A substrate, such as a turbine blade, vane, or the like, which is subjected to high temperature use is coated with a base coating of an oxide dispersed, metallic alloy (cermet). A top coating of an oxidation, hot corrosion, erosion resistant alloy of nickel, cobalt, or iron is then deposited on the base coating. A heat treatment is used to improve the bonding. The base coating serves as an inhibitor to interdiffusion between the protective top coating and the substrate. Otherwise, the protective top coating would rapidly interact detrimentally with the substrate and degrade by spalling of the protective oxides formed on the outer surface at elevated temperatures

Gedwill, M. A.

Glasgow, T. K.

Levine, S. R.

English

NASA Technical Reports Server

States Patent [191 
Gedwill et al. 
1541 OVERLAY METALLIC-CERMET ALLOY - -  
COATING 
[75] Inventors: 
[73] Assignee: 
[21] Appl. No.: 
[22] Filed: 
SYSTEMS 
Michael A. Gedwill, North Olmsted; 
Stanley R. Levine; Thomas K. 
Glasgow, both of Rocky River, all of 
Ohio 
The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
403,378 
Jul. 30, 1982 
[51] Int. C l . 3  .............................................. B32B 15/00 
[52] US. c1. .................................... 428/639; 428/564; 
428/678; 416/241 R 
[58] Field of Search ............... 428/629, 632, 633, 639, 
428/678-685, 552, 553, 564; 416/241 R, 241 B 
t561 References Cited 
U.S. PATENT DOCUMENTS 
3,864,093 2/1975 
3,890,456 6/1975 
4,101,713 7/1978 
4,124,737 11/1978 
4,145,481 3/1979 
4,198,442 4/1980 
Wolfa .................................. 428/652 
Dils ..................................... 428/670 
Hirsch et al. ....................... 428/554 
Wolfa et al. ........................ 428/679 
Gupta et al. ........................ 428/678 
Gupta et al. .......................... 427/34 
4,248,940 2/1981 Goward et al. ..................... 428/633 
4,303,737 12/1981 Litchfield et al. .................. 428/406 
4,330,575 5/1982 Litchfield et al. .................... 75/252 
4,314,007 2/1982 Gessinger et al. .................. 428/614 
FOREIGN PATENT DOCUMENTS 
1352319 5/1974 United Kingdom ................ 428/632 
Primary Examiner-Michael L. Lewis 
Attorney, Agent, or Firm-Norman T. Musial; John R. 
Manning; Gene E. Shook 
t571 ABSTRACT 
A substrate, such as a turbine blade, vane, or the like, 
which is subjected to high temperature use is coated 
with a base coating of an oxide dispersed, metallic alloy 
(cermet). A top coating of an oxidation, hot corrosion, 
erosion resistant alloy of nickel, cobalt, or iron is then 
deposited on the base coating. A heat treatment is used 
to improve the bonding. The base coating serves as an 
inhibitor to interdiffusion between the protective top 
coating and the substrate. Otherwise, the protective top 
coating would rapidly interact detrimentally with the 
substrate and degrade by spalling of the protective ox- 
ides formed on the outer surface at elevated tempera- 
tures. 
8 Claims, 5 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19840025484 2020-03-22T10:14:28+00:00Z
U.S. Patent May 1, 1984 Sheet 1 of 2 4,446,199 
FIG. I 
4 
GAIN 3 F  LL 
SPEC1 FI C 
WEIGHT 
CHANGE, 
Mg/Cm2 
LOSS 
; 
100 200 300 400 500 
EXPOSURE TIME, HR 
FIG. 2 
-20 
GAIN 
WEIGHT 
CHANGE, 
Mg 
LOSS 32 
100 200 300 
EXPOSURE TIME, HR 
FIG. 5 
atenk May 1, 1984 Sheet 2 of 2 4,446,199 
N i- 18C r -12AI -0.3Y 
Ni-l ICr-6AI- 
0.3Y-40Y20 3 f 
MA-754 
FIG. 3 
FIG. 4 
4,446,199 
1 
OVERLAY METALLIC-CERMEX ALLOY 
COATING SYSTEMS 
DESCRIPTION 
ORIGIN O F  THE INVENTION 
The invention described herein was made by employ- 
ees of the U.S. Government and may be manufactured 
and used by or for the Government for governmental 
purposes without the payment of any royalties thereon 
or therefor. 
TECHNICAL FIELD 
This invention relates to protective coating systems 
for metallic surfaces that are subjected to high tempera- 
ture uses, such as the surfaces of turbine blades, vanes, 
and the like. The useful lives of current and new nickel 
and cobalt base superalloys in hot section air foils of 
advanced gas turbine engines are often limited by coat- 
ing wearout. The new oxide dispersion strengthened 
(ODS) superalloys have the strength potential for thou- 
sands of hours of use at temperatures up to 1200" C. The 
major limiting factors are oxidation and hot corrosion. 
Even though the endurance of these alloys has been 
improved by coating processes which utilize aluminide 
diffusion coatings and single-step overlay coatings, only 
interim short-term solutions to the problems have been 
