U.S. patent application number 12/953520 was filed with the patent office on 2012-05-24 for metallic bondcoat or alloy with a high y/y' transition temperature and a component.
Invention is credited to Anand A. Kulkarni, Jonathan E. Shipper, Werner Stamm.
Application Number | 20120128525 12/953520 |
Document ID | / |
Family ID | 45218660 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120128525 |
Kind Code |
A1 |
Kulkarni; Anand A. ; et
al. |
May 24, 2012 |
Metallic Bondcoat or Alloy with a High y/y' Transition Temperature
and a Component
Abstract
A nickel-based coating or alloy is provided. The coating
includes tantalum preferably without rhenium. The coating or alloy
has stabilized the formation of phases .gamma./.gamma.' at high
temperatures leading to a reduction of local stresses. A component
is also provided. The substrate of the component includes a
nickel-based or cobalt-based superalloy.
Inventors: |
Kulkarni; Anand A.; (Oviedo,
FL) ; Shipper; Jonathan E.; (Orlando, FL) ;
Stamm; Werner; (Mulheim an der Ruhr, DE) |
Family ID: |
45218660 |
Appl. No.: |
12/953520 |
Filed: |
November 24, 2010 |
Current U.S.
Class: |
420/443 ;
420/441; 420/442; 420/455; 420/460 |
Current CPC
Class: |
Y02T 50/67 20130101;
Y02T 50/60 20130101; C23C 4/073 20160101; C22C 19/07 20130101; C22C
30/00 20130101; C22C 19/055 20130101; C22C 19/056 20130101; C22C
19/057 20130101 |
Class at
Publication: |
420/443 ;
420/441; 420/442; 420/455; 420/460 |
International
Class: |
C22C 19/05 20060101
C22C019/05; C22C 19/03 20060101 C22C019/03 |
Claims
1.-15. (canceled)
16. A nickel-based metallic coating or alloy, comprising: the
.gamma. and .gamma.' phases, wherein the coating or alloy comprises
tantalum in a range of between 4 wt % to 7.5 wt %.
17. The nickel-based coating or alloy according to claim 16,
wherein the tantalum is in the range of between 5 wt % and 6.8 wt
%.
18. The nickel-based coating or alloy according to claim 17,
wherein the tantalum is 6 wt %.
19. The nickel-based metallic coating or alloy according to claim
16, wherein the metallic coating or alloy contains no yttrium
and/or no platinum and/or no melting depressant.
20. The nickel-based metallic coating or alloy according to claim
16, wherein an amount of cobalt is in a range between 11 wt %-14.5
wt %.
21. The nickel-based metallic coating or alloy according to claim
20, wherein the amount of cobalt is in the range between 12 wt %-14
wt %.
22. The nickel-based metallic coating or alloy according to claim
21, wherein the amount of cobalt is 13 wt %.
23. The nickel-based metallic coating or alloy according to claim
16, wherein an amount of chromium is between 14 wt %-16 wt %.
24. The nickel-based metallic coating or alloy according to claim
16, wherein an amount of aluminum is between 9 wt %-13 wt %.
25. The nickel-based metallic coating or alloy according to claim
16, wherein an amount of yttrium is between 0.1 wt %-0.7 wt %.
26. The nickel-based metallic coating or alloy according to claim
16, wherein the metallic coating or alloy comprises no rhenium.
27. The nickel-based metallic coating or alloy according to claim
16, wherein the metallic coating or alloy comprises 0.1 wt % to 2
wt % rhenium.
28. The nickel-based metallic coating or alloy according to claim
16, wherein the coating or the alloy is a MCrAlY alloy with
M=nickel and/or M=cobalt.
29. The nickel-based metallic coating or alloy according to claim
16, wherein the coating or alloy includes a higher .gamma.'/.gamma.
transition compared to an NiCoCrAlY alloy or a coating with rhenium
and without tantalum.
30. The nickel-based metallic coating or alloy as claimed in claim
16, wherein the coating or alloy comprises no silicon, and/or no
hafnium, and/or no zirconium, and/or no tungsten.
