A base layer of an oxide dispersed, metallic alloy (cermet) is arc plasma sprayed onto a substrate, such as a turbine blade, vane, or the like, which is subjected to high temperature use. A top layer of an oxidation, hot corrosion, erosion resistant alloy of nickel, cobalt, or iron is then arc plasma sprayed onto the base layer. A heat treatment is used to improve the bonding. The base layer serves as an inhibitor to interdiffusion between the protective top layer and the substrate. Otherwise, the 10 protective top layer 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

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United States Patent [191 
Gedwill et al. 
11 11 4,451,496 
[45] May 29, 1904 
[54] COATING WITH OVERLAY 
[75] Inventors: Michael A. Gedwill, North Olmsted; 
Stanley R. Levine; Thomas K. 
Glasgow, both of Rocky River, all of 
Ohio 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
METALLIC-CERMET ALLOY SYSTEMS 
[73] Assignee: The United States of America as 
[21] Appl. No.: 456,460 
[22] Filed: Jan. 7,1983 
Related U.S. Application Data 
[62] Division of Ser. No. 403,378, Jul. 30, 1982, Pat. No. 
4,446,199. 
[51] Int. Cl.3 ............................................... B05D 1/08 
[52] U.S. C1. ...................................... 427/34; 427/405; 
427/419.2; 428/632 
[58] Field of Search .............. 427/34, 423, 405, 419.2, 
427/629; 428/632, 678, 679, 682 
[561 References Cited 
U.S. PATENT DOCUMENTS 
3,864,093 2/1975 Wolfla 
3,890,456 6/1975 Dils ....... ................. 428/670 
4,005,989 2/1977 Preston ............................... 428/678 
4,101,713 7/1978 Hirsch et al. 
4,124,737 11/1978 Wolfla et al. ....................... 428/679 
4,145,481 3/1979 Gupta et al. ........................ 428/618 
4,198,442 4/1980 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 
4,314,007 2/1982 Gessinger ............................ 428/614 
4,330,575 5/1982 Litchfield et al. .................... 75/252 
FOREIGN PATENT DOCUMENTS 
1352319 5/1974 United Kingdom ................ 428/632 
Primary Examiner-John H. Newsome 
Attorney, Agent, or Firm-Norman T. Musial; John R. 
Manning; Gene E. Shook 
1571 ABSTRACT 
A base layer of an oxide dispersed, metallic alloy (cer- 
met) is arc-plasma sprayed onto a substrate, such as a 
turbine blade, vane, or the like, which is subjected to 
high temperature use. A top layer of an oxidation, hot 
corrosion, erosion resistant alloy of nickel, cobalt, or 
iron is then arc-plasma sprayed onto the base layer. A 
heat treatment is used to improve the bonding. The base 
layer serves as an inhibitor to interdiffusion between the 
protective top layer and the substrate. Otherwise, the 
protective top layer would rapidly interact detrimen- 
tally with the substrate and degrade by spalling of the 
protective oxides formed on the outer surface at ele- 
vated temperatures. 
19 Claims, 5 Drawing Figures 
Ni-I8Cr- 
IZAI-0.3Y 
Ni-IICr-GAI- 
0.3Y-40Yz03 
MA-754 
U.S. Patent May 29, 1984 Sheet 1 of 2 4,45 1,496 
FIG. I 
EXPOSURE TIME, HR 
FIG. 2 
GAl N 
WEIGHT 
CHANGE, 
Mg 
LOSS 32 
100 200 300 
EXPOSURE TIME, HR 
FIG. 5 
U.S. Patent May 29,1984 Sheet 2 of 2 4,45 1,496 
i 
NI-18Cr- 
I2 AI-0.3Y 
Ni-l ICr-6AI- 
0.3Y-40Y203 
MA9754 
FIG. 3 
FIG. 4 
4,45 1, 
QVERLAY METALLIC-CERMET 
ALLOY SYSTEMS 
DESCRIPTION 5 
Origin of 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 10 
purposes without the payment of any royalties thereon 
or therefor. 
STATEMENT OF COPENDENCY 
403,378 which was fded July 30, 1982 now U.S. Pat. 
No. 4,446,199. 
TECHNICAL FIELD 
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- 25 
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. 
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- 35 
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 coating of alloys containing aluminum over sub- 
strates of superalloys containing no aluminum were 40 
degraded because aluminum from the coating diffused 
into the substrate. 
BACKGROUND ART 
This application is a division of application Ser. No. 15 
This invention relates to prot:ctive coating systems 20 
Even though the endurance of these alloys has been 30 
496 
2 
Goward et a1 U.S. Pat. No. 4,248,940 describes a 
thermal barrier coating system for nickel- and cobalt- 
base superalloys which comprises a zirconia-based ce- 
ramic that is applied over an alloy of chromium, alumi- 
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 
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 O F  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 bonding. 
