- Email: [email protected]
Estimation of spallation life of thermal barrier coating of gas turbine blade by thermal fatigue test
Surface & Coatings Technology 205 (2011) S157–S160
Contents lists available at ScienceDirect
Surface & Coatings Technology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / s u r f c o a t
Estimation of spallation life of thermal barrier coating of gas turbine blade by thermal fatigue test In-Hwan Shin a, Jae-Mean Koo a, Chang-Sung Seok a,⁎, Sung-Ho Yang b, Tack-Woon Lee b, Bum-Soo Kim c a b c
Department of Mechanical Engineering, Sungkyunkwan University, Suwon, 440–746, Republic of Korea Technology Team, KPS Gas Turbine Technology Service Center, Incheon, 404–170, Republic of Korea Korea Electric Power Research Institute, Daejeon, 305–380, Republic of Korea
a r t i c l e
i n f o
Available online 5 March 2011 Keywords: Thermal barrier coating (TBC) Thermally grown oxide (TGO) Thermal fatigue Delamination life Delaminated area
a b s t r a c t Plasma-sprayed thermal barrier coatings (TBCs) are applied to protect the blades of a gas turbine system from high-temperature gas and to lower the surface temperature of the blades. The failure of TBC is directly connected to the failure of the blades because the spallation of a ceramic layer leads to the acceleration of local corrosion and oxidation at the location of failure. Therefore, the spallation life of TBC is very important in the evaluation of the reliability of a gas-turbine blade. In this study, thermal fatigue tests were performed at 1100 °C and 1151 °C. Then, c-scanning and bond strength tests were performed for TBC specimens that were thermally aged by thermal fatigue tests. From the results, an empirical equation based on the ratio of the delamination area and the thermal cycle number was presented and the spallation life of a TBC specimen could be roughly estimated using the relationship between the delaminated area and the number of cycles. © 2011 Elsevier B.V. All rights reserved.
1. Introduction
2. Thermal fatigue test
Thermal barrier coatings (TBCs) are applied to protect the components of aircraft engines and gas turbines from high temperatures and to lower the surface temperature of specific turbine components [1,2]. TBCs usually consist of a MCrAlY (where M=Ni, Co or both) bond coat, a ceramic (7–8 wt.% ZrO2–Y2O3) top coat, and a thermally grown oxide (TGO). Among them, the TGO is formed at the interface between the top coat and the bond coat during the operation of the gas turbine, and the possibility of failure at the interface increases due to the various stresses and TGO layer [3,6]. Generally, the TBC applied to an aircraft engine and gas turbine blade is exposed to thermal fatigue, which severely influences coating failure [4,5]. In this study, thermal fatigue tests for coin-shaped TBC specimens were performed at 1100 °C and 1151 °C. Then, c-scanning and bond strength tests were performed for TBC specimens that were thermally aged by thermal fatigue tests. From the test results, the coating failure life and the failure mechanism were evaluated. Subsequently, a prediction method of the coating failure life by thermal fatigue was suggested.
2.1. Materials and specimens
⁎ Corresponding author. Tel.: +82 31 290 7446; fax: +82 31 290 7482. E-mail address: [email protected] (C.-S. Seok). 0257-8972/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2011.02.068
Fig. 1 shows the schematic illustration of a coin-shaped coating specimen with a diameter of 25 mm. The substrate of specimen was a Ni-base superalloy (GTD111DS) and the MCrAlY bond coat was deposited onto the Ni-base superalloy by LVPS (Low Vacuum Plasma Spray). The YSZ (Yttria Stabilized Zirconia) top coat was deposited onto the MCrAlY bond coat by APS (Air Plasma Spray) in the form of a DVC structured layer as described in Table 1.
2.2. Test method and results Thermal fatigue tests for evaluating the spallation life of TBC specimen were performed at two different temperature conditions. One cycle of a thermal fatigue test consisted of two steps. In the first step, a specimen was heated for 45 min in a furnace at 1100 °C and 1151 °C. In the second step, a specimen was cooled for 15 min at room temperature [7]. The spallation of TBC was observed with the naked eye when specimens were cooled at room temperature. In all the cases of the thermal fatigue tests, crack initiation occurred at the edges of the specimen before the spallation of an entire top coat occurred. Schlichting et al. [8] defined the life of the delamination area of 50% as the spallation life of TBC during the thermal fatigue test. In this study, since it is difficult to measure the delamination area of TBC
S158
I.-H. Shin et al. / Surface & Coatings Technology 205 (2011) S157–S160
Fig. 2. Results of C-scanning analyses investigating the delaminated area in the specimen.