31. The nickel-based metallic coating or alloy according to claim
16, wherein the coating or alloy comprises the .beta.-phase.
32. The nickel-based metallic coating or alloy as claimed in claim
16, wherein the coating or alloy consists of nickel, cobalt,
aluminum, chromium, and tantalum.
33. The nickel-based metallic coating or alloy as claimed in claim
32, wherein the coating or alloy further consists of yttrium.
34. The nickel-based metallic coating or alloy according to claim
16, wherein the coating or alloy comprises no iron.
35. A component, comprising: a nickel-based coating, comprising:
the .gamma. and .gamma.' phases, wherein the coating or the alloy
comprises tantalum in a range of between 4 wt % to 7.5 wt %
Description
FIELD OF INVENTION
[0001] The invention relates to a metallic bondcoat with phases of
.gamma. and .gamma.' a component.
BACKGROUND OF INVENTION
[0002] Components for the hot gas path in gas turbines are made
from Ni- or Co based materials. These materials are optimized for
strength and are not able to withstand oxidation and/or corrosion
attack at higher temperatures. Therefore, these kinds of materials
must be protected against oxidation by MCrAlY-coatings which can be
used as bondcoats for thermal barrier coating (TBC) systems as
well. In TBC systems, the MCrAlY coating is needed against hot gas
attack on one side and on the other side this coating is needed to
adhere the TBC to the substrate. Improving such systems against
oxidation will lead to increased bondcoats service temperatures
with increased life properties.
[0003] To protect the materials against hot corrosion/oxidation,
MCrAlY overlay coatings are coated mainly by low pressure plasma
spraying (LPPS), air plasma spraying (APS), electron beam physical
vapor deposition (EBPVD), cold spray (CS) or high velocity oxy-fuel
(HVOF) process. The MCrAlY coating is based on nickel and/or
cobalt, chromium, aluminum, silicon, rhenium and rare earth
elements like yttrium. With increasing bondcoat temperatures, these
coatings can fail which can lead to spallation of the thermal
barrier coating. Therefore, with increasing service temperatures,
improved coatings are needed to withstand the oxidation attack.
Additionally this kind of coatings should have acceptable
thermo-mechanical properties. These requests can only be achieved
by an optimized composition of the bond coat.
SUMMARY OF INVENTION
[0004] It is therefore the aim of the invention to solve the above
mentioned problem.
[0005] The problem is solved by a metallic coating or an alloy
according to the claims and a component according to the
claims.
[0006] In the dependent claims further amendments are disclosed
which can be arbitrarily combined with each other to yield further
advantages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] It shows
[0008] FIG. 1 a turbine blade,
[0009] FIG. 2 a gas turbine and
[0010] FIG. 3 a list of superalloys.
[0011] The figures and the description are only embodiments of the
invention.
DETAILED DESCRIPTION OF INVENTION
[0012] FIG. 1 shows a perspective view of a rotor blade 120 or
guide vane 130 of a turbomachine, which extends along a
longitudinal axis 121.
[0013] The turbomachine may be a gas turbine of an aircraft or of a
power plant for generating electricity, a steam turbine or a
compressor.
[0014] The blade or vane 120, 130 has, in succession along the
longitudinal axis 121, a securing region 400, an adjoining blade or
vane platform 403 and a main blade or vane part 406 as well as a
blade or vane tip 415.
[0015] As a guide vane 130, the vane 130 may have a further
platform (not shown) at its vane tip 415.
[0016] A blade or vane root 183, which is used to secure the rotor
blades 120, 130 to a shaft or disk (not shown), is formed in the
securing region 400.
[0017] The blade or vane root 183 is designed, for example, in
hammerhead form. Other configurations, such as a fir-tree or
dovetail root, are possible.
[0018] The blade or vane 120, 130 has a leading edge 409 and a
trailing edge 412 for a medium which flows past the main blade or
vane part 406.
[0019] In the case of conventional blades or vanes 120, 130, by way
of example solid metallic materials, in particular superalloys, are
used in all regions 400, 403, 406 of the blade or vane 120,
130.
[0020] Superalloys of this type are known, for example, from EP 1
204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO
00/44949.
