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45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding”
Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding” Shuxin Niu a, Shu Cai a,n, Tielong Liu b,nn, Huan Zhao a, Xuexin Wang a, Mengguo Ren a, Kai Huang a, Xiaodong Wu b a b
Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072, People's Republic of China Shanghai Changzheng Hospital, Shanghai 200003, People's Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 18 June 2014 Accepted 15 November 2014
A strong interfacial bonded 45S5 glass-ceramic coating was fabricated on AZ31B magnesium alloy using a sol gel dip-coating technique followed by thermal treatment at temperature of 480 1C and different Ar pressures. When the pressure was 0.6 MPa and held for 90 min, the bonding strength reached 26.8 MPa, much higher than that of samples thermally treated at the same temperature without any pressure. The strong interfacial bonding strength is mainly attributed to the solid solution reaction accelerated by the atomic diffusion due to the pressure. & 2014 Published by Elsevier B.V.
Keywords: Adhesion Magnesium alloy Ceramics Superplasticity Diffusion bonding
1. Introduction Magnesium alloys have been regarded as the potential biodegradable implant materials due to their desirable mechanical properties, biocompatibilities and biodegradabilities. However, the high reactivity in chloride solutions (including the human body fluid or blood plasma) leads to the fast loss of mechanical integrity and the release of hydrogen, which limited their extensive biomedical applications [1,2]. Surface modifications, especially, protective surface coatings, are often applied to improve the corrosion resistance of magnesium alloys. Among the bioactive coating materials, bioglasss 45S5, as a commercially available inorganic material, possesses excellent bioactivity, favorable biocompatibility and controllable biodegradability [3]. Moreover, the sol gel derived 45S5 glass possesses comparatively low synthesizing temperature and glass transition temperature, making it more suitable to be used as protective coatings on magnesium alloys with low melting points. Nevertheless, some researchers reported that during immersion in SBF, peeling off and cracking of coatings led to failure in protecting the magnesium alloy substrates for a long time, which were caused by low adhesion strength of coatings and substrate [4,5]. Superplasticity diffusion bonding is a process for making a monolithic joint through the formation of bonds at atomic level, as
n
Corresponding author. Tel.: þ 86 22 27425069. Corresponding author. Tel.: þ 86 21 63610109. E-mail addresses: [email protected] (S. Cai), [email protected] (T. Liu).
nn
a result of closure of the mating surfaces due to the local plastic deformation (at elevated temperature and using pressure) which aids interdiffusion of elements across the joint interface [6]. In this study, 45S5 glass-ceramic coatings were prepared on magnesium alloy substrate with a combination of sol gel and dip-coating methods. To obtain high bonding strength, the coated samples were thermally treated under different pressures. The effect of pressure on the bonding strength was investigated.
2. Experimental procedure The substrate material was AZ31B magnesium alloy (12 mm 12 mm 2 mm). All sample surfaces were ground with 2000 grit SiC paper to ensure the same surface roughness. The 45S5 glass sol was synthesized by tetraethyl orthosilicate (TEOS), triethyl phosphate (TEP), NaNO3 and Ca(NO3)2 4H2O. The ratios of TEOS, TEP, NaNO3 and Ca(NO3)2 4H2O were designed in reference to the nominal composition [7] of 45.0% SiO2 24.5% CaO 24.5% Na2O 6.0% P2O5 (all in wt%). All of the chemicals were consecutively added to 0.1 M of HNO3 aqueous solution and the solution was stirred for 3 h at room temperature. Thereafter, the substrates were dipped into the sols for designated time, aged at room temperature for 24 h and then dried at 60 1C for 1 h. Subsequently, all the samples were thermally treated under Ar pressure of 0.3 MPa, 0.6 MPa or 0.9 MPa at temperature of 480 1C for 90 min (denoted as 0.3P-45S5, 0.6P-45S5 and 0.9P-45S5 respectively), using a Pressure Sintering Furnace (PVSGgr20/20, Japan).
http://dx.doi.org/10.1016/j.matlet.2014.11.057 0167-577X/& 2014 Published by Elsevier B.V.
Please cite this article as: Niu S, et al. 45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding”. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.11.057i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
S. Niu et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Fig. 1. Surface and cross-sectional micrographs of sample N-45S5 (a) and sample 0.6P-45S5 (b).
