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Effect of ion implantation on growth of thermally grown oxide in MCrAlY coating for TBC
Surface & Coatings Technology 205 (2010) S435–S438
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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
Effect of ion implantation on growth of thermally grown oxide in MCrAlY coating for TBC Eungsun Byon ⁎, Shihong Zhang 1, Sung-Hun Lee, Goo-Hyun Lee, Sik-Chol Kwon Material Processing Research Department, Korea Institute of Materials Science (KIMS), 66 Sangnam-dong, Changwon, Kyungnam, 641-010, Republic of Korea
a r t i c l e
i n f o
Available online 26 September 2010 Keywords: Plasma source ion implantation Thermally grown oxide Thermal barrier coating Oxidation
a b s t r a c t Thermal barrier coatings (TBCs) have been widely used in various gas turbines for aircraft propulsion and power generation. TBCs consist of a metal bond coat and a ceramic top coat of YSZ. It is generally known that the TBC′ life strongly depends on the thermally grown oxide (TGO) because failure of TBCs occurs when the TGO reached a critical thickness. In this study, ion implantation of novel elements has been made on the bond coat which acts as an oxidation barrier for suppressing the TGO growth. The effects of type of ion implanted elements on the TGO formation were investigated. The oxidized specimens at 1150 °C were characterized by SEM, XRD, RBS and AES. From the results, CoNiCrAlY bond coat with an oxidation barrier was found to be effective in suppressing growth of the TGO. © 2010 Elsevier B.V. All rights reserved.
1. Introduction The demand for improved performance in high-temperature mechanical systems has led to increasingly harsh operating environments, particularly for the components in advanced gas-turbine engines. Future improvements in gas-turbine performance will require even higher operating efficiencies, longer operating lifetimes, and reduced emissions. Achieving these requirements will necessitate still further increases in the gas inlet temperatures [1]. Thermal barrier coatings (TBCs) have been widely used in various gas turbines for aircraft propulsion and power generation. TBCs consist of a MCrAlY bond coat and a ceramic top coat of YSZ. Using this approach, temperature drop of up to 170 °C at the metal surface has been estimated, enabling the operation of gas-turbine engines at higher gas inlet temperatures [2]. It is generally known that the TBC′ life strongly depends on the thermally grown oxide (TGO) formed between bond coat and YSZ coating during service of high-temperature because spallation and/or cracking of the thickening TGO scale is the ultimate failure mechanism of commercial TBCs. [3] With increasing TGO thickness, cracks propagate by interface separation, buckling and kinking. Once the TGO spalls, it will spall together with the TBC, leaving the system with no temperature barrier protection. Many attempts have been made to suppress the TGO growth in the bond coat by third element addition such as Pt, Pd, Rh, Ir and Ru etc., preoxidation at a low pressure of oxygen environment [4]. Third element ⁎ Corresponding author. E-mail address: [email protected] (E. Byon). 1 Current address: School of Materials Science and Engineering, Anhui University of Technology, Maanshan, Anhui province 243002, China. 0257-8972/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2010.08.134
addition tends to reduce mechanical properties at a high-temperature, and it is the non-cost-effective process. Depletions of Al in the bond coat during the pre-oxidation may result in growing of spinel type oxide, which are believed to prompt the spalling of TBCs. The diffusion barrier is one of the promising technologies to retard TGO growth by isolation bond coat from oxygen from hot gas. Oxygen is essential to form the oxide of metal elements. Moreever, the coating has interfaces between bond coat and YSZ top coat. Therefore, interface failure will be another issue. In this study, ion implantation of novel elements has been made on the bond coat which acts as an oxidation barrier for suppressing the TGO growth. 