U.S. patent number RE30,995 [Application Number 06/166,126] was granted by the patent office on 1982-07-13 for high integrity cocral(y) coated nickel-base superalloys.
This patent grant is currently assigned to General Electric Company. Invention is credited to John R. Rairden, III.
United States Patent |
RE30,995 |
Rairden, III |
July 13, 1982 |
**Please see images for:
( Certificate of Correction ) ** |
High integrity CoCrAl(Y) coated nickel-base superalloys
Abstract
A high temperature oxidation and corrosion resistant coated
nickel-base superalloy article comprising (a) a nickel-base
superalloy article, and .[.(b) a first.]. .Iadd.adjacent thereto
(b) a .Iaddend.CoCrAl(Y) coating .Iadd.having a substantially
uniform .Iaddend.composition .[.consisting essentially.].
.Iadd.composed .Iaddend.of, on a weight basis, approximately 26-32%
chromium, 3-9% aluminum, 0-1% yttrium, the rare earth elements,
platinum or rhodium, and the balance .[.nickel.]. .Iadd.cobalt and
impurities ordinarily associated with the aforementioned
constituents. .Iaddend.
Inventors: |
Rairden, III; John R.
(Schenectady, NY) |
Assignee: |
General Electric Company
(Schenectady, NY)
|
Family
ID: |
26861986 |
Appl.
No.: |
06/166,126 |
Filed: |
July 7, 1980 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
804936 |
Jun 9, 1977 |
04101715 |
Jul 18, 1978 |
|
|
Current U.S.
Class: |
428/680; 428/937;
428/938 |
Current CPC
Class: |
C23C
4/18 (20130101); C23C 14/16 (20130101); C23C
30/00 (20130101); C23C 28/023 (20130101); Y10T
428/12944 (20150115) |
Current International
Class: |
C23C
14/16 (20060101); C23C 30/00 (20060101); C23C
28/02 (20060101); C23C 4/18 (20060101); B32B
015/20 () |
Field of
Search: |
;428/652,668,678,680,937,938 ;75/171 ;427/34,405 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Wolf, P. C., "Vacuum Plasma Spray Process and Coatings", Trans. 9th
Int. Thermal Spraying Conf., pp. 187-196, (1980). .
Smith, R. W., et al., "Low Pressure Plasma Spray Coatings for Hot
Corrossion Resistance", Trans. 9th Int. Thermal Spraying Conf., pp.
334-343, (1980). .
Powell, C. F., et al., Vapor Deposition, John Wiley & Sons,
Inc., pp. 242-246, (1966). .
Kennedy, K., "Alloy Deposition from Single and Multiple Electron
Beam Evaporation Sources", AVS 1968 Regional Symposia, pp. 1-8.
.
Messbacher, A., et al., "Vacuum Plasma Spraying of Protective Hot
Gas Corrossion Coatings", Trans. 8th Int. Thermal Spray Conf. Amer.
Weld Soc., pp. 25-37, (1976). .
Rairden, J. R., et al., "The 3rd Conference on Gas Turbine
Materials in a Marine Environment Coatings for Directional
Eutectics", pp. 1-11, (9/76). .
Rairden, J. R., et al., "Coatings for Protecting Nickel-Base TaC
Eutectics Against Oxidation", Thin Solid Films, vol. 40, pp.
291-298, (1977). .
Boone, D. H., et al., "Electron Beam Evaporation . . . ", Thin
Solid Films, vol. 64, pp. 299-304, (1979). .
Talboom, F. P., et al., Evaluation of Advanced Superalloy
Protection Systems, NASA CR-72813 PWA-4055, pp. 1-9, 24, 46-56,
(1970). .
Foster, J. S., et al., "Vacuum Deposition of Alloys-Theoretical and
Practical Considerations", J. Vac. Sci., vol. 9, pp. 1379-1381,
1384, (1972). .
Nimmagadda, R., et al., "Preparation of Alloy by Continuous
Electron Beam Evaporation from a Single Rod-Fed Source", J. Vac.
Sci. Tech., vol. 9, (1972). .
Boone, D. H., et al., "Some Effects of Structure . . . ", J. Vac.
Sci. Technol., vol. 11, pp. 641-646, (1974). .
Rairden, J. R., et al., Coatings for Directional Eutectics, The 3rd
Conf. on Gas Turbines in a Marine Environment Paper 4, pp. 1-11,
(9/76). .
Rairden, J. R., et al., Coatings for Directional Eutectics, NASA
CR-135050, NAS 3-17815, pp. 1-73 and D-1 to ll, (7/25/76). .
