Performance of thermal barrier coatings produced by smart plasma processing
Thermal barrier coating typically comprising of bondcoat and yttrium stabilized zirconium topcoat, has been used to improve the efficiency of turbine engine by providing the capability to sustain significant temperature gradient across the coating. Alumina and zirconia composite coating was prop...
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irk-123456789-823022015-05-28T03:01:59Z Performance of thermal barrier coatings produced by smart plasma processing Kobayashi, Akira Low temperature plasma and plasma technologies Thermal barrier coating typically comprising of bondcoat and yttrium stabilized zirconium topcoat, has been used to improve the efficiency of turbine engine by providing the capability to sustain significant temperature gradient across the coating. Alumina and zirconia composite coating was proposed as a potential candidate to improve the qualities of thermal barrier coating system due to its low melting point and high hardness. The gas tunnel type plasma system, which has high energy density and also high efficiency, is useful for smart plasma processing. The characteristics of the obtained ceramic coatings such as Al₂O₃ and ZrO₂ coatings were superior to the conventional ones. The ZrO₂ composite coating has the possibility of the development of high functionally graded TBC (thermal barrier coating). In this study, the performance such as the mechanical properties, thermal behavior and high temperature oxidation resistance of the alumina/zirconia functionally graded TBCs produced by gas tunnel type plasma spraying was investigated and discussed. The results showed that the alumina/zirconia composite system exhibited the improvement of mechanical properties of thermal barrier coatings and oxidation resistance. 2006 Article Performance of thermal barrier coatings produced by smart plasma processing / Akira Kobayashi // Вопросы атомной науки и техники. — 2006. — № 6. — С. 181-185. — Бібліогр.: 13 назв. — англ. 1562-6016 PACS: 52.75.Hn; 52.77.-j http://dspace.nbuv.gov.ua/handle/123456789/82302 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Low temperature plasma and plasma technologies Low temperature plasma and plasma technologies |
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Low temperature plasma and plasma technologies Low temperature plasma and plasma technologies Kobayashi, Akira Performance of thermal barrier coatings produced by smart plasma processing Вопросы атомной науки и техники |
| description |
Thermal barrier coating typically comprising of bondcoat and yttrium stabilized zirconium topcoat, has been used to improve
the efficiency of turbine engine by providing the capability to sustain significant temperature gradient across the coating.
Alumina and zirconia composite coating was proposed as a potential candidate to improve the qualities of thermal barrier
coating system due to its low melting point and high hardness. The gas tunnel type plasma system, which has high energy
density and also high efficiency, is useful for smart plasma processing. The characteristics of the obtained ceramic coatings
such as Al₂O₃ and ZrO₂ coatings were superior to the conventional ones. The ZrO₂ composite coating has the possibility of the
development of high functionally graded TBC (thermal barrier coating). In this study, the performance such as the mechanical
properties, thermal behavior and high temperature oxidation resistance of the alumina/zirconia functionally graded TBCs
produced by gas tunnel type plasma spraying was investigated and discussed. The results showed that the alumina/zirconia
composite system exhibited the improvement of mechanical properties of thermal barrier coatings and oxidation resistance. |
| format |
Article |
| author |
Kobayashi, Akira |
| author_facet |
Kobayashi, Akira |
| author_sort |
Kobayashi, Akira |
| title |
Performance of thermal barrier coatings produced by smart plasma processing |
| title_short |
Performance of thermal barrier coatings produced by smart plasma processing |
| title_full |
Performance of thermal barrier coatings produced by smart plasma processing |
| title_fullStr |
Performance of thermal barrier coatings produced by smart plasma processing |
| title_full_unstemmed |
Performance of thermal barrier coatings produced by smart plasma processing |
| title_sort |
performance of thermal barrier coatings produced by smart plasma processing |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2006 |
| topic_facet |
Low temperature plasma and plasma technologies |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/82302 |
| citation_txt |
Performance of thermal barrier coatings produced by smart plasma processing / Akira Kobayashi // Вопросы атомной науки и техники. — 2006. — № 6. — С. 181-185. — Бібліогр.: 13 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT kobayashiakira performanceofthermalbarriercoatingsproducedbysmartplasmaprocessing |
| first_indexed |
2025-07-06T08:48:43Z |
| last_indexed |
2025-07-06T08:48:43Z |
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1836886759201308672 |
| fulltext |
LOW TEMPERATURE PLASMA AND PLASMA TECHNOLOGIES
Problems of Atomic Science and Technology. 2006, 6. Series: Plasma Physics (12), p. 181-185 181
PERFORMANCE OF THERMAL BARRIER COATINGS
PRODUCED BY SMART PLASMA PROCESSING
Akira Kobayashi
Joining & Welding Res. Inst. Osaka University,
11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan, e-mail: kobayasi@jwri.osaka-u.ac.jp
Thermal barrier coating typically comprising of bondcoat and yttrium stabilized zirconium topcoat, has been used to improve
the efficiency of turbine engine by providing the capability to sustain significant temperature gradient across the coating.