2. Experimental Disc type of dimensions 25 mm × 5 mm was prepared as a substrate. The CoNiCrAlY bond coat was produced by the vacuum plasma spray (VPS) on a Ni-base alloy substrate (IN718). Prior to deposit, the substrate surface was blasted with Al2O3 grits and cleaned by transferred arc. After evacuation, the VPS spray chamber is filled with N2 gas and maintained at 60 mbar of low pressure during spraying to allow coatings of reactive metals to be produced without oxidation. Plasma spraying of bond coat was conducted on the substrate by a GTV F6 vacuum plasma spray system. Two types of ion species, Nb and N, were implanted on CoNiCrAlY bond coat using plasma source ion implantation (PSII) equipped with filtered vacuum arc source. Details of the processing can be found elsewhere [5,6]. Highly ionized Mg plasmas were generated from the filtered vacuum arc source. Then the Nb-ions were accelerated within the electric field between a sheath and substrates. The electric energy of the implantation field was 27.5 keV. For the nitrogen-ion
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E. Byon et al. / Surface & Coatings Technology 205 (2010) S435–S438
AES and RBS analysis were conducted to determine elements depth profile and doses in the nitrogen and Nb-ion implanted layer. AES depth profiles of the Nb- and Nb/N-ion implanted specimens are shown in Fig. 1. From the figure, an elemental trace for Nb and N varies gradually from the surface to the bulk without forming a distinct interface. This is one of the advantages of PSII as compared to coating process. A maximum implantation depth of Nb-ions is formed after 7 and 4 min of sputtering as shown in Fig. 1(a) and (b), respectively, indicating that Nb has been successfully implanted into the bond coat. However the amount of implanted ions of Nb in Fig. 1(a) is much larger than in Fig. 1(b). It may be caused by enhanced plasma density vicinity of the samples by additional nitrogen plasma.
RBS spectra and calculated data of the same sample as Fig. 1 are shown in Fig. 2. The Nb-ion dose is 6.28 × 1016 ions/cm2 in the sample (a). In the case of Nb and N implantation, there are pronounced Nb and N implantation. The retained ion doses of Nb and N are 5.22 × 1016 ions/cm2 and 1.69 × 1016 ions/cm2, respectively. From the RBS simulation, implanted ions seem to form compounds like nonstoichiometric NbO and NbNO for Nb-ion implanted sample and Nb and N-ions implanted one, respectively. The XRD-patterns of the as-sprayed coating with and without ion implantation are shown in Fig. 3. The XRD peaks of bond coat without implantation shows signals of the γ + β phase mainly. The Nb and Nb/ N-ion implanted coatings have similar phase compositions like in the as-sprayed one. Comparing to as-sprayed one, however, the peaks of ion implanted ones were broadened, which indicates less crystalline nature are involved. Fig. 4 shows XRD-patterns of the CoNiCrAlY bond coating with and without ion implantation after isothermal oxidation for (a) 50 h and (b) 100 h. Exposing as-sprayed and Nb, Nb/N-ion implanted specimens at 1150 °C in the air for 50 h, and 100 h, lead to significant differences in the oxidized components and thickness. After 50h oxidation, XRD-patterns of as-sprayed coating shows signal of αalumina and spinel oxide. By Nb and N-ion implantation, amounts of α-alumina and spinel oxide are reduced significantly. With increasing
Fig. 1. AES depth profiles of ion implanted samples (a) Nb-ion implaned, (b) Nb- and N-ion implanted one.
Fig. 2. RBS spectra of ion implanted samples (a) Nb-ion implaned, (b) Nb- and N-ion implanted one.
implantation, nitrogen ions were supplied using Kafumann type ion source. Isothermal oxidation experiments of CoNiCrAlY bond coat with and without ion implantation were carried out at 1150 °C for 50 and 100 h in air. The surface morphologies, TGO thickness, chemical composition and phase of oxide of as-sprayed and ion implanted specimens were analyzed using a SEM, an AES, a RBS and a XRD, respectively.