4. Bond strength test
Fig. 1. Schematic illustration of a coating specimen [7].
during the thermal fatigue test, we defined the life of the whole delamination area of TBC as the spallation life of TBC. From the results, spallation lives of TBC specimens were evaluated from 10 to 19 at 1151 °C and from 37 to 52 at 1100 °C.
3. C-scanning analysis To estimate the failure mechanism of TBC, we prepared the specimens that were intentionally stopped after 1, 2, 5, and 10 cycles of thermal fatigue tests. At all those samples, c-scanning analysis was performed afterwards. The delaminated area of TBC in the specimen was detected using the reversed phase of the ultra-sonic signals. By c-scanning, the delamination of TBC in the specimen could be detected after 10 cycles of the thermal fatigue tests. Fig. 2 shows the results of c-scanning for the delamination of TBC in the specimen after 1, 2, 5, 10 and 20 cycles of thermal fatigue tests at 1100 °C. To verify the reliability of the c-scanning analysis method, micro-structural analyses were performed by SEM. In case of the as-sprayed coating specimen without the degradation in Fig. 3, it was confirmed that no crack exists internally. Fig. 4 shows SEM micrographs of the crosssection of a TBC specimen for 20 cycles, respectively. From these results, it was verified that the crack by delamination occurs at the edge and propagates toward the center, results which were also obtained by Schlichting et al. [8] and Stover et al. [10]. Kim et al. reported that tensile stress occurs in the direction perpendicular to the propagation path of the edge crack and the tensile stress at the edge remains constant during steady state and then instantaneously increases during the cooling step [7]. In addition, Quadakkers, et al. reported that TGO is formed at the interface between the top coat and the bond coat during the operation of the gas turbine, and the possibility of failure at the interface increases due to the various stresses and TGO layers [3]. It has been known that normal stress by oxidation influences the delamination of coating in the edge of a specimen. In this study, we observed the growth of the thickness of TGO from one cycle to 20 cycles at 1100 °C (Fig. 5). The crack propagated according to an increase of cycle number and it was estimated that the crack growth resulted from the TGO formation by high temperature degradation and the high normal stress at the edge.
Kim et al. reported delamination had already occurred at the edge of the specimen before the specimens were pulled apart by force and as the number of cycle increased, the bond strength gradually decreased according to an increase of delamination area, as shown in Fig. 6 [7]. From this, it was estimated that the delamination area is related to the bond strength and we could find the relationship between the delamination area and the thermal failure life. In order to obtain this relationship, additional bond strength tests were performed with TBC specimens damaged by thermal fatigue at 1150 °C. The damaged specimen bonded to the jig fixtures by epoxy adhesive was placed in the oven for 2 h at 170 °C to ensure curing of the epoxy (Type 2214). The curing time was obtained by the repetitive bond strength tests until achieving sufficient adhesion force. Bond strength tests were conducted with a test speed of 1 mm/ min according to ASTM C633-79 under tensile loading and the relationship between the delamination area and the thermal fatigue cycle was analyzed. The delaminated area after completion of the bond strength tests was measured through image analyses. As shown in Fig. 7, the ratio of the delaminated area through the thermal fatigue tests increased from 21% to 55% after 5 cycles at 1151 °C and from 15% to 54% after 10 cycles at 1100 °C. Since the spallation life of TBC is equal to the number of cycles whereby the delaminated area is the total surface area, the spallation life of TBC was calculated at 19 cycles from curve fitting under 1151 °C and 35 cycles under 1100 °C. The curve fitting equations are as follows; Ad = 23N
0:5
at 1151 ˚C;
ð1Þ
Ad = 17N
0:5
at 1100 ˚C;
ð2Þ
Table 1 Specifications of each layer of the coated specimen [5,7]. Component
Material
Coating type
Thickness
Top coat Bond coat
YSZ (7–8% ZrO2–Y2O3) MCrAlY (Co 32Ni 21Cr 8Al 0.5Y) GTD-111DS
APS LVPS
470 μm 250 μm
–
3 mm
Substrate
Fig. 3. SEM micrograph showing the cross-section of an as-sprayed coating specimen.