The preparation of 45S5 coatings without any pressure (denoted as N-45S5) was also performed as the above process. The surface and cross-section morphologies were observed by a field-emission scanning electron microscope (FE-SEM, JOEL6700F, Japan), and elemental analysis was characterized by a energy dispersive spectrometer (EDS). X-ray diffraction (XRD, Rigaku, Japan) was used to determine the phase composition of the coatings. Bonding strengths of the coatings to the substrates were measured using a universal tensile testing machine (AGS-H, Shimadzu, Japan). The test samples were prepared by bonding the coated sample to two Al alloy supports using a jig and a tensile rate of 0.5 mm/min was employed. Five bonding strength tests were performed for each sample.
3. Results and discussion Fig. 1a and b shows the surface morphologies and the crosssectional micrograph of the coated magnesium alloys under or without pressure, respectively. A crack-free, smooth and homogeneous coating was obtained on the sample N-45S5 (Fig. 1a), while all samples prepared under different pressures exhibited crack-free, uneven surfaces. The image of sample 0.6P-45S5 was presented as a representative (Fig. 1b) due to the similarity of all P-45S5 samples. Crosssection of sample N-45S5 and 0.6P-45S5 (insets of Fig. 1a and b) showed homogeneous and well adhered coatings on magnesium alloy. However, the boundary line between the compact coating and substrate of sample 0.6P-45S5 (Fig. 1b) was more obscure than that of sample N-45S5 (Fig. 1a). During the metallographic preparation by polishing the cross-sections, a few detached cracks of sample N-45S5 tended to be generated, suggesting that they had relatively low adherence to the substrate. The adhesion strength between coatings and substrates plays a significant role in the long-term stability of implants coated with bioactive coatings [5]. The influence of pressure on the bonding strength of coatings to substrate is shown in Fig. 2a. The bonding strength of samples thermally treated at 480 1C for 90 min without any pressure was (14.272.0) MPa. While the bonding strength increased with the increase of Ar pressure for the same heat treatment temperature and holding time. When the pressure was 0.3 MPa, the bonding strength was (17.571.9) MPa. Further increasing the pressure, the bonding strength reached the maximum value of (26.872.7) MPa at a pressure of 0.6 MPa, and then decreased to (22.772.2) MPa when the pressure was up to 0.9 MPa. The XRD patterns of the naked AZ31B alloy and samples thermally treated under or without pressure have been given in Fig. 2b. For the coated sample N-45S5, large quantity of amorphous phase characterized by the background levels was detected, and crystalline phase Na2Ca2Si3O9 (JCPDS no. 22-1455) was also observed in agreement with
previous report by Cacciotti et al. [8]. As the pressure increased to 0.3 MPa, minor crystalline Na2Ca4Mg2Si4O15 (JCPDS no. 42-1484) phases appeared and the peaks of Na2Ca2Si3O9 became sharper while the background decreased, demonstrating the increasing amount of crystallization. Further increasing the pressure to 0.6 MPa, a new crystalline Na2Mg2Si2O7 (JCPDS no. 53-0626) phase was detected and the peaks of Na2Ca2Si3O9 and Na2Ca4Mg2Si4O15 became much sharper, suggesting the further crystallization. When the pressure increased to 0.9 MPa, seldom amorphous phase was left and the peaks of Na2Ca2Si3O9, Na2Ca4Mg2Si4O15 and Na2Mg2Si2O7 became the sharpest. Obviously, with the increase of thermal treatment pressure, the amount of crystallization increases. The appearance of Mg atoms in the new crystalline phase suggested that the solid solution reaction happened at the interface of coating and substrate during thermal treatment under pressure. The bonding strength of sample N-45S5 mainly came from the mechanical adhesion strength between coating and substrate [9], which was confirmed by the adhesion failure morphology and chemical composition (Fig. 3). The major failure mode of sample N-45S5 was adhesion failure that occurred between the coating and substrate and there was a minimum of cohesion failure that happened inside the coating (Fig. 3a). The EDS spectrum revealed very little Si, P, Na and Ca remaininged on the substrate surface, suggesting that almost all the coatings were peeled from the substrate during the test process (Fig. 3b). When Ar pressure was applied at the temperature of 480 1C, which is higher than both temperatures of 0.5Ts (Ts is the solidus temperature of AZ31B magnesium alloy, 325 1C) and the glass transition temperature (Tg ¼ 380 1C) of 45S5 [3,6], the interface bonding between the coating and substrate will carry on by interdiffusion. It means the contact area between the two surfaces expanded due to the superplasticity of the magnesium alloy and the flowability of the glass matrix in the process of pressure at high temperature. Subsequently, the boundary line formed at the original interface gradually disappeared as the contact area expanded with the pressurizing time extension (inset of Fig. 1b). As a result of interdiffusion across the interface, the formation of a complex solid solution is produced (Fig. 2b), which made the bonding strength increase with the pressure increasing. When the pressure was 0.6 MPa, the samples had the highest bonding strength (Fig. 2). The adhesion failure topography of sample 0.6P-45S5 showed that the area fraction of cohesion failure drastically increased from around 3 8% (Fig. 3a) to around 80–90% (Fig. 3c), which contributed to the highest bonding strength. In the EDS spectrum (Fig. 3d), the existence of Si, P, Na and Ca on the surface confirmed that parts of coatings still adhered firmly on the substrate. Hence, the actual bonding strength should be much higher than 26.8 MPa for sample 0.6P-45S5. However, when the pressure reached 0.9 MPa, the adhesion strength decreased to 22.7 MPa. The reduction of the strength might be associated with
Please cite this article as: Niu S, et al. 45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding”. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.11.057i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
S. Niu et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Fig. 2. The bonding strength of the coatings to substrates (a) and the XRD patterns of the coated sample thermally treated at 480 1C and different pressures (b).