3. Result and discussion
E. Byon et al. / Surface & Coatings Technology 205 (2010) S435–S438
Table 1 T relative volume fraction of α-alumina and spinel oxide in as-sprayed, Nb-ion implanted, and Nb-/N-ion implanted samples after isothermal oxidation at 1150 °C for 50 and 100 h.
γ+ β Intensity, counts
C
γ+β
γ+ β
B
Oxidation time
Coating
α%
S%
50 h
As-sprayed Nb+ implanted Nb+/N+ implanted As-sprayed Nb+ implanted Nb+/N+ implanted
54.6 51.8 46.7 58.1 52.2 47.7
45.4 48.2 53.3 41.9 47.8 52.3
100 h
A
30
40
50
60
70
80
2 Theta, degree Fig. 3. XRD-patterns of the CoNiCrAlY bond coating with and without ion implantation, (A) as-sprayed, (B) Nb-ion implanted and (C) Nb/N-ions implanted bond coat.
oxidation time to 100 h, it shows a similar tendency except increased intensity. For quantitative analysis, relative volume fraction of all αalumina and spinel oxide are counted and summarized in Table 1. The relative volume fraction of α-alumina decreases with Nb and Nb/N-ion implantation. For 50 h oxidation, the fraction of α-alumina is 54.6%
(a) Intensity, counts
50 hrs
a: Al 2O 3 b: (Ni,Co)(Cr,Al) 2O 4 γ+ β
C
γ+ β
b
γ+ β
B A a
30
40
50
a
60
S437
a 70
without ion implantation. However, the fraction is reduced to 51.8% and 46.7% by Nb and Nb/N-ion implantation. In case of 100 h oxidation, 58.1% of α-alumina fraction is reduced to 52.2% and 47.7% by Nb and Nb/N-ion implantation. Fig. 5 shows TGO thickness variation of CoNiCrAlY bond-coats after isothermal oxidation at 1150 °C for 50 h and 100 h. It shows 30% and 50% retardation of TGO growth by N and Nb/N-ion implantation, respectively. Therefore, it is obvious that Nb and N-ion implantations have a promising way to improve the TBC service life by retardation of the growth of TGO in the MCrAlY bond coat. It is reported that Nbion implantation enhances the formation of a more stable Al2O3-rich layer during initial stage of oxidation [7]. From the current results, in contrast, it might be induced by compounds of Nb, nitrogen and oxygen. The implanted ions forms a non-stoichiometric NbO and NbNO compounds in the bond coat as shown In Fig. 2. These compounds seem to hinder to diffuse-out of Al from bond coat and diffuse-in oxygen from the environment. Since the diffusion is essential to form the oxide at the metal gas interface, the layer formed by the non-stoichiometric NbO and NbNO compounds act as an oxidation barrier resulting to the suppression of TGO growth. Furthermore, the NbNO compound is preferred to retard TGO growth compared to the NbO compound layer. Refractory- and reactivemetal nitrides generally possess high melting points and a low dissociation partial pressure. These properties indicate that the refractory-and reactive-metal nitrides are highly stable compounds and can be used in layer forms to provide barriers against diffusion and high-temperature environmental degradation [8]. The effect of ion species on the formation of TGO and its mechanism will be continued.
80
2 Theta, degree 10
(b) C
a: Al 2O 3 b: (Ni,Co)(Cr,Al) 2O 4
γ+ β
γ+ β
b
8
γ+ β
b
B
A a aa
As-sprayed Nb-ion implanted Nb/N-ion implanted
9
TGO thickness (μm)
Intensity, counts
100 hrs
a a
7 6 5 4 3 2 1
30
40
50
60
70
80
2 Theta, degree
0
50
100
Oxidation time (hrs) Fig. 4. XRD-patterns of the CoNiCrAlY bond coating with and without ion implantation after isothermal oxidation for (a) 50 h and (b) 100 h, (A) as-sprayed, (B) Nb-ion implanted and (C) Nb/N-ions implanted bond coat.