I.-H. Shin et al. / Surface & Coatings Technology 205 (2011) S157–S160
S159
Fig. 4. SEM micrographs showing the cross-section of a coating specimen after 20 cycles (a) left edge, (b and c) middle, and (d) right edge.
and temperature, the following empirical equation including two variables was obtained by the regression analysis method.
Ad =
ðTo −960Þ 0:5 N ; 8:3
ð3Þ
where To is the test temperature. From Eq. (3), spallation lives were calculated at 26 cycles under 1121 °C and 83 cycles under 1050 °C, as shown in Fig. 8. To evaluate the cycles calculated under 1121 °C and 1050 °C, thermal fatigue tests were performed at those temperature conditions until the spallation of TBC occurred. Then, spallation lives of TBC obtained from the thermal fatigue tests were compared with those of TBC calculated using Eq. (3) as shown in Fig. 8. The results indicate that the spallation life of TBC could be roughly estimated using the relationship between the delaminated area and cycle number of thermal fatigue. 5. Conclusions and summary Fig. 5. Micrographs showing the thickness of TGO at 20 cycles of thermal fatigue test.
In this study, thermal fatigue tests were performed for coinshaped TBC specimens used for the first-stage blade of a gas turbine. Through c-scanning and bond strength tests for thermal cyclicallyaged TBC specimens, the following conclusions were made on spallation lives of coin-shaped TBC samples with coating layers:
where Ad is the ratio of delamination area and N is the thermal cycle number. As a result of the comparison between the curves, it can be seen that the spallation life of the TBC specimen by thermal fatigue test agrees with that by the curve fitting. From these equations, it can be seen that the delamination area is proportional to the square root of the cycle number. Also, it has been known that the temperature accelerating the oxidation of the bond coating according to the thermal fatigue is over 950 °C [9]. In this study, with reference to this, since the delamination area is the function of the thermal fatigue cycle
1) During thermal fatigue tests for coin-type specimens, delamination cracks occurred at the edge of a specimen first and then the area of the edge delamination gradually increased toward the center as the number of cycles increased until the entire spallation of the top coat by c-scanning and SEM. 2) We observed the growth of thickness of TGO from one cycle to 20 cycles at 1100 °C. Also, the crack propagated according to an increase of cycle number. It was estimated that the crack growth
Fig. 6. Results of bond strength tests in case of thermal fatigue [7].
Fig. 7. Spallation life of TBC at 1121 °C and 1050 °C predicted by the interpolation method.
S160
I.-H. Shin et al. / Surface & Coatings Technology 205 (2011) S157–S160
equation, the spallation life of a TBC specimen could be roughly estimated using the relationship between the delaminated area and cycle number of thermal fatigue.
Acknowledgments The authors are grateful for the support provided by the Brain Korea 21 Project and R&D (R-2005-1-389) which is funded by MKE (Ministry of Knowledge Economy, Republic of Korea).
References
Fig. 8. Results predicted the spallation life of TBC is compared to results of the thermal fatigue tests.
resulted from the TGO formation by high temperature degradation and the high normal stress at the edge. 3) In this study, an empirical equation on the ratio of delamination area and the thermal cycle number was presented. By using this
[1] K. Vaidyanathan, E.H. Jordan, M. Gell, Acta Mater. 52 (2004) 1107. [2] J.A. Thompson, T.W. Clyne, Acta Mater. 49 (2001) 1565. [3] W.J. Quadakkers, V. Shemet, D. Sebold, R. Anton, E. Wessel, L. Singheiser, Surf. Coat Tech 199 (2005) 77. [4] Mats Eskner, Doctoral Thesis, 2004. [5] N. P. Padture, M. Gell, E. H. Jordan, Vol. 296, pp. 280–284, 2002. [6] M. Madhwal, Eric H. Jordan, Gell Maurice, Materilas Sci. Eng. A 384 (2004) 151. [7] Kim Dae-Jin, Shin In-Hwan, Koo Jae-Mean, Seok Chang-Sung, Lee Tack-Woon, Surf. Coat. Tech 205 (2010) 451. [8] K.W. Schlichting, N.P. Padture, E.H. Jordan, M. Gell, Mater. Sci. Eng. A 342 (2003) 120. [9] Brodin Hakan, Eskner Mats, Surf. Coat. Tech 187 (2004) 113. [10] D. Stöver, G. Pracht, H. Lehmann, M. Dietrich, J.E. Döring, R. Vaβen, J. Therm. Spray Technol. 13 (1) (2004) 76.