Fig. 3. Typical adhesion failure of the coatings: (a) sample N-45S5, (b) EDS analysis of Part A, (c) sample 0.6P-45S5, and (d) EDS analysis of Part B.
the large crystallization of sample 0.9P-45S5. The large crystallization from glass matrix during the process of thermal treatment under Ar pressure of 0.9 MPa would lead to high internal stresses within the coatings due to the different thermal expansion coefficients between glass matrix and crystallized phases [10,11], and reduced structural relaxation [12]. Finally the high internal stresses as dominant effect led to a decrease of bonding strength compared with sample 0.6P-45S5.
90 min. With the increase of the pressure, the bonding strength increased. The coated samples thermally treated under pressure of 0.6 MPa had the highest bonding strength (26.8 MPa), which was as much as 88.7% higher than that of thermal treated samples without any pressure (14.2 MPa). The strong interfacial bonded 45S5 glassceramic coatings could be a potential material for development of corrosion resistance and bioactivity of magnesium alloys.
4. Conclusions
Acknowledgments
In this study, strong interfacial bonded 45S5 glass-ceramic coatings were synthesized by thermal treatment at 480 1C and Ar pressure for
The authors are grateful to National Natural Science Foundation of China for financial support (Grant nos. 51372166, 81271954) and
Please cite this article as: Niu S, et al. 45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding”. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.11.057i
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S. Niu et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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acknowledge Mr. Qing Huang (Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences) for their help in the experimental work. References [1] Kannan MB, Raman RKS. Biomaterials 2008;29:2306–14. [2] Ren L, Lin X, Tan LL, Yang K. Mater Lett 2011;65:3509–11. [3] Huang K, Cai S, Xu GH, Ye XY, Dou Y, Ren MG, et al. J Alloys Compd 2013;580:290–7. [4] López AJ, Otero E, Rams. J Surf Coat Technol 2010;205:2375–85.
[5] Dou Y, Cai S, Ye XY, Xu GH, Huang K, Wang XX, et al. Surf Coat Technol 2013;228:154–61. [6] Somekawa H, Watanabe H, Mukai T, Higashi K. Scr Mater 2003;48:1249–54. [7] Chen QZ, Thompson ID, Boccaccini AR. Biomaterials 2006;27:2414–25. [8] Cacciotti I, Lombardi M, Bianco A, Ravaglioli A, Montanaro L. J Mater Sci: Mater Med 2012;23:1849–66. [9] Cai S, Dou Y, Huang K, Zhang RY, Xu GH, Ye XJ. Sci Adv Mater 2013;5:1–9. [10] Malekmohammadi F, Rouhaghdam SA, Shahrabi TJ. Non-Cryst Solids 2011;357:1141–6. [11] Wang XX, Cai S, Xu GH, Ye XY, Ren MG, Huang K. J Sol–Gel Sci Technol 2013;67:629–38. [12] Ohno K, Uchiyama H, Kozuka H. J Appl Phys 2012;111(1 9):014901.