Fig. 5. TGO thickness of CoNiCrAlY bond-coats after isothermal oxidation for 50 h and 100 h at 1150 °C.
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4. Conclusion Oxidation behavior of CoNiCrAlY bond-coats with Nb and N-ion implantation at 1150 °C in air for 50 h and 100 h was investigated. From the XRD analysis, the XRD peaks of CoNiCrAlY with ion implantation (Nb, N) were broadened. After oxidation tests, relative volume fraction of α-Al2O3 decreases with Nb and N-ion implantation. The TGO thickness formed on CoNiCrAlY coating with Nb/N-ion implantation after isothermal oxidation for 50 and 100 h at 1150 °C reduces dramatically. It is concluded that Nb and N-ion implantations can slower the growth of the TGO, which indicates the effective improvement of the oxidation resistance of CoNiCrAlY bond-coats.
References [1] [2] [3] [4] [5]
A. Sambasiva Rao Gurrappa, Surf. Coat. Technol. 201 (2006) 3016. Z.L. Dong, K.A. Khor, Y.W. Gu, Surf. Coat. Technol. 114 (1999) 181. V.K. Tolpygo, D.R. Clarke, K.S. Murphy, Surf. Coat. Technol. 188–189 (2004) 62. Jiing-Herng Lee, Pi-Chuen Tsai, Jyh-Wei Lee, Thin Solid Films 517 (2009) 5253. A. Anders, S. Anders, I.G. Brown, M.Y. Kim, Nuclear Inst. and Methods in Physics Research B 102 1-4 (1995) 132. [6] I.G. Brown, M.R. Dickinson, J.E. Galvin, X. Godechot, R.A. MacGill, J. Mater. Eng. 13 (1991) 217. [7] Y.C. Zhu, Y. Zhang, X.Y. Li, K. Fujita, N. Iwamoto, Oxid. Met. 55 (½) (2001) 119. [8] H.L. Du, P.K. Datta, D. Griffin, A. Aljarany, J.S. Burnell-Gray, Oxid. Met. 60 (½) (2003) 29.
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
Effect of ion implantation on growth of thermally grown oxide in MCrAlY coating for TBC Eungsun Byon ⁎, Shihong Zhang 1, Sung-Hun Lee, Goo-Hyun Lee, Sik-Chol Kwon Material Processing Research Department, Korea Institute of Materials Science (KIMS), 66 Sangnam-dong, Changwon, Kyungnam, 641-010, Republic of Korea
a r t i c l e
i n f o
Available online 26 September 2010 Keywords: Plasma source ion implantation Thermally grown oxide Thermal barrier coating Oxidation
a b s t r a c t Thermal barrier coatings (TBCs) have been widely used in various gas turbines for aircraft propulsion and power generation. TBCs consist of a metal bond coat and a ceramic top coat of YSZ. It is generally known that the TBC′ life strongly depends on the thermally grown oxide (TGO) because failure of TBCs occurs when the TGO reached a critical thickness. In this study, ion implantation of novel elements has been made on the bond coat which acts as an oxidation barrier for suppressing the TGO growth. The effects of type of ion implanted elements on the TGO formation were investigated. The oxidized specimens at 1150 °C were characterized by SEM, XRD, RBS and AES. From the results, CoNiCrAlY bond coat with an oxidation barrier was found to be effective in suppressing growth of the TGO. © 2010 Elsevier B.V. All rights reserved.