Alumina and zirconia composite coating was proposed as a potential candidate to improve the qualities of thermal barrier
coating system due to its low melting point and high hardness. The gas tunnel type plasma system, which has high energy
density and also high efficiency, is useful for smart plasma processing. The characteristics of the obtained ceramic coatings
such as Al2O3 and ZrO2 coatings were superior to the conventional ones. The ZrO2 composite coating has the possibility of the
development of high functionally graded TBC (thermal barrier coating). In this study, the performance such as the mechanical
properties, thermal behavior and high temperature oxidation resistance of the alumina/zirconia functionally graded TBCs
produced by gas tunnel type plasma spraying was investigated and discussed. The results showed that the alumina/zirconia
composite system exhibited the improvement of mechanical properties of thermal barrier coatings and oxidation resistance.
PACS: 52.75.Hn; 52.77.-j
1. INTRODUCTION
Zirconia sprayed coatings are widely used as thermal
barrier coatings (TBC) for high temperature protection of
metallic structures in gas turbine hot section components
such as burners, transition ducts, vanes and blades. It allows
the high temperature operation and results to increasing the
efficiency of the engine and the durability of the critical
components. However, their use in diesel engine combustion
chamber components has been quite rare, because of the long
run durability problems in such conditions. The main
problem is the spallation at the interface between the coating
and substrate due to the interface oxidation [1]. Although
zirconia coatings have been used in many applications, the
interface spallation problem is still waiting to be solved
under the critical conditions such as high temperature and
high corrosion environment. For that reason, there have been
many investigations in developing proper TBCs for diesel
engines [2,3].
It is reported that the spallation rate can be reduced but
not completely by using suitable bond coats for the interface
[4]. Nevertheless, it is difficult to find suitable bonding layers
for all kind of substrate material. Alumina and zirconia
composite coating was proposed as a potential candidate to
improve the qualities of thermal barrier coating system due
to its low melting point and high hardness. Also, extremely
high porosity values (up to 25 vol%) of TBC s have been
obtained by functionally graded layer of alumina. TBC
failure occurs easily at the interface between the metallic
bondcoat and topcoat. During high temperature service an
oxide scale consisting mainly of α-alumina forms along
bond/topcoat interface.
The resistance for thermal shock and high temperature
corrosion are important properties in the high
performance TBC. For TBC, the spalling of the coating is
also very important problem as well as the coating quality.
New type plasma spray methods are expected for using
the excellent characteristics of ceramics such as corrosion
resistance, thermal resistance, and wear resistance [5] by
reducing the porosity and increasing the coating density.
The gas tunnel type plasma spraying developed by the
author can make high quality ceramic coatings such as Al2O3
and ZrO2 coating [6] compared to other plasma spraying
method. A high hardness ceramic coating such as Al2O3
coating by the gas tunnel type plasma spraying, were
investigated in the previous study in detail [7-10]. Usually, the
Vickers hardness of this sprayed coating became 20…30%
higher than that of conventional plasma spraying. And, the
porosity was half of the value of the conventional ones.
The Vickers hardness of the zirconia (ZrO2) coating was
increased with decreasing spraying distance, and a higher
Vickers hardness of about Hv = 1200 could be obtained at a
shorter spraying distance of L = 30 mm [11]. This corresponds
to the hardness of sintered ZrO2: Hv = 1,300. ZrO2 coating
formed has a high hardness layer at the surface side, which
shows the graded functionality of hardness [12,13]. With the
increase in the traverse number of plasma spraying, the
hardness distribution was much smoother, corresponding to
the result that the coating became denser.
In this study, composite thermal barrier coatings (TBCs) of
Al2O3+ZrO2 were deposited on SS304 substrates by gas tunnel
type plasma spraying. The performance such as the
mechanical properties, thermal behavior and high temperature
oxidation resistance of the alumina/zirconia functionally
graded TBCs was investigated and discussed. The adhesive
characteristics of such high hardness zirconia-alumina
(ZrO2-Al2O3) composite coatings were also investigated as
well as its mechanical properties.