Please cite this article as: Niu S, et al. 45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding”. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.11.057i
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Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding” Shuxin Niu a, Shu Cai a,n, Tielong Liu b,nn, Huan Zhao a, Xuexin Wang a, Mengguo Ren a, Kai Huang a, Xiaodong Wu b a b
Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072, People's Republic of China Shanghai Changzheng Hospital, Shanghai 200003, People's Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 18 June 2014 Accepted 15 November 2014
A strong interfacial bonded 45S5 glass-ceramic coating was fabricated on AZ31B magnesium alloy using a sol gel dip-coating technique followed by thermal treatment at temperature of 480 1C and different Ar pressures. When the pressure was 0.6 MPa and held for 90 min, the bonding strength reached 26.8 MPa, much higher than that of samples thermally treated at the same temperature without any pressure. The strong interfacial bonding strength is mainly attributed to the solid solution reaction accelerated by the atomic diffusion due to the pressure. & 2014 Published by Elsevier B.V.
Keywords: Adhesion Magnesium alloy Ceramics Superplasticity Diffusion bonding
1. Introduction Magnesium alloys have been regarded as the potential biodegradable implant materials due to their desirable mechanical properties, biocompatibilities and biodegradabilities. However, the high reactivity in chloride solutions (including the human body fluid or blood plasma) leads to the fast loss of mechanical integrity and the release of hydrogen, which limited their extensive biomedical applications [1,2]. Surface modifications, especially, protective surface coatings, are often applied to improve the corrosion resistance of magnesium alloys. Among the bioactive coating materials, bioglasss 45S5, as a commercially available inorganic material, possesses excellent bioactivity, favorable biocompatibility and controllable biodegradability [3]. Moreover, the sol gel derived 45S5 glass possesses comparatively low synthesizing temperature and glass transition temperature, making it more suitable to be used as protective coatings on magnesium alloys with low melting points. Nevertheless, some researchers reported that during immersion in SBF, peeling off and cracking of coatings led to failure in protecting the magnesium alloy substrates for a long time, which were caused by low adhesion strength of coatings and substrate [4,5]. Superplasticity diffusion bonding is a process for making a monolithic joint through the formation of bonds at atomic level, as
n
Corresponding author. Tel.: þ 86 22 27425069. Corresponding author. Tel.: þ 86 21 63610109. E-mail addresses: [email protected] (S. Cai), [email protected] (T. Liu).
nn
a result of closure of the mating surfaces due to the local plastic deformation (at elevated temperature and using pressure) which aids interdiffusion of elements across the joint interface [6]. In this study, 45S5 glass-ceramic coatings were prepared on magnesium alloy substrate with a combination of sol gel and dip-coating methods. To obtain high bonding strength, the coated samples were thermally treated under different pressures. The effect of pressure on the bonding strength was investigated.
2. Experimental procedure The substrate material was AZ31B magnesium alloy (12 mm 12 mm 2 mm). All sample surfaces were ground with 2000 grit SiC paper to ensure the same surface roughness. The 45S5 glass sol was synthesized by tetraethyl orthosilicate (TEOS), triethyl phosphate (TEP), NaNO3 and Ca(NO3)2 4H2O. The ratios of TEOS, TEP, NaNO3 and Ca(NO3)2 4H2O were designed in reference to the nominal composition [7] of 45.0% SiO2 24.5% CaO 24.5% Na2O 6.0% P2O5 (all in wt%). All of the chemicals were consecutively added to 0.1 M of HNO3 aqueous solution and the solution was stirred for 3 h at room temperature. Thereafter, the substrates were dipped into the sols for designated time, aged at room temperature for 24 h and then dried at 60 1C for 1 h. Subsequently, all the samples were thermally treated under Ar pressure of 0.3 MPa, 0.6 MPa or 0.9 MPa at temperature of 480 1C for 90 min (denoted as 0.3P-45S5, 0.6P-45S5 and 0.9P-45S5 respectively), using a Pressure Sintering Furnace (PVSGgr20/20, Japan).
http://dx.doi.org/10.1016/j.matlet.2014.11.057 0167-577X/& 2014 Published by Elsevier B.V.
Please cite this article as: Niu S, et al. 45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding”. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.11.057i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
S. Niu et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
Fig. 1. Surface and cross-sectional micrographs of sample N-45S5 (a) and sample 0.6P-45S5 (b).