1. Introduction The demand for improved performance in high-temperature mechanical systems has led to increasingly harsh operating environments, particularly for the components in advanced gas-turbine engines. Future improvements in gas-turbine performance will require even higher operating efficiencies, longer operating lifetimes, and reduced emissions. Achieving these requirements will necessitate still further increases in the gas inlet temperatures [1]. Thermal barrier coatings (TBCs) have been widely used in various gas turbines for aircraft propulsion and power generation. TBCs consist of a MCrAlY bond coat and a ceramic top coat of YSZ. Using this approach, temperature drop of up to 170 °C at the metal surface has been estimated, enabling the operation of gas-turbine engines at higher gas inlet temperatures [2]. It is generally known that the TBC′ life strongly depends on the thermally grown oxide (TGO) formed between bond coat and YSZ coating during service of high-temperature because spallation and/or cracking of the thickening TGO scale is the ultimate failure mechanism of commercial TBCs. [3] With increasing TGO thickness, cracks propagate by interface separation, buckling and kinking. Once the TGO spalls, it will spall together with the TBC, leaving the system with no temperature barrier protection. Many attempts have been made to suppress the TGO growth in the bond coat by third element addition such as Pt, Pd, Rh, Ir and Ru etc., preoxidation at a low pressure of oxygen environment [4]. Third element ⁎ Corresponding author. E-mail address: [email protected] (E. Byon). 1 Current address: School of Materials Science and Engineering, Anhui University of Technology, Maanshan, Anhui province 243002, China. 0257-8972/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2010.08.134
addition tends to reduce mechanical properties at a high-temperature, and it is the non-cost-effective process. Depletions of Al in the bond coat during the pre-oxidation may result in growing of spinel type oxide, which are believed to prompt the spalling of TBCs. The diffusion barrier is one of the promising technologies to retard TGO growth by isolation bond coat from oxygen from hot gas. Oxygen is essential to form the oxide of metal elements. Moreever, the coating has interfaces between bond coat and YSZ top coat. Therefore, interface failure will be another issue. In this study, ion implantation of novel elements has been made on the bond coat which acts as an oxidation barrier for suppressing the TGO growth. 2. Experimental Disc type of dimensions 25 mm × 5 mm was prepared as a substrate. The CoNiCrAlY bond coat was produced by the vacuum plasma spray (VPS) on a Ni-base alloy substrate (IN718). Prior to deposit, the substrate surface was blasted with Al2O3 grits and cleaned by transferred arc. After evacuation, the VPS spray chamber is filled with N2 gas and maintained at 60 mbar of low pressure during spraying to allow coatings of reactive metals to be produced without oxidation. Plasma spraying of bond coat was conducted on the substrate by a GTV F6 vacuum plasma spray system. Two types of ion species, Nb and N, were implanted on CoNiCrAlY bond coat using plasma source ion implantation (PSII) equipped with filtered vacuum arc source. Details of the processing can be found elsewhere [5,6]. Highly ionized Mg plasmas were generated from the filtered vacuum arc source. Then the Nb-ions were accelerated within the electric field between a sheath and substrates. The electric energy of the implantation field was 27.5 keV. For the nitrogen-ion
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E. Byon et al. / Surface & Coatings Technology 205 (2010) S435–S438
AES and RBS analysis were conducted to determine elements depth profile and doses in the nitrogen and Nb-ion implanted layer. AES depth profiles of the Nb- and Nb/N-ion implanted specimens are shown in Fig. 1. From the figure, an elemental trace for Nb and N varies gradually from the surface to the bulk without forming a distinct interface. This is one of the advantages of PSII as compared to coating process. A maximum implantation depth of Nb-ions is formed after 7 and 4 min of sputtering as shown in Fig. 1(a) and (b), respectively, indicating that Nb has been successfully implanted into the bond coat. However the amount of implanted ions of Nb in Fig. 1(a) is much larger than in Fig. 1(b). It may be caused by enhanced plasma density vicinity of the samples by additional nitrogen plasma.