obtained. The protection ability of these coatings rap- 
idly degrades at temperatures contemplated for ad- 
vanced jet engines primarily because of diffusional in- 
stability between the coating and an oxide dispersion 
strengthened substrate. It has been found that protec- 
tive coatings of alloys containing aluminum over sub- 
strates of superalloys containing no aluminum were 
degraded because aluminum from the coatings diffused 
into the substrate. 
BACKGROUND ART 
Gupta et al. U.S. Pat. No. 4,145,481 discloses a pro- 
cess for producing elevated temperature corrosion re- 
sistant metal articles. This process employs an overlay 
of a ductile alloy of a composition normally resistant to 
corrosion at elevated temperatures and a corrosion- 
resistant outer layer of aluminide or metal. Thearticle is 
then heat treated at high pressure to e l i i a t e  coating 
porosity. 
Gupta et al. U.S. Pat. No. 4,198,442 is directed to a 
method for producing metal articles that are resistant to 
corrosion at elevated temperatures. The method utilizes 
a ductile inner layer of a cobalt, iron, or nickel alloy and 
an outer layer that is highly resistant to corrosion at 
elevated temperatures. The inner and outer layers form 
a composite coating. 
In Hirsch et al. US. Pat. No. 4,101,713 a superalloy 
substrate is flame sprayed with powders of chromium 
and at least one element selected from iron, cobalt, and 
nickel to form a single layer coating. This coating may 
contain aluminum, carbon, yttrium, or the rare earth 
elements. In an alternate embodiment the coating pow- 
ders include from about 0.5 to about 5 percent by vol- 
ume of dispersed particles for dispersion strengthening. 
Goward et al. U.S. Pat. No. 4,248,940 describes a 
thermal barrier coating system for nickel-and cobalt- 
base suDerallovs which comDrises a zirconia-based ce- 
5 
10 
15 
20 
25 
30 
35 
2 
alloy is a bond coating. The materials of the bond coat- 
ing and thermal barrier coating are graded from the 
surface of the superalloy substrate to the outer surface 
of the ceramic coating. 
Gessinger U.S. Pat. No. 4,314,007 is concerned with 
producing a composite shaped article consisting of a 
reinforced core of a heat resistant oxide-dispersion 
hardened metal or alloy which is encapsulated within 
and bonded to a heat resistant metal or alloy cladding. 
DISCLOSURE OF INVENTION 
According to the present invention a substrate is 
coated with a base coating of an oxide dispersed, metal- 
lic alloy (cermet). A top coating of an oxidation, hot 
corrosion, erosion resistant alloy of nickel, cobalt, or 
iron is then deposited on the base coating. A heat treat- 
ment is used to improve the boding. 
The base coating serves as an lllhibitor to interdiffu- 
sion between the protective top coating and the sub- 
strate. Otherwise, the protective top coating would 
rapidly interact detrimentally with the substrate and 
rapidly degrade by spalling of the protective oxides 
formed on the outer surface at elevated temperatures. 
However, a top coating successfully applied in accor- 
dance with the present invention yields an excellent 
diffusionally stable, protective covering. 
BRIEF DESCRIPTION OF THE DRAWINGS 
The details of the invention will be more fully de- 
scribed when taken with the accompanying drawings in 
which 
FIG. 1 is a vertical sectional view of an overlay met- 
allic-cermet alloy coating system constructed in accor- 
dance with the present invention, 
FIG. 2 is a graph of cyclic furnace oxidation of a 
coated superalloy, 
FIG. 3 is a photomicrograph at l00X magnification 
of sprayed and heat treated coating system before fur- 
40 nace oxidation, 
FIG. 4 is a photomicrograph at lOOX magnification 
of the coating system shown in FIG. 3 after it has been 
cyclic furnace oxidized, and 
FIG. 5 is a curve showing cyclic Mach 0.3 burner rig 
45 oxidation of coated and uncoated superalloys. 
BEST MODE FOR CARRYING OUT THE 
INVENTION 
Referring now to FIG. 1 there is shown a substrate 10 
that is coated in accordance with the present invention. 
The substrate 10 is preferably of a nickel-or cobalt-base 
superalloy that is to be used in hot section air foils of gas 
turbine engines. 
A base coating 12 is initially deposited on the sub- 
strate 10. The base coating 12 comprises an intermediate 
layer of an oxide dispersed, metallic alloy (cermet) se- 
lected from the group consisting of nickel-, cobalt-, and 
iron-base alloys and refractory oxide. 
A top coating 14 is subsequently deposited on the 
base coating 12. The top coating 14 comprises an oxida- 
tionhot-corrosion/erosion resistant alloy selected from 