The preparation of 45S5 coatings without any pressure (denoted as N-45S5) was also performed as the above process. The surface and cross-section morphologies were observed by a field-emission scanning electron microscope (FE-SEM, JOEL6700F, Japan), and elemental analysis was characterized by a energy dispersive spectrometer (EDS). X-ray diffraction (XRD, Rigaku, Japan) was used to determine the phase composition of the coatings. Bonding strengths of the coatings to the substrates were measured using a universal tensile testing machine (AGS-H, Shimadzu, Japan). The test samples were prepared by bonding the coated sample to two Al alloy supports using a jig and a tensile rate of 0.5 mm/min was employed. Five bonding strength tests were performed for each sample.
3. Results and discussion Fig. 1a and b shows the surface morphologies and the crosssectional micrograph of the coated magnesium alloys under or without pressure, respectively. A crack-free, smooth and homogeneous coating was obtained on the sample N-45S5 (Fig. 1a), while all samples prepared under different pressures exhibited crack-free, uneven surfaces. The image of sample 0.6P-45S5 was presented as a representative (Fig. 1b) due to the similarity of all P-45S5 samples. Crosssection of sample N-45S5 and 0.6P-45S5 (insets of Fig. 1a and b) showed homogeneous and well adhered coatings on magnesium alloy. However, the boundary line between the compact coating and substrate of sample 0.6P-45S5 (Fig. 1b) was more obscure than that of sample N-45S5 (Fig. 1a). During the metallographic preparation by polishing the cross-sections, a few detached cracks of sample N-45S5 tended to be generated, suggesting that they had relatively low adherence to the substrate. The adhesion strength between coatings and substrates plays a significant role in the long-term stability of implants coated with bioactive coatings [5]. The influence of pressure on the bonding strength of coatings to substrate is shown in Fig. 2a. The bonding strength of samples thermally treated at 480 1C for 90 min without any pressure was (14.272.0) MPa. While the bonding strength increased with the increase of Ar pressure for the same heat treatment temperature and holding time. When the pressure was 0.3 MPa, the bonding strength was (17.571.9) MPa. Further increasing the pressure, the bonding strength reached the maximum value of (26.872.7) MPa at a pressure of 0.6 MPa, and then decreased to (22.772.2) MPa when the pressure was up to 0.9 MPa. The XRD patterns of the naked AZ31B alloy and samples thermally treated under or without pressure have been given in Fig. 2b. For the coated sample N-45S5, large quantity of amorphous phase characterized by the background levels was detected, and crystalline phase Na2Ca2Si3O9 (JCPDS no. 22-1455) was also observed in agreement with
previous report by Cacciotti et al. [8]. As the pressure increased to 0.3 MPa, minor crystalline Na2Ca4Mg2Si4O15 (JCPDS no. 42-1484) phases appeared and the peaks of Na2Ca2Si3O9 became sharper while the background decreased, demonstrating the increasing amount of crystallization. Further increasing the pressure to 0.6 MPa, a new crystalline Na2Mg2Si2O7 (JCPDS no. 53-0626) phase was detected and the peaks of Na2Ca2Si3O9 and Na2Ca4Mg2Si4O15 became much sharper, suggesting the further crystallization. When the pressure increased to 0.9 MPa, seldom amorphous phase was left and the peaks of Na2Ca2Si3O9, Na2Ca4Mg2Si4O15 and Na2Mg2Si2O7 became the sharpest. Obviously, with the increase of thermal treatment pressure, the amount of crystallization increases. The appearance of Mg atoms in the new crystalline phase suggested that the solid solution reaction happened at the interface of coating and substrate during thermal treatment under pressure. The bonding strength of sample N-45S5 mainly came from the mechanical adhesion strength between coating and substrate [9], which was confirmed by the adhesion failure morphology and chemical composition (Fig. 3). The major failure mode of sample N-45S5 was adhesion failure that occurred between the coating and substrate and there was a minimum of cohesion failure that happened inside the coating (Fig. 3a). The EDS spectrum revealed very little Si, P, Na and Ca remaininged on the substrate surface, suggesting that almost all the coatings were peeled from the substrate during the test process (Fig. 3b). When Ar pressure was applied at the temperature of 480 1C, which is higher than both temperatures of 0.5Ts (Ts is the solidus temperature of AZ31B magnesium alloy, 325 1C) and the glass transition temperature (Tg ¼ 380 1C) of 45S5 [3,6], the interface bonding between the coating and substrate will carry on by interdiffusion. It means the contact area between the two surfaces expanded due to the superplasticity of the magnesium alloy and the flowability of the glass matrix in the process of pressure at high temperature. Subsequently, the boundary line formed at the original interface gradually disappeared as the contact area expanded with the pressurizing time extension (inset of Fig. 1b). As a result of interdiffusion across the interface, the formation of a complex solid solution is produced (Fig. 2b), which made the bonding strength increase with the pressure increasing. When the pressure was 0.6 MPa, the samples had the highest bonding strength (Fig. 2). The adhesion failure topography of sample 0.6P-45S5 showed that the area fraction of cohesion failure drastically increased from around 3 8% (Fig. 3a) to around 80–90% (Fig. 3c), which contributed to the highest bonding strength. In the EDS spectrum (Fig. 3d), the existence of Si, P, Na and Ca on the surface confirmed that parts of coatings still adhered firmly on the substrate. Hence, the actual bonding strength should be much higher than 26.8 MPa for sample 0.6P-45S5. However, when the pressure reached 0.9 MPa, the adhesion strength decreased to 22.7 MPa. The reduction of the strength might be associated with
Please cite this article as: Niu S, et al. 45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding”. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.11.057i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
S. Niu et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
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Fig. 2. The bonding strength of the coatings to substrates (a) and the XRD patterns of the coated sample thermally treated at 480 1C and different pressures (b).
