to
temperatures of the order of 700C.
~he invention will be described further, by way of
example only, with reference to -the accompanying drawings,
in which:
~igure 1 is a graph o.E in.ternal damping verses
dynamic strain, at 0.5 Hz, for a component made of a
conventional alloy, at various static stresses,
~igure 2 is a graph similar to Fig.ure 1, for a
component according to the invention, at various sta-tic
stresses;
Figure 3 is a graph of internal damping, at 0.5 Hz,
versus ageing temperature, for a component according to
the invention subjected to di.fferent heat treatments;
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Figure 4 is a graph simila- to Figure 2, for R
component according to the invention, at various static
stresses; and
Figure 5 is a graph similar -to Figure 1, for
components made of various alloys.
~he various compositions of the alloys referred to
below and in the graphs are given in the following ~able,
together with the thermo-mechanical treatment (if any)
given to the alloy.
~ABLE
. _ . .. .. .
Alloy Fe Cr Ni Mo Ii ~iO2
------_______ /o /0 /0 / / 0/
________________________________________________~__________
AISI 410 balance - 13 -- - -- --
AI~I 316 ~ 16 13 1 -- __
B 3 E* " 13 ~~ 1.5 2-5 -
816** " 13 __ 1.5 3.5 -5
817** " 13 _- 1.5 3-5. 1.0
818** " 13 -- 1.5 3-5 1.5
819** " 13 -- 1.5 3-5 2.0
* extrusion at 1100C
~* extrusion at 1100C, reduction at 1050-1100 C from 19 to
10 mm reduction at 25C from 10 to 8~6 mm
heat treatment: 1 hour under argon at 1050 0
.. . .
By way of comparison, Figures 1 and 2 show, at 0.5Hz,
the in-ternal damping (in terms of the logarithmic decrement ~ )
as a function of the dynamic strain Y at various static
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stresses at roo~ temperature. ~igure 1 relates to the
conven-tional AISI ~10 steel whose co~posi-tion is se-t forth
in the above ~able, while ~igure 2 relates to an alloy
designated B3E whose composition is also given in -the ~able.
By heat treating the allo~ in question, it is
possible to modify the shape of tne dam~ing versus strain
curve by either varylng the maximum damping value of the
corresponding tension. By ageing and solution heat -treatment
it is possible to adjust the damping capacity of the allo~,
a~ illustrated in Fi~ure 3 ~fter various thermo-mechanical
treatments. Hardening of the metal matrix, no longer based
on the formation of carbides bu-t on precipitation of a
X (chi) phase of the Fe17 Cr17 (~i, Mo)5 type facilitates
the use of the alloy at a temperature of 700 a owing to
the stabili-ty of the precipitated phase. In ~igure 3,
internal damping at 0.5 Hz at a static stress ~ of 20 ~m 2
at room temperature is plotted against ageing temper~ture
for the alloy B3E extruded at 1100a ~d then soaked for
varl~us tlmes a-t the ageing temperature.
~urthermore, ~igure 4 illustrates the internal damping
capacity at 0.5 Hz as a function of the dynamic strain at
various levels of the static loads (M~m 2) applied, for the
alloy designated 817 in the above ~able, which: is a
dispersion-strengthened ferritic steel. ~his graph shows
particularly high damPing values under large dynamic stresses,
and small da~ping sensitivity with respect to the static
load applied, which cons-titutes a further advan-tage.
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Figure 5 shows how the values of in-ternal d~mping
vary as a function of the composition of the alloy, a-t a
single level (high le-vel) of static load ( ~) of 220 l'lNm 2
~his graph also indicates the damping curve corresponding
to the conventional aus-tenitic alloy AISI 31~A One can
no-te the large difference between this curve and the curves
corresponding to -the other allo-ys, among w~ich tha-t indicated
by 81~ is particularly interesting.
According to a variant of the invention and as
illustrated in Figures 4 and 5, it has been found -that it
is posslble to improve the properties of the alloy by
incorporation of a finely dispersed inert phase in the
matri~ and by taking advantage of the possibilities of
powder metallurgy. According to a preferred composition,
the addition of one or more of the following oxides -to the
metal matrix, ia -the indicated proportions, was found to
be particularly satisfac-tory:
~i2 ~ 4% by volume
Y203 ~ 4% by volume
Mg70 ~- 4% by volume
A1203 ~- 4% by volume.