RBS spectra and calculated data of the same sample as Fig. 1 are shown in Fig. 2. The Nb-ion dose is 6.28 × 1016 ions/cm2 in the sample (a). In the case of Nb and N implantation, there are pronounced Nb and N implantation. The retained ion doses of Nb and N are 5.22 × 1016 ions/cm2 and 1.69 × 1016 ions/cm2, respectively. From the RBS simulation, implanted ions seem to form compounds like nonstoichiometric NbO and NbNO for Nb-ion implanted sample and Nb and N-ions implanted one, respectively. The XRD-patterns of the as-sprayed coating with and without ion implantation are shown in Fig. 3. The XRD peaks of bond coat without implantation shows signals of the γ + β phase mainly. The Nb and Nb/ N-ion implanted coatings have similar phase compositions like in the as-sprayed one. Comparing to as-sprayed one, however, the peaks of ion implanted ones were broadened, which indicates less crystalline nature are involved. Fig. 4 shows XRD-patterns of the CoNiCrAlY bond coating with and without ion implantation after isothermal oxidation for (a) 50 h and (b) 100 h. Exposing as-sprayed and Nb, Nb/N-ion implanted specimens at 1150 °C in the air for 50 h, and 100 h, lead to significant differences in the oxidized components and thickness. After 50h oxidation, XRD-patterns of as-sprayed coating shows signal of αalumina and spinel oxide. By Nb and N-ion implantation, amounts of α-alumina and spinel oxide are reduced significantly. With increasing
Fig. 1. AES depth profiles of ion implanted samples (a) Nb-ion implaned, (b) Nb- and N-ion implanted one.
Fig. 2. RBS spectra of ion implanted samples (a) Nb-ion implaned, (b) Nb- and N-ion implanted one.
implantation, nitrogen ions were supplied using Kafumann type ion source. Isothermal oxidation experiments of CoNiCrAlY bond coat with and without ion implantation were carried out at 1150 °C for 50 and 100 h in air. The surface morphologies, TGO thickness, chemical composition and phase of oxide of as-sprayed and ion implanted specimens were analyzed using a SEM, an AES, a RBS and a XRD, respectively.
3. Result and discussion
E. Byon et al. / Surface & Coatings Technology 205 (2010) S435–S438
Table 1 T relative volume fraction of α-alumina and spinel oxide in as-sprayed, Nb-ion implanted, and Nb-/N-ion implanted samples after isothermal oxidation at 1150 °C for 50 and 100 h.
γ+ β Intensity, counts
C
γ+β
γ+ β
B
Oxidation time
Coating
α%
S%
50 h
As-sprayed Nb+ implanted Nb+/N+ implanted As-sprayed Nb+ implanted Nb+/N+ implanted
54.6 51.8 46.7 58.1 52.2 47.7
45.4 48.2 53.3 41.9 47.8 52.3
100 h
A
30
40
50
60
70
80
2 Theta, degree Fig. 3. XRD-patterns of the CoNiCrAlY bond coating with and without ion implantation, (A) as-sprayed, (B) Nb-ion implanted and (C) Nb/N-ions implanted bond coat.
oxidation time to 100 h, it shows a similar tendency except increased intensity. For quantitative analysis, relative volume fraction of all αalumina and spinel oxide are counted and summarized in Table 1. The relative volume fraction of α-alumina decreases with Nb and Nb/N-ion implantation. For 50 h oxidation, the fraction of α-alumina is 54.6%
(a) Intensity, counts
50 hrs
a: Al 2O 3 b: (Ni,Co)(Cr,Al) 2O 4 γ+ β
C
γ+ β
b
γ+ β
B A a
30
40
50
a
60
S437
a 70
without ion implantation. However, the fraction is reduced to 51.8% and 46.7% by Nb and Nb/N-ion implantation. In case of 100 h oxidation, 58.1% of α-alumina fraction is reduced to 52.2% and 47.7% by Nb and Nb/N-ion implantation. Fig. 5 shows TGO thickness variation of CoNiCrAlY bond-coats after isothermal oxidation at 1150 °C for 50 h and 100 h. It shows 30% and 50% retardation of TGO growth by N and Nb/N-ion implantation, respectively. Therefore, it is obvious that Nb and N-ion implantations have a promising way to improve the TBC service life by retardation of the growth of TGO in the MCrAlY bond coat. It is reported that Nbion implantation enhances the formation of a more stable Al2O3-rich layer during initial stage of oxidation [7]. From the current results, in contrast, it might be induced by compounds of Nb, nitrogen and oxygen. The implanted ions forms a non-stoichiometric NbO and NbNO compounds in the bond coat as shown In Fig. 2. These compounds seem to hinder to diffuse-out of Al from bond coat and diffuse-in oxygen from the environment. Since the diffusion is essential to form the oxide at the metal gas interface, the layer formed by the non-stoichiometric NbO and NbNO compounds act as an oxidation barrier resulting to the suppression of TGO growth. Furthermore, the NbNO compound is preferred to retard TGO growth compared to the NbO compound layer. Refractory- and reactivemetal nitrides generally possess high melting points and a low dissociation partial pressure. These properties indicate that the refractory-and reactive-metal nitrides are highly stable compounds and can be used in layer forms to provide barriers against diffusion and high-temperature environmental degradation [8]. The effect of ion species on the formation of TGO and its mechanism will be continued.