Contents lists available at ScienceDirect
Surface & Coatings Technology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / s u r f c o a t
Estimation of spallation life of thermal barrier coating of gas turbine blade by thermal fatigue test In-Hwan Shin a, Jae-Mean Koo a, Chang-Sung Seok a,⁎, Sung-Ho Yang b, Tack-Woon Lee b, Bum-Soo Kim c a b c
Department of Mechanical Engineering, Sungkyunkwan University, Suwon, 440–746, Republic of Korea Technology Team, KPS Gas Turbine Technology Service Center, Incheon, 404–170, Republic of Korea Korea Electric Power Research Institute, Daejeon, 305–380, Republic of Korea
a r t i c l e
i n f o
Available online 5 March 2011 Keywords: Thermal barrier coating (TBC) Thermally grown oxide (TGO) Thermal fatigue Delamination life Delaminated area
a b s t r a c t Plasma-sprayed thermal barrier coatings (TBCs) are applied to protect the blades of a gas turbine system from high-temperature gas and to lower the surface temperature of the blades. The failure of TBC is directly connected to the failure of the blades because the spallation of a ceramic layer leads to the acceleration of local corrosion and oxidation at the location of failure. Therefore, the spallation life of TBC is very important in the evaluation of the reliability of a gas-turbine blade. In this study, thermal fatigue tests were performed at 1100 °C and 1151 °C. Then, c-scanning and bond strength tests were performed for TBC specimens that were thermally aged by thermal fatigue tests. From the results, an empirical equation based on the ratio of the delamination area and the thermal cycle number was presented and the spallation life of a TBC specimen could be roughly estimated using the relationship between the delaminated area and the number of cycles. © 2011 Elsevier B.V. All rights reserved.
1. Introduction
2. Thermal fatigue test
Thermal barrier coatings (TBCs) are applied to protect the components of aircraft engines and gas turbines from high temperatures and to lower the surface temperature of specific turbine components [1,2]. TBCs usually consist of a MCrAlY (where M=Ni, Co or both) bond coat, a ceramic (7–8 wt.% ZrO2–Y2O3) top coat, and a thermally grown oxide (TGO). Among them, the TGO is formed at the interface between the top coat and the bond coat during the operation of the gas turbine, and the possibility of failure at the interface increases due to the various stresses and TGO layer [3,6]. Generally, the TBC applied to an aircraft engine and gas turbine blade is exposed to thermal fatigue, which severely influences coating failure [4,5]. In this study, thermal fatigue tests for coin-shaped TBC specimens were performed at 1100 °C and 1151 °C. Then, c-scanning and bond strength tests were performed for TBC specimens that were thermally aged by thermal fatigue tests. From the test results, the coating failure life and the failure mechanism were evaluated. Subsequently, a prediction method of the coating failure life by thermal fatigue was suggested.
2.1. Materials and specimens
⁎ Corresponding author. Tel.: +82 31 290 7446; fax: +82 31 290 7482. E-mail address: [email protected] (C.-S. Seok). 0257-8972/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2011.02.068
Fig. 1 shows the schematic illustration of a coin-shaped coating specimen with a diameter of 25 mm. The substrate of specimen was a Ni-base superalloy (GTD111DS) and the MCrAlY bond coat was deposited onto the Ni-base superalloy by LVPS (Low Vacuum Plasma Spray). The YSZ (Yttria Stabilized Zirconia) top coat was deposited onto the MCrAlY bond coat by APS (Air Plasma Spray) in the form of a DVC structured layer as described in Table 1.
2.2. Test method and results Thermal fatigue tests for evaluating the spallation life of TBC specimen were performed at two different temperature conditions. One cycle of a thermal fatigue test consisted of two steps. In the first step, a specimen was heated for 45 min in a furnace at 1100 °C and 1151 °C. In the second step, a specimen was cooled for 15 min at room temperature [7]. The spallation of TBC was observed with the naked eye when specimens were cooled at room temperature. In all the cases of the thermal fatigue tests, crack initiation occurred at the edges of the specimen before the spallation of an entire top coat occurred. Schlichting et al. [8] defined the life of the delamination area of 50% as the spallation life of TBC during the thermal fatigue test. In this study, since it is difficult to measure the delamination area of TBC
S158
I.-H. Shin et al. / Surface & Coatings Technology 205 (2011) S157–S160
Fig. 2. Results of C-scanning analyses investigating the delaminated area in the specimen.