The resultant coating samples with different Al2O3+ZrO2
mixing ratio and thickness are compared in their corrosion
resistance with Al2O3 percentage and coating thickness as
variables. Corrosion potential and deactivated corrosion
current density are measured and analyzed corresponding to
the microstructure of the coatings.
2. EXPERIMENTALS
2.1. CHARACTERISTICS OF GAS TUNNEL TYPE
PLASMA SPRAYING
Figure 1 shows the gas tunnel type plasma spraying
torch [4,6,7,8,9]. The spraying powder is fed inside
plasma flame in axial direction from center electrode of
plasma gun. So, the spraying powder was molten enough
in the plasma, and the plasma spraying for high melting
point ceramics is available. The coating is formed on the
mailto:kobayasi@jwri.osaka-u.ac.jp
182
Table 2. Chemical composition and size of zirconia and
alumina powder used (20~80% Al2O3 Mixture)
Composition (wt%) Size (µm)
ZrO2 Y2O3 Al2O3 SiO2 Fe2O3
90.78 8.15 0.38 0.20 0.11 10…44
Al2O3 Na2O SiO2 Fe2O3
99.8 0.146 0.01 0.01 10…35
ZrO2
Al2O3
Fig.1. Schematic of the gas tunnel type plasma spraying torch
substrate traversed at the spraying distance: L. In this
case, the gas divertor nozzle diameter was d=20 mm. It
can be easy to produce the high hardness ceramic coatings
by means of the gas tunnel type plasma spraying.
2.2. EXPERIMENTAL PROCEDURE
The gas tunnel type plasma spraying torch used was
shown in Fig. 1. The experimental method to produce the
ceramic coatings by means of the gas tunnel type plasma
spraying is as follows. After igniting plasma gun, the
main vortex plasma jet is produced in the low pressure
gas tunnel. The spraying powder is fed from center inlet
of plasma gun. The coating was formed on the substrate
traversed at the spraying distance of L.
The experimental conditions for the plasma spraying are
shown in Table 1. The power input to the plasma torch was
about P = 25 kW, and the power input to the pilot plasma
torch, which was supplied by the power supply PS-1, was
turned off after starting of the gas tunnel type plasma jet. The
spraying distance was short distance of L = 40 mm.
Table 1. Experimental conditions
Powder: ZrO2+Al2O3 Mixture
Traverse number: N 1~30
Power input, P (kW): 25~28
Working gas flow rate, Q (l/min): 180
Powder feed gas, Q feed (l/min): 10
Spraying distance, L (mm): 40
Traverse speed, v (cm/min): 25~1000
Powder feed rate: w (g/min): 20~35
Gas divertor nozzle dia., d (mm) 20
The working gas was Ar gas, and the flow rate for gas
tunnel type plasma spraying torch was Q = 180 l/min, and
gas flow rate of carrier gas was 10 l/min. The powder feed
rate of zirconia/alumina mixed powder was
w = 20~35 g/min. The traverse speed of the substrate was
changed the value from v=25 to 1000 cm/min. Also the
traverse number was changed 1…30 times. The thickness
of the coating was 50~250 m.
The chemical composition and the particle size of
Zirconia (ZrO2) and/or alumina (Al2O3)powder used in
this study was respectively shown in Table 2. This ZrO2
powder was commercially prepared type of K-90 (PSZ of
8% Y2O3), and Al2O3 powder was the type of K-16T. The
substrate was SUS304 stainless steel (3x50x50), which
was sand-blasted before using.
2.3. ANALYSIS OF COATING PROPERTIES
Micro-structural characterization of thermal sprayed
coatings involves quantitative measurements of geometrical
features such as porosity (in the form of voids, cracks and
other defects) and analysis of material aspects in the coatings
such as splat structure, interfaces, phases, etc. The
microstructure of the cross section of zirconia composite
coating was observed by an optical microscope in this
research. The microscope is equipped with a CCD camera
for image acquisition. Micrographs with two magnifications
(200 X and 400 X) taken on polished cross sections are used
for determining the total porosity and coating thickness by
using image analysis software.