Fig. 3. Typical adhesion failure of the coatings: (a) sample N-45S5, (b) EDS analysis of Part A, (c) sample 0.6P-45S5, and (d) EDS analysis of Part B.
the large crystallization of sample 0.9P-45S5. The large crystallization from glass matrix during the process of thermal treatment under Ar pressure of 0.9 MPa would lead to high internal stresses within the coatings due to the different thermal expansion coefficients between glass matrix and crystallized phases [10,11], and reduced structural relaxation [12]. Finally the high internal stresses as dominant effect led to a decrease of bonding strength compared with sample 0.6P-45S5.
90 min. With the increase of the pressure, the bonding strength increased. The coated samples thermally treated under pressure of 0.6 MPa had the highest bonding strength (26.8 MPa), which was as much as 88.7% higher than that of thermal treated samples without any pressure (14.2 MPa). The strong interfacial bonded 45S5 glassceramic coatings could be a potential material for development of corrosion resistance and bioactivity of magnesium alloys.
4. Conclusions
Acknowledgments
In this study, strong interfacial bonded 45S5 glass-ceramic coatings were synthesized by thermal treatment at 480 1C and Ar pressure for
The authors are grateful to National Natural Science Foundation of China for financial support (Grant nos. 51372166, 81271954) and
Please cite this article as: Niu S, et al. 45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding”. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.11.057i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 Q2131 132
S. Niu et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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1 2 3 4 5 6 7 8 9 10 11 12
acknowledge Mr. Qing Huang (Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences) for their help in the experimental work. References [1] Kannan MB, Raman RKS. Biomaterials 2008;29:2306–14. [2] Ren L, Lin X, Tan LL, Yang K. Mater Lett 2011;65:3509–11. [3] Huang K, Cai S, Xu GH, Ye XY, Dou Y, Ren MG, et al. J Alloys Compd 2013;580:290–7. [4] López AJ, Otero E, Rams. J Surf Coat Technol 2010;205:2375–85.
[5] Dou Y, Cai S, Ye XY, Xu GH, Huang K, Wang XX, et al. Surf Coat Technol 2013;228:154–61. [6] Somekawa H, Watanabe H, Mukai T, Higashi K. Scr Mater 2003;48:1249–54. [7] Chen QZ, Thompson ID, Boccaccini AR. Biomaterials 2006;27:2414–25. [8] Cacciotti I, Lombardi M, Bianco A, Ravaglioli A, Montanaro L. J Mater Sci: Mater Med 2012;23:1849–66. [9] Cai S, Dou Y, Huang K, Zhang RY, Xu GH, Ye XJ. Sci Adv Mater 2013;5:1–9. [10] Malekmohammadi F, Rouhaghdam SA, Shahrabi TJ. Non-Cryst Solids 2011;357:1141–6. [11] Wang XX, Cai S, Xu GH, Ye XY, Ren MG, Huang K. J Sol–Gel Sci Technol 2013;67:629–38. [12] Ohno K, Uchiyama H, Kozuka H. J Appl Phys 2012;111(1 9):014901.
Please cite this article as: Niu S, et al. 45S5 bioactive glass-ceramic coated magnesium alloy with strong interfacial bonding strength by “superplasticity diffusion bonding”. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.11.057i
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