4. Bond strength test
Fig. 1. Schematic illustration of a coating specimen [7].
during the thermal fatigue test, we defined the life of the whole delamination area of TBC as the spallation life of TBC. From the results, spallation lives of TBC specimens were evaluated from 10 to 19 at 1151 °C and from 37 to 52 at 1100 °C.
3. C-scanning analysis To estimate the failure mechanism of TBC, we prepared the specimens that were intentionally stopped after 1, 2, 5, and 10 cycles of thermal fatigue tests. At all those samples, c-scanning analysis was performed afterwards. The delaminated area of TBC in the specimen was detected using the reversed phase of the ultra-sonic signals. By c-scanning, the delamination of TBC in the specimen could be detected after 10 cycles of the thermal fatigue tests. Fig. 2 shows the results of c-scanning for the delamination of TBC in the specimen after 1, 2, 5, 10 and 20 cycles of thermal fatigue tests at 1100 °C. To verify the reliability of the c-scanning analysis method, micro-structural analyses were performed by SEM. In case of the as-sprayed coating specimen without the degradation in Fig. 3, it was confirmed that no crack exists internally. Fig. 4 shows SEM micrographs of the crosssection of a TBC specimen for 20 cycles, respectively. From these results, it was verified that the crack by delamination occurs at the edge and propagates toward the center, results which were also obtained by Schlichting et al. [8] and Stover et al. [10]. Kim et al. reported that tensile stress occurs in the direction perpendicular to the propagation path of the edge crack and the tensile stress at the edge remains constant during steady state and then instantaneously increases during the cooling step [7]. In addition, Quadakkers, et al. reported that TGO is formed at the interface between the top coat and the bond coat during the operation of the gas turbine, and the possibility of failure at the interface increases due to the various stresses and TGO layers [3]. It has been known that normal stress by oxidation influences the delamination of coating in the edge of a specimen. In this study, we observed the growth of the thickness of TGO from one cycle to 20 cycles at 1100 °C (Fig. 5). The crack propagated according to an increase of cycle number and it was estimated that the crack growth resulted from the TGO formation by high temperature degradation and the high normal stress at the edge.
Kim et al. reported delamination had already occurred at the edge of the specimen before the specimens were pulled apart by force and as the number of cycle increased, the bond strength gradually decreased according to an increase of delamination area, as shown in Fig. 6 [7]. From this, it was estimated that the delamination area is related to the bond strength and we could find the relationship between the delamination area and the thermal failure life. In order to obtain this relationship, additional bond strength tests were performed with TBC specimens damaged by thermal fatigue at 1150 °C. The damaged specimen bonded to the jig fixtures by epoxy adhesive was placed in the oven for 2 h at 170 °C to ensure curing of the epoxy (Type 2214). The curing time was obtained by the repetitive bond strength tests until achieving sufficient adhesion force. Bond strength tests were conducted with a test speed of 1 mm/ min according to ASTM C633-79 under tensile loading and the relationship between the delamination area and the thermal fatigue cycle was analyzed. The delaminated area after completion of the bond strength tests was measured through image analyses. As shown in Fig. 7, the ratio of the delaminated area through the thermal fatigue tests increased from 21% to 55% after 5 cycles at 1151 °C and from 15% to 54% after 10 cycles at 1100 °C. Since the spallation life of TBC is equal to the number of cycles whereby the delaminated area is the total surface area, the spallation life of TBC was calculated at 19 cycles from curve fitting under 1151 °C and 35 cycles under 1100 °C. The curve fitting equations are as follows; Ad = 23N
0:5
at 1151 ˚C;
ð1Þ
Ad = 17N
0:5
at 1100 ˚C;
ð2Þ
Table 1 Specifications of each layer of the coated specimen [5,7]. Component
Material
Coating type
Thickness
Top coat Bond coat
YSZ (7–8% ZrO2–Y2O3) MCrAlY (Co 32Ni 21Cr 8Al 0.5Y) GTD-111DS
APS LVPS
470 μm 250 μm
–
3 mm
Substrate
Fig. 3. SEM micrograph showing the cross-section of an as-sprayed coating specimen.