The Vickers hardness Hv50, Hv100 of the sprayed coatings
was measured at the non-pore region in those cross sections
under the condition that the load weight was 50 g, 100 g and
its load time was 15s, 25 s. The Vickers hardness: Hv100 was
calculated as a mean value of 10 point measurements. The
distribution of the Vickers hardness in the cross section of the
coating was measured at each distance from the coating
surface in the thickness direction.
The adhesive strength between the ZrO2 composite
coating and the substrate was measured by using the tension
tester original designed. The test piece for adhesive strength
was 10mm square and the coating surface side and substrate
side was respectively attached to each holder by polymer
type glue. The kgf/cm2 was used as a unit for the adhesive
strength of the composite coating.
The schematic of anodic polarization corrosion system is
shown in Fig. 2, which is a normal potentiostatic polarization
corrosion tester, which is using a Hokuto Denko, HA303
power source. An Ag/AgCl reference electrode (SCE) was
inserted in saturated KCl solution and was connected
galvanically to the test cell by a self-made salt-bridge. A
platinum wire used as the counter electrode was immersed in
the reaction cell containing 500 ml corrosion media of 0.5 M
HCl solution. HCl solution was chosen as corrosion media
because Cl- ions are assumed passing through the coating layer
more easily than another commonly-used anodic oxidant SO4
2-
The sample surfaces were degreased by ultrasonic
process in acetone for 5 minutes then were washed by
Fig.2. Anodic Polarization Corrosion Tester
183
distilled water before putting into test. The cleaned
sample was held by a well-designed sample holder and
immersed in the testing media for 15 min to stabilize its
galvanic contact with the solution, then the sample
potential was set to -0.5V and was swept to +0.5V at a
rate of 10 mV/s. All the tests were carried out at room
temperature.
3. RESULTS AND DISCUSSION
3.1. MICROSTRUCTURE AND VICKERS
HARDNESS OF ZIRCONIA COMPOSITE COATING
Typical optical cross sectional micrographs for
thermal barrier coatings are shown in Fig 3. Those are the
zirconia composite coatings of 20% and 50%Al2O3
mixture. The coatings have a porous and lamellar
structure which is characteristic for this kind of coatings.
The thickness was about 150 µm.
The composition of the microstructure is represented
by gray level variation. It consisted of 2 different layers,
white and gray layers were deposited alternatively. The
analysis by EPMA revealed that white was zirconia
(ZrO2) and gray was alumina (Al2O3). Pores appear to be
dark, which permit them to be distinguished and
quantified by image analysis.
Fig. 4 shows the relationships between Vickers
hardness and porosity of the ZrO2 composite coatings and
the alumina Al2O3 mixing ratio R (wt%), at the same
spraying time. In this case, the coating thickness was
approximately 200 µm at P = 25 kW, L = 40 mm, when
the traverse number was two times.
The average Vickers hardness over the cross section
of zirconia composite coatings is increased with the
increase of the alumina mixing ratio. The increment of
coating hardness corresponds to attendance of alumina
particles with hardness higher than that of zirconia the
Vickers hardness of Al2O3 coating was Hv50 = 1360.
The average porosity over the coating layer shows a
decrease tendency with increasing alumina mixing ratio.
In the meanwhile, the porosity profile (shown in Fig. 6)
over the coating cross-section gives an almost linearly
graded distribution.
3.2. GRADED FUNCTIONALITY OF COMPOSITE
COATING
The hardness distribution of the ZrO2composite
coating has remarkable graded functionality in the case of
large Al2O3 mixing ratio. Because, the part near the
substrate did not change so much, but the Vickers
hardness near the coating surface became much higher.
Figure 5 shows the distribution of Vickers hardness: Hv50
of the zirconia/alumina composite coating shown in Fig. 3
(coating thickness: about 150 m). The distribution of this
composite coating has a highest value in the coating at the
surface side. The maximum hardness was near to
Hv50 = 1300 at the coating surface of l = 40 µm, and
decreased linearly like towards the substrate side.