Jackson, M. R., et al., Coatings for Directional Eutectics, NASA
SRD-74-047, NASA CR-134665, pp. 1-87, D1-12, (1/74)..
|
Primary Examiner: Lewis; Michael L.
Attorney, Agent or Firm: MaLossi; Leo I. Davis, Jr.; James
C.
Claims
I claim:
1. A high temperature oxidation and corrosion resistant coated
nickel-base superalloy article .[.having a thermal expansion
coefficient value in inches per inch per .degree.F. measured over a
temperature range of
(i) 100.degree.-1200.degree. F. of from 8.45 to 9.05, and
(ii) 100.degree.-1740.degree. F. of from 9.45 to 10.05;.].
.Iadd.characterized by high coating-substrate interface integrity,
said article .Iaddend.comprising:
(a) a nickel-base superalloy, and
(b) a .[.first.]. CoCrAl(Y) coating .Iadd.providing the outer
surface of said article, said coating having a substantially
uniform .Iaddend.composition .[.consisting essentially.].
.Iadd.composed .Iaddend.of, on a weight basis, approximately 26-32
percent chromium, 3-9 percent aluminum, and 0-1 percent yttrium,
other rare earth elements, platinum or rhodium, and the balance
cobalt .Iadd.and impurities ordinarily associated with the
aforementioned constituents.Iaddend..[...]..Iadd., said nickel-base
superalloy and said CoCrAl(Y) coating having substantially matching
thermal expansion coefficient values with the maximum difference
between the thermal expansion coefficient value of said substrate
and the thermal expansion coefficient value of said coating being
about 4 percent over a temperature range from 100.degree. F. to
1740.degree. F. .Iaddend.
2. A claim 1 article, wherein
.[.(a) said nickel-base superalloy consists essentially of, on a
weight basis,.].
.[.(b) said first.]. .Iadd.the .Iaddend.coating contains 29%
chromium, 6% aluminum, 1% yttrium and the balance cobalt. .[.3. A
claim 2 article, further comprising
(c) an overcoating of aluminum..]. .[.4. A claim 3 article,
wherein
(b) said first coating has a thickness of about 1-20 mils,
(c) said second coating penetrates the first coating to a depth no
nearer than 1/2 mil measured from the interface of the nickel-base
superalloy and first coating..]. .[.5. A claim 4 article,
wherein
(b) said first coating is deposited by physical vapor deposition
and the coating thickness is about 1-5 mils,
(c) said second coating is deposited by chemical vapor
deposition..]. .[.6. The claim 4 article, wherein
(b) said first coating is deposited by plasma spraying and has a
coating thickness of 3-10 mils..].
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a high temperature oxidation and
corrosion resistant coated nickel-base superalloy article
comprising (a) a nickel-base superalloy article, and .[.(b) a
first.]. .Iadd.adjacent thereto (b) a .Iaddend.CoCrAl(Y) coating
.Iadd.having a substantially uniform .Iaddend.composition
.[.consisting essentially.]. .Iadd.composed .Iaddend.of, on a
weight basis, approximately 26-32% chromium, 3-9% aluminum, 0-1%
yttrium, the rare earth elements, platinum or rhodium, and the
balance .[.nickel.]. .Iadd.cobalt and impurities ordinarily
associated with the aforementioned constituents.Iaddend.. An
aluminide overcoating can be applied to the CoCrAl(Y) coated
superalloys and constitute another embodiment of my invention.
2. Description of the Prior Art
Evans et al. in U.S. Pat. No. 3,676,085 describe coated nickel-base
superalloys wherein the coating composition consists essentially
of, on a weight basis, 15-40% chromium, 10-25% aluminum, 0.01-5%
yttrium or the rare earth elements and the balance cobalt. Evans et
al. .[.teache.]. .Iadd.teach .Iaddend.that when the aluminum
content of the CoCrAl(Y) coating is below about 10% there is
insufficient aluminum present in the coating system to provide the
desired long term durability in the coating.
Unexpectedly, I have found that nickel-base superalloys when coated
with CoCrAl(Y) coatings having an aluminum content of less than 10%
have outstanding physical and chemical properties, i.e. significant
oxidation and corrosion resistance and high coating-substrate
interface integrity. These outstanding properties are not
associated with nickel-base superalloys when coated with the
coating systems described by Evans et al. referenced above.
DESCRIPTION OF THE INVENTION
This invention embodies a high temperature oxidation and corrosion
resistant coated nickel-base superalloy article comprising (a) a
nickel-base superalloy article of manufacture, and .[.(b) a
first.]. .Iadd.adjacent thereto (b) a .Iaddend.CoCrAl(Y) coating
.Iadd.having a substantially uniform .Iaddend.composition
.[.consisting essentially.]. .Iadd.composed .Iaddend.of, on a
weight basis, approximately 26-32% chromium, 3-9% aluminum, and
0-1% yttrium, the rare earth elements, platinum or rhodium, and the
balance .[.nickel.]. .Iadd.cobalt and impurities ordinarily
associated with the aforementioned constituents.Iaddend..