I.-H. Shin et al. / Surface & Coatings Technology 205 (2011) S157–S160
S159
Fig. 4. SEM micrographs showing the cross-section of a coating specimen after 20 cycles (a) left edge, (b and c) middle, and (d) right edge.
and temperature, the following empirical equation including two variables was obtained by the regression analysis method.
Ad =
ðTo −960Þ 0:5 N ; 8:3
ð3Þ
where To is the test temperature. From Eq. (3), spallation lives were calculated at 26 cycles under 1121 °C and 83 cycles under 1050 °C, as shown in Fig. 8. To evaluate the cycles calculated under 1121 °C and 1050 °C, thermal fatigue tests were performed at those temperature conditions until the spallation of TBC occurred. Then, spallation lives of TBC obtained from the thermal fatigue tests were compared with those of TBC calculated using Eq. (3) as shown in Fig. 8. The results indicate that the spallation life of TBC could be roughly estimated using the relationship between the delaminated area and cycle number of thermal fatigue. 5. Conclusions and summary Fig. 5. Micrographs showing the thickness of TGO at 20 cycles of thermal fatigue test.
In this study, thermal fatigue tests were performed for coinshaped TBC specimens used for the first-stage blade of a gas turbine. Through c-scanning and bond strength tests for thermal cyclicallyaged TBC specimens, the following conclusions were made on spallation lives of coin-shaped TBC samples with coating layers:
where Ad is the ratio of delamination area and N is the thermal cycle number. As a result of the comparison between the curves, it can be seen that the spallation life of the TBC specimen by thermal fatigue test agrees with that by the curve fitting. From these equations, it can be seen that the delamination area is proportional to the square root of the cycle number. Also, it has been known that the temperature accelerating the oxidation of the bond coating according to the thermal fatigue is over 950 °C [9]. In this study, with reference to this, since the delamination area is the function of the thermal fatigue cycle
1) During thermal fatigue tests for coin-type specimens, delamination cracks occurred at the edge of a specimen first and then the area of the edge delamination gradually increased toward the center as the number of cycles increased until the entire spallation of the top coat by c-scanning and SEM. 2) We observed the growth of thickness of TGO from one cycle to 20 cycles at 1100 °C. Also, the crack propagated according to an increase of cycle number. It was estimated that the crack growth
Fig. 6. Results of bond strength tests in case of thermal fatigue [7].
Fig. 7. Spallation life of TBC at 1121 °C and 1050 °C predicted by the interpolation method.
S160
I.-H. Shin et al. / Surface & Coatings Technology 205 (2011) S157–S160
equation, the spallation life of a TBC specimen could be roughly estimated using the relationship between the delaminated area and cycle number of thermal fatigue.
Acknowledgments The authors are grateful for the support provided by the Brain Korea 21 Project and R&D (R-2005-1-389) which is funded by MKE (Ministry of Knowledge Economy, Republic of Korea).
References
Fig. 8. Results predicted the spallation life of TBC is compared to results of the thermal fatigue tests.
resulted from the TGO formation by high temperature degradation and the high normal stress at the edge. 3) In this study, an empirical equation on the ratio of delamination area and the thermal cycle number was presented. By using this
[1] K. Vaidyanathan, E.H. Jordan, M. Gell, Acta Mater. 52 (2004) 1107. [2] J.A. Thompson, T.W. Clyne, Acta Mater. 49 (2001) 1565. [3] W.J. Quadakkers, V. Shemet, D. Sebold, R. Anton, E. Wessel, L. Singheiser, Surf. Coat Tech 199 (2005) 77. [4] Mats Eskner, Doctoral Thesis, 2004. [5] N. P. Padture, M. Gell, E. H. Jordan, Vol. 296, pp. 280–284, 2002. [6] M. Madhwal, Eric H. Jordan, Gell Maurice, Materilas Sci. Eng. A 384 (2004) 151. [7] Kim Dae-Jin, Shin In-Hwan, Koo Jae-Mean, Seok Chang-Sung, Lee Tack-Woon, Surf. Coat. Tech 205 (2010) 451. [8] K.W. Schlichting, N.P. Padture, E.H. Jordan, M. Gell, Mater. Sci. Eng. A 342 (2003) 120. [9] Brodin Hakan, Eskner Mats, Surf. Coat. Tech 187 (2004) 113. [10] D. Stöver, G. Pracht, H. Lehmann, M. Dietrich, J.E. Döring, R. Vaβen, J. Therm. Spray Technol. 13 (1) (2004) 76.