80% ZrO2-20 % Al2O3
Substrate
50% ZrO2-50 % Al2O3
Substrate
Fig. 3. Micrographs of the cross-section of coating samples
0 20 40 60 80 100
5
10
15
20
25
30
35
1050
1100
1150
1200
1250
1300
1350
1400
Porosity
Binomial fitting
Po
ro
si
ty
p
(%
)
Al
2
O
3
mixing ratio η(%)
Vicker hardness
Binomial fitting
V
ic
ke
r
ha
rd
ne
ss
H
v
Fig.4. Dependence of Vickers hardness of zirconia
composite coating on the alumina mixing rate;
2 times traverse at L=40 mm when P=25 kW
Fig. 5. Distribution of Vickers hardness: Hv50
of the zirconia/alumina composite coating
Vi
ck
er
s
h
ar
dn
es
s,
H
v 5
0
184
20 30 40 50 60 70 80 90
0
500
1000
1500
2000
2500
3000
γ
α
γ
γααα
γ
γ
γ
αα
α
(0
21
0)
α
(3
12
)
α
(2
23
)
α
(2
20
)
α
(1
19
)
α
(1
01
0)
α
(3
00
)
γ
(4
40
)
α
(2
14
)
γ
(5
11
)
α
(1
16
)
α
(0
24
)
δ
(4
02
)
δ
(2
20
)
α
(1
13
)
δ
(3
22
)
α
(1
10
)
θ
(1
11
)
α
(1
04
)
θ
(2
00
)
θ
(2
00
)
θ
(0
04
)α
(0
12
)
As spray
Heat treated at
1050 C-5 hr
In
te
ns
ity
(a
rb
.u
ni
t)
2θ (Degree)
Fig.7. XRD patterns of as sprayed coating and coating after
heat treatment
While, the porosity profile (shown in Fig. 3) over the
coating cross-section gives an almost linearly graded
distribution, increasing from the surface of the coatings
towards the surface of the substrate, as shown in Fig.6. In as-
sprayed condition the porosity variation ranges from 18.95 to
33.23% from the surface of the coatings to the surface of the
substrate. Although lower porosity can increase the average
hardness of the coatings, alumina presence in the coatings is
the origin of the improved hardness because higher mixing
ratio of alumina results in lower porosity.
3.3 OXIDATION OF ZrO2 COMPOSITE COATING
After heat treatment at 1050 ºC for 5 h, the ZrO2
coating system showed spallation from the substrate. But
the Al2O3 coating showed no spallation even failure
occurred after exposure at the same heat treatment
condition. The delamination failure is due to large
thermal stresses developing within the coating and the
phase transformation of Al2O3. Analytical model showed
that plasma sprayed Al2O3 layer should be very thin since
thicker layer would generate larger residual tensile stress.
To evaluate phase transformation of Al2O3 due to
plasma spray process, free standing Al2O3 layer was
oxidized at 1050 ºC for 5 h. X-ray diffraction was
conducted to examine phases of the sprayed layers. A
comparison of diffraction patterns of the as-sprayed and
heat-treated Al2O3 is summarized in Fig.7. The -Al2O3
that was formed during plasma spray undergoes a phase
transformation to a more stable -Al2O3 during heat
treatment, although some fraction of γ phase was retained
in the coating. Other phases, namely δ-, θ- Al2O3 were
also identified. It is noted that the transformation of γ to
had never been direct such that δ and θ phases can be
regarded as the intermediate phases, suggesting that the
transformation of γ to (δ,θ) to occurred in the annealed
coating. The phase transformation of to γ involves a
volume change, resulting in additional residual stresses.
Density values of coated samples believed that an
additional volume change could be attributed to the
porosity closing during heating.
3.4 ANODIC CORROSION POLARIZATION
CHARACTERISTICS OF ZrO2 COMPOSITE
COATING
Figure 8 presents the anodic corrosion polarization
characteristics of the samples coated with different
thickness of 80% ZrO2+ 20%Al2O3 mixture coating. All
the curves are obtained from their first polarization scan.
From the curves, their corrosion potentials increase
clearly with the coating thickness. However, their
corrosion current shows a complicated tendency with the
coating thickness, which is possibly due to the complex
bonding states of the coatings to the substrates because
the effective area of the substrate exposed to the corrosion
media is responsible for the corrosion current.