the group consisting of nickel-, cobalt-, and iron-base 
allovs. 
55 
60 
r m i c  
num, and yttrium with materials selected from a group 
including iron, cobalt, nickel, and nickel-cobalt. The 
ceramic material is a thermal barrier coating while the 
is applied over an-alloy of chromium, alumi- 65 The coated substrate is then heat treated to improve 
bonding. This heat treatment comprises heating the 
coated substrate at 1080" C. for four hours in an inert 
atmosphere. 
4,446,199 
3 
For optimum protection the matrices of the top coat- 
ing 14 and base coating 12 should have a stable, fine 
grain structure. Also the thickness of the top coating 14 
should be in the range of 50% to 70% of the total thick- 
ness of the combined top coating 14 and base coating 12. 
Both the base coating 12 and the top coating 14 are 
preferably applied by arc-plasma spraying the coating 
powders in ambient air at arc gas velocities in the range 
of subsonic to Mach 2.0. Alternately, the coatings 12 
and 14 may be plasma sprayed in a chamber with either 
an inert gas or a vacuum environment. It is further 
contemplated that the coating powders may be arc- 
plasma sprayed in a reactive gas environment. 
The cermet powders for the base coating are pre- 
pared using a mechanical alloying process. The volume 
percent of the dispersed oxide in the cermet coating is in 
the range of about 10% to about 75%. All other compo- 
sitions are expressed in weight percents. 
An oxide dispersion strengthened superalloy having a 
nominal composition of Ni-20 Cr-1.4 Fe-2Y203 and 
known commercially as MA-754 was coated in accor- 
dance with the present invention. The coating system 
consisted of a base coating of Ni- 1 lCr-6A1-0.3Y- 
my203 covered by a Ni-18Cr-12A1-0.3Y top coating. 
This superalloy protected by the alloy plus cermet coat- 
ing was subjected to a cyclic furnace oxidation test at 
1150" C. The coating remained adherent throughout the 
test. The specific weight change in millograms per 
square centimeter plotted against exposure time in 
hours is illustrated by the line 20 in FIG. 2. 
Two other coatings were applied and similarly tested. 
The first coating was aluminized electron-beam physi- 
cal vapor-deposited Ni-20Cr-5A1-0.3Y. This coating 
remained adherent throughout the test. The results of 
this test are shown in line 22 of FIG. 2. Similarly, an 
electron-beam physical vapor deposited Ni-18Cr-12Al- 
0.3Y coating was tested. The coating blistered during 
the test. The results of this coating test are shown in line 
24 of FIG. 2. 
The results illustrated in FIG. 2 show that the alloy 
plus cermet coating provides cyclic furnace oxidation 
protection for MA-754 of over 500 hours at 1150" C. 
compared to about 100 hours for the other two coat- 
ings. This is about a 5-fold improvement. 
FIGS. 3 and 4 show typical cross-sectional micro- 
structures before and after furnace oxidation. Both pho- 
tomicrographs are of arc-plasma sprayed Ni -18 Cr- 
12A1-0.3Y plus Ni-l1Cr-6A1-0.3 Y-40 Y203 on a MA- 
754 substrate. The photomicrographs are at l00X mag- 
nification. A comparison of FIG. 3 which is after the 
substrate was sprayed and heat treated for four hours at 
1080" C. in argon and FIG. 4 which is after the coated 
substrate was cyclically furnace oxidized for 500 hours 
at 1150" C. indicates that no serious coating degradation 
had occurred during the 500 hour oxidation test. 
Several coatings on oxide dispersion strengthened 
superalloys were also evaluated in cyclic oxidation at 
1150" C. in a Mach 0.3 burner rig which simulates a jet 
engine environment. The burner rig results plotted as 
weight change against exposure time for coated and 
uncoated oxide dispersion strengthened superalloys are 
shown in FIG. 5. The test results for an arc plasma 
sprayed Ni-18 Cr-12A1-0.3 Y plus Ni-17Cr-10 A1-0.5 Y- 
9Y203 coating on an MA-754 substrate are shown in 
line 30. 
The test results of an arc plasma sprayed Ni-18 Cr-12 
A1-0.3 Y coating on an MA-754 substrate are shown in 
line 32. The line 34 sets forth the results of an electron 
4 
beam physical vapor deposited Ni-18 Cr-12A1-0.3 Y 
coating on MA-754. This coating blistered after a rela- 
tively short exposure time. Line 36 show the results of 
testing uncoated MA-754. 
Line 38 illustrates the results of testing an uncoated 
substrate of commercially-known MA-755 E. This ma- 
terial has a nominal composition of Ni-15 Cr-4.5 A1-5.5 
W-3.5 Mo-3Ti-2.5 Ta-1.1 Y203. The same substrate 
coated with a commercial aluminized coating is shown 
It is evident the alloy plus cermet coating provided at 