[0021] The blade or vane 120, 130 may in this case be produced by a
casting process, also by means of directional solidification, by a
forging process, by a milling process or combinations thereof.
[0022] Workpieces with a single-crystal structure or structures are
used as components for machines which, in operation, are exposed to
high mechanical, thermal and/or chemical stresses.
[0023] Single-crystal workpieces of this type are produced, for
example, by directional solidification from the melt. This involves
casting processes in which the liquid metallic alloy solidifies to
form the single-crystal structure, i.e. the single-crystal
workpiece, or solidifies directionally.
[0024] In this case, dendritic crystals are oriented along the
direction of heat flow and form either a columnar crystalline grain
structure (i.e. grains which run over the entire length of the
workpiece and are referred to here, in accordance with the language
customarily used, as directionally solidified) or a single-crystal
structure, i.e. the entire workpiece consists of one single
crystal. In these processes, a transition to globular
(polycrystalline) solidification needs to be avoided, since
non-directional growth inevitably forms transverse and longitudinal
grain boundaries, which negate the favorable properties of the
directionally solidified or single-crystal component.
[0025] Where the text refers in general terms to directionally
solidified microstructures, this is to be understood as meaning
both single crystals, which do not have any grain boundaries or at
most have small-angle grain boundaries, and columnar crystal
structures, which do have grain boundaries running in the
longitudinal direction but do not have any transverse grain
boundaries. This second form of crystalline structures is also
described as directionally solidified microstructures
(directionally solidified structures).
[0026] Processes of this type are known from U.S. Pat. No.
6,024,792 and EP 0 892 090 A1.
[0027] The blades or vanes 120, 130 may likewise have coatings
protecting against corrosion or oxidation, e.g. MCrAlX (M is at
least one element selected from the group consisting of iron (Fe),
cobalt (Co), nickel (Ni), X is an active element and represents
yttrium (Y) and/or silicon and/or at least one rare earth element,
or hafnium (Hf)). Alloys of this type are known from EP 0 486 489
B1, EP 0 786 017 B1, EP 0 412 397 B1 or EP 1 306 454 A1.
[0028] The density is preferably 95% of the theoretical
density.
[0029] A protective aluminum oxide layer (TGO=thermally grown oxide
layer) forms on the MCrAlX layer (as an intermediate layer or an
outermost layer).
[0030] It is also possible for a thermal barrier coating,
consisting for example of ZrO.sub.2, Y.sub.2O.sub.3--ZrO.sub.2,
i.e. unstabilized, partially stabilized or fully stabilized by
yttrium oxide and/or calcium oxide and/or magnesium oxide and/or
one or more of rare earth element (lanthanum, gadolinium, yttrium,
etc.), which is preferably the outermost layer, to be present on
the MCrAlX.
[0031] The thermal barrier coating covers the entire MCrAlX layer.
Columnar grains are produced in the thermal barrier coating by
means of suitable coating processes, such as for example electron
beam physical vapor deposition (EB-PVD).
[0032] Other coating processes are conceivable, for example
atmospheric plasma spraying (APS), LPPS, VPS, solution precursor
plasma spray (SPPS) or CVD. The thermal barrier coating may include
porous grains which have microcracks or macrocracks for improving
its resistance to thermal shocks. The thermal barrier coating is
therefore preferably more porous than the MCrAlX layer.
[0033] The blade or vane 120, 130 may be hollow or solid in form.
If the blade or vane 120, 130 is to be cooled, it is hollow and may
also have film-cooling holes 418 (indicated by dashed lines).
[0034] FIG. 4 shows, by way of example, a partial longitudinal
section through a gas turbine 100.
[0035] In the interior, the gas turbine 100 has a rotor 103 which
is mounted such that it can rotate about an axis of rotation 102,
has a shaft 101 and is also referred to as the turbine rotor.
[0036] An intake housing 104, a compressor 105, a, for example,
toroidal combustion chamber 110, in particular an annular
combustion chamber, with a plurality of coaxially arranged burners
107, a turbine 108 and the exhaust-gas housing 109 follow one
another along the rotor 103.