40 60 80 100 120 140 160 180
18
20
22
24
26
28
30
32
34 80% Zr02-20% Al2O3
Po
ro
si
ty
,p
(%
)
Distance from coating surface ( um)
Porosity
Fig. 4 Porosity distribution over theFig. 6 Porosity dist ribut ion over coat ing
Fig. 6. Porosity distribution over coating cross-section
10-1 100 101 102
-0,6
-0,4
-0,2
0,0
0,2
0,4
Po
te
nt
ia
l E
(A
g/
A
gC
l,
V
)
Current density (µA/mm2)
dash dot: 150µm
Solid: 235µm
Dash: 305µm
ZrO
2
80%+Al
2
O
3
20%
Fig.8 Corrosion curve of coatings with different
thickness
50 100 150 200 250 300 350
-0,45
-0,44
-0,43
-0,42
-0,41
-0,40
-0,39
-0,38
-0,37
-0,36
-0,35
100B ZrO2
50% Al2O3 + 50% ZrO2
100B Al2O3
C
or
ro
si
on
P
ot
en
tia
l (
A
g/
A
gC
l,
V
)
Coating thickness (um)
Fig.9. Corrosion potential versus thickness and composite
185
Figure 9 displays the relationships of the corrosion
potential of the tested samples to the alumina mixing ratios
and thickness. As expected, the trends show that the
corrosion potential goes up slightly with both the alumina
content ratio and coating thickness. Theoretically, high
corrosion potential means lower electrochemical activity and
higher oxidation resistance. So, in conclusion, higher
thickness and lower porosity sprayed coatings lead to
increase of corrosion resistance because both higher
thickness and lower porosity provide stronger diffusion
resistance to prevent the anodic oxidants of the corrosion
solution from accessing the interface of the coated samples.
CONCLUSIONS
The performance such as the mechanical properties,
thermal behavior and high temperature oxidation
resistance of the ZrO2/Al2O3 composite coating produced
by gas tunnel type plasma spraying was investigated, and
the following results were obtained.
1)The ZrO2 Al2O3 composite coating has graded
functionality on the hardness and the porosity, and has a
possibility of the development of high functionally
graded TBC (thermal barrier coating).
2)The effect of alumina mixing on the Vickers hardness
of the ZrO2 composite coating was also clarified in
order to develop high functionally graded TBC.
3) The ZrO2 composite system exhibited the improvement
of mechanical properties of thermal barrier coatings and
oxidation resistance.
4)The -Al2O3 that was formed during plasma spraying
undergoes a phase transformation to a more stable -
Al2O3 during heat treatment, although some fraction of
γ phase was retained in the coating. The high
temperature oxidation behavior of the functionally
graded TBCs showed the effectiveness of Al2O3 layer
functioning as an oxidation barrier.
5)The higher alumina content and thicker coatings, the
better the corrosion resistance, which is attributed to the
diffusion resistance of the coating layers to corrosion
reaction.
REFERENCES
1. R. Vassen, G. Kerkhoff, and D. Stoever, Development of a
micromechanical life prediction model for plasma sprayed
thermal barrier coatings // Mater. Sci. Eng. 2001, A303,
p. 100-109.
2. D.N. Assanis // Journal of Materials Processing Technology.
1989, v. 4, p. 232.
3. T. M. Yonushonis // Journal of Thermal Spray Technology.
1997, v.6, N 1, p. 50.
4. P. Ramaswamy, S. Seetharamu, K.B.R.Varma, and K.J. Rao.
Thermal shock charateristics of plasma sprayed mullite
coatings// J. Therm. Spray Technol. 1998, v. 7, N 4, p. 497-
504.
5. T. Araya // J. Weld. Soc. Jpn. 1988, v. 57-4, p. 216-222.
6. Y. Arata, A. Kobayashi, Y. Habara and S. Jing. Gas Tunnel
Type Plasma Spraying // Trans. of JWRI. 1986, v. 15-2,
p. 227-231.
7. Y. Arata, A. Kobayashi, and Y. Habara // J. Applied Physics.
1987, v. 62, p. 4884-4889.
8. Y. Arata, A. Kobayashi and Y. Habara. Formation of Alumina
Coatings by Gas Tunnel Type Plasma Spraying (in Japanese) //
J. High Temp. Soc. 1987, v. 13, p. 116-124.
9. A. Kobayashi, S. Kurihara, Y. Habara, and Y. Arata // J. Weld.
Soc. Jpn. 1990, v. 8, p. 457-463.
10. A. Kobayashi. Property of an Alumina Coating Sprayed
with a Gas Tunnel Plasma Spraying // Proc. of ITSC. 1992,
p. 57-62.
11. A. Kobayashi. Formation of High Hardness Zirconia
Coatings by Gas Tunnel Type Plasma Spraying // Surface and
Coating Technology. 1990, v. 90, p. 197-202.
12. A. Kobayashi and T. Kitamura. High Hardness Zirconia
Coating by Means of Gas Tunnel Type Plasma Spraying // J. of
IAPS. 1997, v. 5, p. 62-68 (in Japanese).
13. A. Kobayashi, T. Kitamura // VACUUM. 2000, v. 59-1,
p. 194-202.
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