My invention is more clearly understood from the following
description taken in conjunction with the accompanying drawings,
where:
FIG. 1 is a photomicrograph (500X) of a CoCrAl(Y) coated
nickel-base IN-738 superalloy having a coating composition of Evans
et al. U.S. Pat. No. 3,676,085, i.e. Co-22Cr-13Al-1Y. This figure
illustrates the low integrity of a CoCrAl(Y) coated nickel-base
superalloy of the prior art, i.e. a coating which has a significant
and a substantial tendency to separate from a superalloy substrate
thereby failing to give the oxidation and corrosion resistant
coating integrity desired for nickel-base superalloys.
FIG. 2 is a photomicrograph (500X) of a CoCrAl(Y) coated
nickel-base IN-738 superalloy having a coating composition of my
invention, i.e. Co-29Cr-6Al-1Y.
This figure illustrates the high integrity of a CoCrAl(Y) coated
nickel-base superalloy of my invention, i.e. a coating .Iadd.of
substantially uniform composition .Iaddend.which does not have a
significant or substantial tendency to separate from a superalloy
substrate thereby giving the oxidation and corrosion resistance
coating integrity desired for nickel-base superalloys. The coated
nickel-base superalloys of my invention have a thermal expansion
coefficient value .alpha. as measured in inches .Iadd.10.sup.-6
.Iaddend.per inch per .degree.F. (in./in./.degree.F.) over a
temperature range of (i) 100.degree.-1200.degree. F. of 8.45 to
9.05 in./in./.degree.F. and (ii) 100.degree. to 1740.degree. F. of
9.45 to .Badd..[.10.5.]..Baddend. .Iadd.10.05
.Iaddend.in./in./.degree.F.
A presently preferred nickel-base superalloy employed in my
invention "IN-738" is of the following general composition:
______________________________________ Ingredient IN-738
______________________________________ C 0.17 Mn 0.10 Si 0.30 Cr
16.0 Ni Bal. Co 8.5 Mo 1.75 W 2.6 Cb 0.9 Ti 3.4 Al 3.4 B 0.01 Zr
0.10 Fe 0.50 Other 1.75 Ta
______________________________________
This superalloy has a thermal expansion coefficient value .alpha.
measured in .Iadd.10.sup.-6 .Iaddend. in./in./.degree.F. over the
temperature ranges set out above of 8.7.+-.0.1 and 9.7.+-.0.1,
respectively.
A presently preferred CoCrAl(Y) coating employed in my invention
"GT-29" is of the following general composition: Co-29Cr-6Al-1Y.
This coating has a thermal expansion coefficient .alpha. measured
in .Iadd.10.sup.-6 .Iaddend. in./in./.degree.F. over the
temperature ranges set out above of 8.8.+-.0.1 and 9.9.+-.0.1,
respectively.
.Iadd.As is established hereinbelow, a successful substrate/coating
combination within the teachings of this invention employs IN-738
as the nickel-base superalloy and Co-29Cr-6Al-1Y as the coating
composition. The approximate percent difference in coefficients of
thermal expansion successfully tolerated in the tests described are
calculated from the data set forth above as follows:
__________________________________________________________________________
TEC* MAX. TEC % IN-738 Co-29Cr-6Al-1Y DIFFERENCE DIFFERENCE
__________________________________________________________________________
8.7 .+-. 0.1 8.8 .+-. 0.1 8.9 - 8.6 = 0.3 ##STR1## 9.7 .+-. 0.1 9.9
.+-. 0.1 10.0 - 9.6 = 0.4 ##STR2##
__________________________________________________________________________
*Thermal Expansion Coefficient 10.sup.-6 in./in./.degree.F.
Thus, in sum, this set of calculations shows that the combination
of these materials had a maximum TEC difference of about 4 percent.
.Iaddend.
The nickel-base superalloys and CoCrAl(Y) alloys employed in my
invention can be prepared by any method well-known to those
skilled.
The CoCrAl(Y) coatings can be applied to the nickel-base
superalloys by means, such as physical or chemical vapor
deposition, or any other means well-known to those skilled in the
art for the application of CoCrAl(Y) coatings to superalloys. Among
the coating techniques that can be used are those described in
Flame Spray Handbook, Volume III, by H. S. Ingham and A. P.
Shepard, published by Metco, Inc., Westbury, Long Island, New York
(1965),
Vapor Deposition, edited by C. F. Powell, J. H. Oxley and J. M.