[0037] The annular combustion chamber 110 is in communication with
a, for example, annular hot-gas passage 111, where, by way of
example, four successive turbine stages 112 form the turbine
108.
[0038] Each turbine stage 112 is formed, for example, from two
blade or vane rings. As seen in the direction of flow of a working
medium 113, in the hot-gas passage 111 a row of guide vanes 115 is
followed by a row 125 formed from rotor blades 120.
[0039] The guide vanes 130 are secured to an inner housing 138 of a
stator 143, whereas the rotor blades 120 of a row 125 are fitted to
the rotor 103 for example by means of a turbine disk 133.
[0040] A generator (not shown) is coupled to the rotor 103.
[0041] While the gas turbine 100 is operating, the compressor 105
sucks in air 135 through the intake housing 104 and compresses it.
The compressed air provided at the turbine-side end of the
compressor 105 is passed to the burners 107, where it is mixed with
a fuel. The mix is then burnt in the combustion chamber 110,
forming the working medium 113. From there, the working medium 113
flows along the hot-gas passage 111 past the guide vanes 130 and
the rotor blades 120. The working medium 113 is expanded at the
rotor blades 120, transferring its momentum, so that the rotor
blades 120 drive the rotor 103 and the latter in turn drives the
generator coupled to it.
[0042] While the gas turbine 100 is operating, the components which
are exposed to the hot working medium 113 are subject to thermal
stresses. The guide vanes 130 and rotor blades 120 of the first
turbine stage 112, as seen in the direction of flow of the working
medium 113, together with the heat shield bricks which line the
annular combustion chamber 110, are subject to the highest thermal
stresses.
[0043] To be able to withstand the temperatures which prevail
there, they can be cooled by means of a coolant.
[0044] Substrates of the components may likewise have a directional
structure, i.e. they are in single-crystal form (SX structure) or
have only longitudinally oriented grains (DS structure).
[0045] By way of example, iron-based, nickel-based or cobalt-based
superalloys are used as material for the components, in particular
for the turbine blade or vane 120, 130 and components of the
combustion chamber 110.
[0046] Superalloys of this type are known, for example, from EP 1
204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO
00/44949.
[0047] The guide vane 130 has a guide vane root (not shown here)
facing the inner housing 138 of the turbine 108 and a guide vane
head at the opposite end from the guide vane root. The guide vane
head faces the rotor 103 and is fixed to a securing ring 140 of the
stator 143.
[0048] A new modified coating was developed which fulfils the
requirements described above. This coating has a good long term
life, acceptable mechanical properties and improved oxidation
resistance. This is based on the presence of tantalum (Ta) in a
nickel based alloy but preferably without rhenium (Re). Tantalum
(Ta) stabilizes the formation of a three phase system
(.gamma.'/.gamma./.beta.) with a high .gamma.'/.gamma. transition
temperature. This will reduce the local stresses as well because
tantalum (Ta) will stabilize the high transition temperatures of
.gamma.' which is higher than the bondcoat service temperature of a
bond coat of this alloy.
[0049] Therefore there is preferably no need for hafnium (Hf) or
silicon (Si) or zirconium (Zr) or platinum (Pt) or any melting
depressant (like boron B) in the coating.
[0050] Very good results show the following elemental composition
for getting the proposed 3-phase-system with increased .gamma.'
transition temperatures: Ni-13Co-15.8Cr-11Al-6Ta.
[0051] A composition (Ni-25Co-17Cr-10Al-1.5Re--Y) which contains
rhenium (Re) instead of tantalum (Ta) has a lower .gamma.'/.gamma.
transition temperature because no tantalum is added.
[0052] The bondcoat is preferably a nickel (Ni) based super alloy
with addition of cobalt (Co), chromium (Cr), aluminum (Al) and
optionally yttrium (Y) which is preferably consisting of these
elements.
[0053] Very preferably it is a MCrAlY alloy, with M=Ni, Co.
[0054] Preferably the alloy contains no molybdenum (Mo), and/or no
tungsten (W) and/or columbium (Nb).
[0055] The substrate of the component comprises a nickel-based or
cobalt-based superalloy especially one of FIG. 3.
* * * * *