The adherence between a ceramic thermal barrier coating and a metal bond coating is improved by ion sputtering a ceramic film on the bond cost. A ceramic thermal barrier coating is then plasma-sprayed onto this primer film. This improves the integrity and strength of the interface between the plasma-sprayed ceramic layer and metallic bond coat which insures stronger adherence between the metal and the ceramic

Bill, R. C.

Sovey, J. S.

English

NASA Technical Reports Server

[111 4,335,190 
[45] Jan, 15, 1982 
THERMAE BARRIER COATING SYSTEM 
HAVING IMPROVED ADHESION 
Inventors: Robert @. Bill, Rocky River; James 
S.  Sovey, Strongsville, both of Ohio 
Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Appl. No.: 229,233 
Filed: Jan. 28, B981 
Pnt. C1.3 ....................... B32B 15/04; B21D 39/00 
US.  GI. .................................... 428/623; 428/633; 
428/678; 427/34; 427/405; 427/419.2; 427/423 
Field of Search ...................... 427/34, 405, 419.2, 
427/423; 428/404,633, 652, 654, 667,661, 678, 
679, 685, 623 
References Cited 
US. PATENT DOCUMENTS 
3,192,892 1,4965 Hanson et al. .................... 427/38 X 
3,287,243 11/1966 Ligenza ............................... 204/192 
3,927,223 12/1975 Takabatake et al. ................. 427/34 
3,976,809 8/1976 Dowel1 .................................. 427/34 
3,977,660 8/1976 Nakahira ........................... 427/34 X 
3,989,872 11/1976 Ball ................................... 427/34 X 
4,055,705 10/1977 Stecura et al. .................... 427/34 X 
4,248,940 2/1981 Goward et al. .................. 427/34 X 
4,273,824 6/1981 McComas et al. ............... 427/34 X 
Primary Examiner-Michael R. Eusignan . 
Attorney, Agent, or Firm-Norman T. Musial; John R. 
Manning; Gene E. Shook 
1571 ABSTRACT 
This invention is directed to an improved thermal bar- 
rier system by improving the adherence between a ce- 
ramic thermal barrier coating and a metal bond coating. 
First a primer film is deposited on the bond coat by ion 
sputtering a ceramic film thereon. A ceramic thermal 
barrier coating is then plasma-sprayed onto this primer 
film. This improves the integrity and strength of the 
interface between the plasma-sprayed ceramic layer and 
metallic bond coat which insures stronger adherence 
between the metal and the ceramic. 
10 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19830023584 2020-03-22T01:21:34+00:00Z
1 
4,3 3 5,190 
2 
ened alloys, composites, and directional eutectics may 
THERMAL BARRIER COATING SYSTEM be protected in accordance with the invention. 
HAVING IMPROVED ADHESION The metallic bond coating of NiCrAlY or CoCrAlY 
is preferably deposited on the surface of the substrate by 
DESCRIPTION 5 plasma spraying as described in U.S. Pat. No. 4,055,705. 
However, it is contemplated that cladding, slurry spray, 
and sintering may be used for applying the metallic 
ORIGIN OF T H E  INVENTION 
bond coating to the substrate. A bond coating of NiCr- 
ees of the United States Government and may be manu- AIY having a thickness between about 0.003 inches and 
factured and used by or for the Government for govern- 10 0.007 inches has given satisfactory results. 
mental purposes without the Payment of any royalties A plasma spray deposited metallic bond coating of 
thereon or therefor. NiCrAlY applied to a metal substrate provided a test 
surface to be coated. Sputter deposition of yttria stabi- 
lized zirconia was performed using a I O  cm diameter TECHNICAL FIELD 
This invention is concerned with thermal barrier 15 argon ion beam from an electron bombardment ion 
coating systems which utilize ceramic coatings on me- source of the type developed from electric propulsion 
t a l k  substrates for low thermal conductivity. The in- technology. Such an ion source is described in “Ad- 
vention is particularly directed to strengthening the vanced in Electronics and Electron Physics” by H. R. 
adherence of the coatings by improving the integrity of Kaufman, vol. 36, pages 365-373. Beam extraction was 
the interfaces between the plasma-sprayed ceramic lay- 20 accomplished by a dished, two-grid ion optics system. 
ers and the metallic bond coats employed in plasma- Such a system is described in AIAA Paper No. 76-1017 
sprayed thermal barrier coating systems. entitled “A 30 cm Diameter Argon Ion Source”. Neu- 
Thermal barrier coating systems of the type de- tralization of the ion beam was achieved by using a 