least 250 hours of cyclic oxidation protection in the 
burner rig. Compared to one of the best commercial 
aluminide coatings, shown in line 40, the alloy plus 
l5 cermet coating of line 30 showed about a 150-hour 
improvement. By increasing the oxide content above 9 
weight percent in the cermet coatings, significant im- 
provements are expected. 
Although the preferred embodiment of the invention 
2o has been disclosed and described it will be appreciated 
that various modifications may be made to the coating 
system without departing from the spirit of the inven- 
tion or the scope of the subjoined claims. It should also 
be recognized that the invention can be used as the bond 
25 coating system in what is known as a thermal barrier 
coating. 
5 
10 in line 40. 
We claim: 
1. A coated article of manufacture comprising 
a substrate selected from the group consisting of nick- 
el-base alloys and cobalt-base alloys, 
a cermet layer of an oxide dispersed metallic alloy 
having nominal composition in weight percents of 
about 11% to about 17% chromium, about 6% to 
about 10% aluminum, about 0.3% to about 0.5% 
yttrium, and the remainder nickel containing about 
9% to about 40% yttrium oxide covering said sub- 
strate, said dispersed oxide comprising between 
about 10 and about 75 volume percent of said cer- 
a protective coating of an alloy selected from the 
group consisting of nickel-, cobalt-, and iron-base 
alloys covering said cermet layer. 
2. A coated article of manufacture as claimed in claim 
45 wherein the thickness of the protective coating is about 
50% to about 70% of the total thickness of the com- 
bined protective coating and cermet layer. 
3o 
35 
40 met layer, and 
3. A coated article of manufacture comprising 
a substrate having a nominal composition in weight 
a cermet layer of an oxide dispersed metallic alloy 
selected from the group consisting of nickel-, co- 
balt-, and iron-base alloys and a refractory oxide 
covering said substrate, said dispersed oxide com- 
prising between about 10 and about 75 volume 
percent of said cermet layer, and 
a protective coating having a nominal composition in 
weight percent of Ni-18Cr-12A1-0.3Y covering 
said cermet layer, said protective coating having a 
thickness between about 50% and about 70% of the 
total thickness of the combined protective coating 
and cermet layer. 
4. A coated article of manufacture as claimed in claim 
3 wherein the cermet layer has a nominal composition 
65 in weight 25 percents of Ni-1 1 Cr-6 A1-0.3Y - 40 YzO3. 
5. A coated article of manufacture as claimed in claim 
3 wherein the cermet layer has a nominal composition 
in weight percents of Ni - 17 Cr-10 A1 - 0.5Y - 9Y203. 
50 percent of Ni-20Cr-l.4Fe-2Y203, 
55 
60 
5 
4,446,199 
6 
6. In a coated article of manufacture of the type 
wherein a substrate selected from the group consisting 
of nickel-base and cobalt-base alloys is protected by 
coating of an alloy selected from the group consisting of 
nickel-, cobalt-, and iron-base alloys, the improvement 5 
comprising 
a cermet iayer of an oxide dispersed metallic alloy 
about 6% 
between said substrate and said coating to inhibit 
interdiffusion between said substrate and said coat- 
ing, said dispersed oxide comprising at least nine 
weight percent of said cermet layer. 
in claim 
6 wherein the dispersed oxide comprises about 10 to 
of about 11% to about 17% 8. A coated article of manufacture as claimed in claim 
to about 10% aluminum, about 0.3% to about 0.5% 10 6 wherein the thickness of the coating is about 50% to 
yttrium, and the remainder nickel and a refractory about 70% of the total thickness of the combined pro- 
oxide having a nominal composition in weight 
7. A coated article of manufacture as 
having a nominal composition in weight percents about 75 percent of said layer* 
tective coating and cermet layer. 
percent of about 9% to about 40% yttrium oxide * * * * *  
15 
20 
25 
30 
35 
40 
45 
50 
55 
60 
65 
UNITED STATES PATENT OFFICE 
CERTIFICATE OF CORRECTION 
PATENT NO. 4,446,199 
DATED May 1, 1984 
I N V E N T O K ( S )  Michael A. Gedwill e t  a1 
are hereby corrected as shown below 
I t  I S  certif ied that error appears in the above-identified patent and that said Letters Patent 
Column 4 ,  l i n e  43,  a f t e r  "claim" insert - - I - -  
5igncd and 9calcd this 
Twenty-eighth Day o f  Augur 1984 
Attest: 
Attesting Officer 
GERALD J .  MOSSINGHOFF 
Commissitmrr o j hrtnts and Tmdtmwks 


Overlay metallic-cermet alloy coating systems

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