The base coating serves as an inhibitor 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, 
Gupta et a1 U.S. Pat. No. 4,145,481 discloses a pro- 45 FIG. 3-k a PhOtomicrograPh at loox magnification 
of a sprayed and heat treated coating system before 
furnace oxidation, 
FIG. 4 is a photomicrograph at 100X magnification 
of the mating system shown in FIG. 3 after it has been 
FIG. 5 is a curve showing cyclic Mach 0.3 burner rig 
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. The article is 50 cyclic furnace oxidized, and 
then heat treated at high pressure to eliminate 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 55 
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. 
substrate is flame sprayed with powders of chromium 
mechanically alloyed with at least one element selected 
from iron, cobalt, and nickel to form a single layer coat- 
ing. This coating may contain aluminum, carbon, yt- 
trium, or the rare earth elements. In an alternate em- 65 iron-base alloys and a refractory oxide. 
bodment the coating powders include from about 0.5 to 
about 5 percent by volume of dispersed particles for 
dispersion strengthening. 
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 
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 
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 
In Hirsch et al U.S. Pat. No. 4,101,713 a superalloy 60 turbine engines. 
4,45 1,496 
4 
the group conaisti of nickel-, cobalt-, and iron-base uncoat spersion s~rengthened superalloy8 are 
dloyR, . The bet results for an arc plasma 
12A1-0.3Y plus Ni- 17Cr- 10A1-0.5Y- 
an MA-754 substrate are shown in 
The test results of an arc plaema eprayed Ni-lllCr. 
12A1-0.3Y coatin on an MA-754 substrate are shown in 
line 32. The line 4 sete forth the results of an electron 
10 coating on MA.754. This coating bliatered after a rela- 
tively short expoeure time. Line 36 ehow the results of 
testing uncoated MA-754. 
substrate of commercially-known MA-755 E. This ma- of subsonic to Mach 2.0. Alternately, the coatings 12 15 terial has a nomind composition of ~ i - 1 5 ~ ~ ~ 4 . 5 A l .  
an inert gas or a vacuum environment. It is further coated with a commercial coating is shown 
contemplated that the coating powders may be arc- in line 
It is evident the alloy plus cermet coating provided at plasma sprayed in a reactive gas environment. 
described in the aforementioned US. Pat. No. 4,101,713 aluminide coatings, shown in line the alloy plus 
oxide in the cermet coating is in the range of about 10% improvement. By increasing the oxide content about to about 75%. All other compositions are expressed in 25 weight percent in the cermet significant im. weight percents. provements are expected. 
nominal composition of Ni-2OCr- 1.4Fe-2Yz03 and 
known commercially as MA-754 was coated in aCCOr- has been disclosed and described it will be appreciated 
consisted of a base coating of ~ i - 1 1 ~ ~ - 6 ~ l - ~ . 3 ~ -  system without departing from the spirit of the inven- 
4yzo3 covered by a ~ i - 1 8 ~ ~ - 1 2 ~ 1 - 0 . 3 Y  top coating. tion or the scope of the subjoined claims. It should also 
1150" C. The coating remained adherent throughout the 35 coating* 
test. The specific weight change in milligrams per 
square centimeter plotted against exposure time in 
hours is illustrated by the line 20 in FIG. 2. 
The first coating was aluminized electron-beam physi- 40 powders from the 
cal vapor-deposited Ni-20Cr-5A1-0.3Y. This coating group consisting of nickel-base, cobalt-base and 
remained adherent throughout the test. The results of iron base alloy constituents and refractory oxide 
this test are shown in line 22 of FIG. 2. Similarly, an powders, 
electron-beam physical vapor deposited Ni- 18Cr- 12A1- arc-Plasma spraying said cermet Powders onto said 
0.3Y coating was tested. The coating blistered during 45 surfaces to form a base coating having said refrac- 
the test. The results of this coating test are shown in line tory oxide dispersed therein, said dispersed oxide 
24 of FIG. 2. comprising between about 10 volume percent and 
The results illustrated in FIG. 2 show that the al!oy about 75 volume percent of said base coating, 
plus cermet coating provides cyclic furnace oxidation arc-plasma spraying powders of an alloy selected 
protection for Ma-754 of Over 500 hours at 1150" C. 50 from the group consisting of nickel-base, cobalt-base, 
compared to about 100 hours for the other two coat- and iron base alloys onto said base coating to form an 
ings. This is about a 5-fold improvement. oxidation, hot corrosion, erosion resistant top coating, 
FIGS. 3 and 4 show typical cross-sectional micro- and 
structures before and after furnace oxidation. Both pho- heat treating the Coated substrate to improve the 
tomicrographs are of arc-plasma sprayed Ni-18Cr- 55 bonding ofthe base coating and the mP coating to 
12A1-0.3Y plus Ni-l1Cr-6A1-0.3 Y-4OY2O3 on a MA- said substrate. 
754 substrate. The photomicrographs are at l00X mag- 2. A method of coating alloy substrate surfaces as 
nification. A comparison of FIG. 3 which is after the claimed in claim 1 wherein the coated substrate is heat 
substrate was sprayed and heat treated for four hours at treated at about 1080" c. in argon for about four hours. 