Blocher, Jr., published by John Wiley & Sons, Inc., New York
(1966), etc.
In general, the CoCrAl(Y) coated nickel-base superalloys can have
any coating thickness sufficient to give a desired oxidation and
corrosion resistance. Generally economic and effective coating
thicknesses are 1-20 mils for most commercial applications. In
preferred embodiments, where electron-beam techniques are employed
the coating thicknesses range from 1-5 mils and where plasma flame
spray techniques are employed the coating thicknesses range from
3-10 mils. In another preferred embodiment where an aluminide
overcoating is employed, the aluminide overcoating--including any
duplex heat treatment where the aluminide overcoating is heated for
periods of time from 30 or 60 to 120 minutes at elevated
temperatures of 850.degree. to 1200.degree. F. in air, argon, etc.,
for the purpose of diffusing aluminum into the CoCrAl(Y)
coating--the .[.aluminuide.]. .Iadd.aluminide .Iaddend.process is
carried out in a manner which limits the aluminum penetration into
the CoCrAl(Y) coating to a distance no nearer than a 1/2 mil
measured from the interface of the nickel-base superalloy and the
CoCrAl(Y) coating. This aluminide diffusion penetration limitation
is essential to the integrity of the CoCrAl(Y) nickel-base
superalloy interface since as indicated hereinbefore (as
illustrated by FIG. 1) an increase in the aluminum content of the
CoCrAl(Y) coating to levels of 10% or more deleterious affects the
integrity of the coating composition.
My invention is further illustrated by the following examples:
EXAMPLE I
An experimental series was designed to study the expansion match
characteristics of nickel-base superalloys and CoCrAl(Y)
compositions as well as their oxidative and corrosion
resistance.
Test specimen pins of IN-738 were prepared which had been lightly
abraded with a No. 3 alumina powder. The resulting pins were 4.4
centimeters long and 0.25 cm. in diameter. A series of CoCrAl(Y)
ingots having the compositions set out hereafter in Table I were
electron-beam deposited on the abraded IN-738 pin substrates at a
deposition rate of approximately 0.1 mils per minute while the pins
were rotated at approximately 10 revolutions per minute. The
coatings were deposited at various pins substrate temperatures,
e.g. 1022.degree. F., 1292.degree. F., 1562.degree. F. and
1832.degree. F. The CoCrAl(Y) coated pins were thermal cycled
during deposition over a temperature range of from approximately
1832.degree. F. to 70.degree. F. (room temperature).
.[.Mellographic.]. .Iadd.Metallographic .Iaddend.examination via
photomicrographs--illustrated by FIGS. 1 and 2--shows that the
CoCrAl(Y) compositions of Evans et al. are not suited to
nickel-base superalloys defined herein since high aluminum
CoCrAl(Y) coatings as deposited on the nickel-base superalloy
IN-738 separate from the substrate during thermal cycling over a
temperature range of from 1832.degree.-70.degree. F.
TABLE I ______________________________________ Associated Photo-
Inventors Compositions micrographs
______________________________________ Evans et al., Prior Art
Co-18Cr-17Al-1Y -- Compositions Co-22Cr-13Al-1Y FIG. 1
Co-26Cr-9Al-1Y -- Rairden's, This Co-29Cr-6Al-1Y FIG. 2 Invention's
Compositions (RD-7240) Co-30Cr-9Al-1Y -- Co-32Cr-3Al-1Y
______________________________________
EXAMPLE II
Another series of CoCrAl(Y) coated IN-738 pin samples were prepared
as described in Example I above--having the coating compositions
set out hereafter in Table II--were subjected to a burner rig test
which simulated conditions used in a marine gas turbine engine
under highly corrosive conditions. The test was run to coating
failure using a diesel fuel containing 1% by weight of sulfur and
467 parts per million sea salt at a temperature 1600.degree. F.
coupled with thermocycling to room temperature 3 to 5 times per
week. The CoCrAl(Y) coated IN-738 samples were evaluated and
characterized according to hours to failure, failure being defined
as a condition wherein the results of the burner rig corrosion test
conditions set out in Table II hereafter:
TABLE II ______________________________________ Inventors
Compositions Hours to Failure*
______________________________________ Evans et al. Co-22Cr-13Al-1Y
605 Rairden's Co-32Cr-3Al-1Y 1235 Co-29Cr-6Al-1Y 1675
Co-30Cr-9Al-1Y 2431 Co-26Cr-9Al-1Y 1594
______________________________________ *Failure being defined as
the approximate number of hours of test prior t the formation of an
observable bulky, green, nickelbearing oxide which indicates that
the coating has been penetrated under the burner rig test
conditions.
* * * * *