80
2 Theta, degree 10
(b) C
a: Al 2O 3 b: (Ni,Co)(Cr,Al) 2O 4
γ+ β
γ+ β
b
8
γ+ β
b
B
A a aa
As-sprayed Nb-ion implanted Nb/N-ion implanted
9
TGO thickness (μm)
Intensity, counts
100 hrs
a a
7 6 5 4 3 2 1
30
40
50
60
70
80
2 Theta, degree
0
50
100
Oxidation time (hrs) Fig. 4. XRD-patterns of the CoNiCrAlY bond coating with and without ion implantation after isothermal oxidation for (a) 50 h and (b) 100 h, (A) as-sprayed, (B) Nb-ion implanted and (C) Nb/N-ions implanted bond coat.
Fig. 5. TGO thickness of CoNiCrAlY bond-coats after isothermal oxidation for 50 h and 100 h at 1150 °C.
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E. Byon et al. / Surface & Coatings Technology 205 (2010) S435–S438
4. Conclusion Oxidation behavior of CoNiCrAlY bond-coats with Nb and N-ion implantation at 1150 °C in air for 50 h and 100 h was investigated. From the XRD analysis, the XRD peaks of CoNiCrAlY with ion implantation (Nb, N) were broadened. After oxidation tests, relative volume fraction of α-Al2O3 decreases with Nb and N-ion implantation. The TGO thickness formed on CoNiCrAlY coating with Nb/N-ion implantation after isothermal oxidation for 50 and 100 h at 1150 °C reduces dramatically. It is concluded that Nb and N-ion implantations can slower the growth of the TGO, which indicates the effective improvement of the oxidation resistance of CoNiCrAlY bond-coats.
References [1] [2] [3] [4] [5]
A. Sambasiva Rao Gurrappa, Surf. Coat. Technol. 201 (2006) 3016. Z.L. Dong, K.A. Khor, Y.W. Gu, Surf. Coat. Technol. 114 (1999) 181. V.K. Tolpygo, D.R. Clarke, K.S. Murphy, Surf. Coat. Technol. 188–189 (2004) 62. Jiing-Herng Lee, Pi-Chuen Tsai, Jyh-Wei Lee, Thin Solid Films 517 (2009) 5253. A. Anders, S. Anders, I.G. Brown, M.Y. Kim, Nuclear Inst. and Methods in Physics Research B 102 1-4 (1995) 132. [6] I.G. Brown, M.R. Dickinson, J.E. Galvin, X. Godechot, R.A. MacGill, J. Mater. Eng. 13 (1991) 217. [7] Y.C. Zhu, Y. Zhang, X.Y. Li, K. Fujita, N. Iwamoto, Oxid. Met. 55 (½) (2001) 119. [8] H.L. Du, P.K. Datta, D. Griffin, A. Aljarany, J.S. Burnell-Gray, Oxid. Met. 60 (½) (2003) 29.