scribed in U.S. Pat. No. 4,055,705 utilize a ceramic plasma bridge neutralizer. 
material that is plasma-spray deposited directly onto a 25 This electron bombardment ion source was located in 
The invention described herein was made by employ- 
plasma-sprayed metallic bond coat. Several problems 
have been encountered in using these coatings. For  
example, the molten ceramic particles that impinge onto 
the metallic bond coat are rapidly quenched on the side 
adjacent to  the bond coat. This results in a tendency to 
“peel-up” as the solidification front propogates through 
the particles. Also, the adhesive bond that forms be- 
tween the ceramic particles and the metallic bond coat 
surface is inherently weaker than a ceramic/ceramic 
cohesive bond. 
BACKGROUNDART 
Takabatake et a1 U.S. Pat. Nos. 3,927,223, Dowel1 
3,976,809, and Nakahira 3,977,660 are all directed to  
plasma spraying substrates, which are preferably metal- 
lic with a ceramic primer coat. Thereafter, a ceramic 
finish coat is applied by plasma spraying. 
Hanson et a1 U.S. Pat. Nos. 3,192,892 and Ligenza 
3,287,243 describe concepts for coating substrates, 
which are preferably metallic, with ceramic materials 
deposited by sputtering. However, neither of these pa- 
tents is concerned with depositing on the sputter coated 
ceramic material a second ceramic coat which is 
sprayed by a plasma jet. 
DISCLOSURE OF INVENTION 
According to the present invention metallic bond 
coatings are deposited on the surfaces of metal sub- 
strates which are to be protected. A primer film of a 
ceramic material is sputter-deposited onto the metallic 
bond coating. A ceramic thermal barrier coating is then 
plasma sprayed onto the primer film. In a more narrow 
aspect, the metallic bond coat is first cleaned by ionic 
bombardment. The  primer coat of ceramic material is 
then deposited by sputtering in the presence of oxygen 
which results in reactive sputtering. 
DETAILED DESCRIPTION OF T H E  
INVENTION 
As previously described a metal substrate, such as a 
turbine blade, is covered with a metallic bond coating. 
The metal substrate is preferably a nickel-base or a 
cobalt-base superalloy. HowJever, dispersion-strength- 
a vacuum facility which was sufficiently large to mini- 
mize back sputtered facility material from contaminat- 
ing the surfaces. The pressure of the vacuum facility 
was changed periodically during operation of the ion 
A sputter target was initially ion sputter cleaned for 
about 2.5 hours at an ion beam energy of about 1200 eV 
and an ion current density of about 0.5 mA/cm2. The 
pressure in the vacuum facility was about 5 x 1 0 - 5  torr. 
The substrate was then outgassed at a pressure of 
5 x  10-7 torr. This outgassing lasted for about 45 min- 
utes. The sputter target was then ion sputter cleaned 
again for about 5 minutes. The substrate was ion- 
cleaned for about 5 minutes at 1200 eV and 0.5 
The zirconia sputter target had a diameter of about 15 
centimeters and was positioned about 15 centimeters 
from the ion source at an angle of about 45” with respect 
to the ion beam. The metal substrate having the bond 
45 coating plasma sprayed thereon was positioned in the 
vacuum facility outside of the ion beam envelope and 
parallel to the sputter target. The substrate was sepa- 
rated from this target by about 15 centimeters. Air was 
introduced into this vacuum chamber until the pressure 
50 reached 1 x 10-3 torr. The  zirconia was sputter-depos- 
ited at 1300 eV and 0.5 mA/cmZ for about 18: hours. 
This produced a zirconia film having a thickness of 
about 1.5 pm. The air was partially disassociated and 
ionized by electrons in the ion source discharge cham- 
55 ber and by ions in the beam which provided free oxygen 
to enhance film stoichiometry. 
The substrate having the metal bond coating and 
primer film thereon was removed from the vacuum 
facility. A ceramic thermal barrier coating was then 
60 deposited on the primer film by plasma spraying in the 
manner described in U.S. Pat. No. 4,055,705. 
Each test sample was tested in a cyclic thermal shock 
rig. Thermal cycles were imposed on the samples until 
spalling of the plasma-sprayed ceramic layer occurred. 
65 These tests demonstrated that the plasma-sprayed yttria 
stabilized zirconia was more strongly adherent to plas- 