1080" C. in argon and FIG. 4 which is after the coated 60 3. A method of coating alloy substrate surfaces as 
substrate was cyclically furnace oxidized for 500 hours claimed in claim 1 wherein the coating powders are 
at 11 50" C. indicates that no serious coating degradation arc-plasma sprayed in an ambient air environment. 
had occurred during the 500 hour oxidation test. 4. A method of coating alloy substrate surfaces as 
Several coatings on oxide dispersion strengthened claimed in claim 1 wherein the coating powders are 
superalloys were also evaluated in cyclic oxidation at 65 arc-plasma sprayed in an inert gas environment. 
1150" C. in a Mach 0.3 burner rig which simulates a jet 5. A method of coating alloy substrate surfaces as 
engine environment. The burner rig results plotted as claimed in claim 1 wherein the coating powders are 
weight change against exposure time for coated and arc-plasma sprayed in a vacuum environment. 
rate is then heat treated 
This heat treatment comprises 
1080" C, for four hour 
atmo5phere, 
For optimum protection the matrices of the top coat- 
beam physical vapor deposited Ni. 18Cr.12Al.0.3Y 
Line 38 illustrates the results of testin 
and l4 be plasma sprayed in a chamber with either 5,5W-3.JMo.3Ti.2,5 Ta-1.1Y203, The substrate 
The powders for the base coating are Pre- 20 least 250 hours of cyclic oxidation protection in the 
pared a process Of the type burner rig, Compared to one of the best commercial 
to et The percent Of the dispersed cermet coating of line 30 showed about a 150-hour 
An Oxide dispersion strengthened superdloy having a Although the preferred embodiment of the invention 
dance with the present invention, The coating system 30 that various modifications may be made to the coating 
This superalloy protected by the alloy plus cermet coat- 
ing was subjected to a cyclic furnace oxidation test at 
be recognized that the invention can be used as the bond 
coating system in what is known as a thermal barrier 
We 
1. A method of coating nickel-base and cobalt-base 
alloy substrate surfaces comprising the steps of 
Two other coatings were applied and similarly tested. forming cermet powders by mechanicah' alloying 
4,45 1,496 
5 6 
6. A method of coating alloy substrate surfaces as p r i ~ e ~  between about 10 and about 75 volume percent of 
claimed in claim 1 wherein the coating powders are . said base coating. 
arc-plasma sprayed in a reactive gas environment. 12. A method of protecting a metallic substrate as 
7. A method of protecting a metallic substrate from claimed in claim 9 wherein the top coating is deposited 
5 by arc-plasma spraying powders selected from the oxidation, hot corrosion and erosion at high tempera- group consisting of nickel-base, cobalt-base, and iron- tures at which diffusional instability is exhibited be- base alloys onto said first 
wherein said metallic alloy coating interacts detrimen- claimed in claim 12 wherein the powders of the base 
tally with said substrate, said method comprising the 10 coating and top coating are arc plasma sprayed in an 
steps of ambient air environment. 
14. A method of protecting a metallic substrate as 
claimed in claim 12 wherein the powders of the base 
coating and top coating are arc plasma sprayed in an 
15. A method of protecting a metallic substrate as 
claimed in claim 12 wherein the powders of the base 
vacuum environment. 
16. A method of protecting a metallic substrate as 
claimed in claim 12 wherein the powders of the base 
coating and top coating are arc plasma sprayed in a 
reactive gas environment. 
17. A method Protecting a metallic substrate as 
cobalt-base, and iron- 25 claimed in claim 9 including the step of heat treating the 
18. A method of protecting a metallic substrate as 
tween a metallic alloy coating and said Substrate 13. A method of protecting a metallic substrate as 
depositing a base coating of an oxide dispersed, metal- 
lic alloy on said substrate to inhibit diffusion of 
coating material into said substrate, and 
sion, erosion resistant alloy on said base coating. 
depositing a top coating of an oxidation, hot-corro- l5 inert gas environment. 
8* A method of protecting a substrate as coating and top coating are arc plasma sprayed in a 
claimed in claim 7 wherein the substrate is a metal se- 
lected from nickel-base suPera1l0Ysl and cobalt-base 20 
superalloys. 
9. A method of protecting a metallic substrate as 
claimed in claim 8 wherein the base coating is deposited 
by arc-plasma spraying powders selected from the 
group consisting of 
of said substrate. 
claimed in claim 9 including the step of 
base alloys containing a dispersed oxide onto a surface coated substrate to improve the bonding Of the base 
coating and top coating to said substrate. 
lo. A method Of protecting a substrate as claimed in claim 17 wherein the coated substrate is heat 
30 treated at about 1080" C. in argon. 
mechanically alloying the powders prior to arc- 
11. A method protecting a metallic substrate as 
19. A method of protecting a metallic substrate as 
claimed in claim 18 wherein the coated substrate is heat 
treated for about four hours. 
plasma spraying the base coating. 
claimed in claim 10 wherein the dispersed oxide com- * * * * *  
35 
40 
45 
50 
55 
60 
65 


Coating with overlay metallic-cermet alloy systems

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