ma-sprayed NiCrAIY bond coated substrates that had 
been sputter-primed with yttria stabilized zirconia than 
30 source. 
35 
40 mA/cm*. 
4,335,190 
3 4 
to  otherwise similar specimens without the sputtered 2. The thermal barrier coating system of claim 1 
prime coat, one configuration of the invention, a five wherein said primer film.and said ceramic thermal bar- 
to six fold improvement in cyclic thermal shock life was rier coating are the Same 
3. The thermal barrier coating system of claini 2 demonstrated for specimens that had been sputter- 
5 wherein said primer film is stabilized with a material 
primed. selected from the group consisting of yttria, calcia, and 
In an alternate embodiment of the invention R F  sput- magnesia and has a thickness of about 1.5 pm. 
ter deposition of the yttria stabilized zirconia or other 4. The thermal barrier coating system of claim 3 
ceramic material is used. In such an embodiment sputter wherein said primer film and said thermal barrier coat- 
deposition is carried O u t  in an argon environment at IO ing are selected from the group consisting of ZrOz-Yz 
about 15 p m  Hg absolute pressure, 250 w forward 
target and substrate yielding a ZrOz deposition rate of 
about 0.25 pm/hour. 
While yttria stabilized zirconia (ZrOz y203) has 
given satisfactory results, the ceramic to be deposited 
may be calcia stabilized zirconia (ZrOr-CaO) or magne- 
sia stabilized zirconia (ZrO2 Mg 0) or, in general, any 
ceramic material. Also, the metallic substrate may be 20 
other than a plasma-sprayed metallic bond coating. It is 
contemplated that any specifically roughened, porous, 
of otherwise prepared metallic surface may be used. 
been described it will be appreciated that various modi- 
fications may be made without departing from the spirit 
of the, invention or the scope of the subjoined claims. 
Zr02-MgO* and Zr02-Ca0. 
power to a 15 cm target, 3.5 cm separation between 5. the thermal barrier coating system of 
wherein said primer film and said thermal barrier coat- 
ing are yttria stabilized zirconia, 
6. A method of coating surfaces of nickel-base and 
cobalt-base superalloys, dispersion-strengthened alloys, 
composites, and directional eutectics comprising the 
steps of 
depositing a bond coating of an alloy selected from 
the group consisting of nickel-base alloys and CO- 
balt-base alloys on said surfaces, 
Sputter depositing a primer film of a ceramic material 
onto said bond coating, and 
plasma spraying a thermal barrier coating of a ce- 
ramic material Onto said primer coating whereby 
the integrity and strength of the interface between 
said primer film and said thermal barrier coating 
are improved, thereby improving the adherence of 
the thermal barrier coating systems to said surfaces. 
7. The method of coating metal surfaces as claimed in 
claim 6 wherein the ceramic material of the primer film 
is sputter-deposited to a thickness of about 1.5 pm, and 
the Same ceramic material is then plasma sprayed 
el- and cobalt-based superalloys, dispersion- onto said primer film thereby forming the thermal 
StrengtheIIed alloys, composites, and directional 35 barrier coating system having improved adherence 
eutectics, at the interface. 
a bond coating consisting essentially of a material 8. The method of coating metal surfaces as claimed in 
selected from the group consisting of NiCrAlY and claim 7 wherein the ceramic material is zirconia stabi- 
CoCrAlY covering said substrate, said bond coat- lized wi th  another Oxide. 
9. The method of coating metal surfaces as claimed in ing having an ion sputter cleaned surface, 
claim 8 wherein said bond coating is ion cleaned prior a primer film consisting essentially of ZrO2 stablized to sputter-depositing said ceramic primer film, 
with another oxide bonded to said textured surface, 10. The method of coating metal surfaces as claimed 
and in claim 9 wherein the zirconia is sputter-deposited at 
a ceramic thermal barrier coating bonded to said 45 1300 eV and 0.5 mA/cm2 for about 18.5 hours. 
primer film. 
15 
While several embodiments of the invention have 25 
We claim: 
1, A coated article of manufacture having a thermal 30 
a substrate selected from the group consisting of nick- 
barrier coating system comprising 
40 
* * * * *  
50 
55 
60 
65 


Thermal barrier coating system having improved adhesion

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