- Email: [email protected]
Research on Micro-arc Oxidation Coatings with Thermal Control on Magnesium Alloy
Available online at www.sciencedirect.com
ScienceDirect Physics Procedia 50 (2013) 185 – 190
International Federation for Heat Treatment and Surface Engineering 20th Congress Beijing, China, 23-25 October 2012
Research on micro-arc oxidation coatings with thermal control on magnesium alloy Sizhen Li*, Jingying Bai, Li Feng, Ligong Zhang, Qingxin CuiWenwu Jiang, Guimei Zhao Beijing Spacecrafts, China Academy of Space Technology, 100190, Beijing, China
Abstract
The Micro-arc coatings with antisepsis and thermal control function was grew in situ on magnesium alloys by Micro-arc oxidation (MAO) method in order to satisfy the antisepsis and thermal control demand of magnesium alloys for spacecraft. The effect of electrolyte formulation and temperature were reviewed by orthogonal test. The appearance and bonding strength of Micro-arc coatings were checked by eyeballing and draw-testing. Hemisphere emissivity ?H was tested by using hemisphere emissivity testing apparatus. The results showed that the micro-arc coatings were homogeneous and uniform when the Electrolyte components correspond to temperature. Hemisphere emissivity ?H test result showed that [email protected] the Performance of micro-arc coatings were qualified with technology guideline. © 2013 2013 The The Authors. © Authors. Published Publishedby byElsevier ElsevierB.V. B.V. Selection and and peer-review Selection peer-review under underresponsibility responsibilityofofthe theChinese ChineseHeat HeatTreatment TreatmentSociety. Society Keywords: Magnesium alloys; Micro-arc coatings; Antisepsis; Thermal control;
* Corresponding author. Tel.: +86-010-68378594. E-mail address:[email protected]
1875-3892 © 2013 The Authors. Published by Elsevier B.V. Selection and peer-review under responsibility of the Chinese Heat Treatment Society doi:10.1016/j.phpro.2013.11.030
186
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190
1. Introduction Magnesium and its alloys are very attractive materials, because of their advantages, such as light weight, high strength-to-weight ratio, low elastic modulus and good electromagnetic shielding characteristics(Cole G S and Sherman A M,1995),( Mordike B L and Ebert T,2001). The density of magnesium is only 2/3 that of aluminum and 1/4 that of iron, therefore, magnesium alloys are expected the ideal materials as structural materials in the aerospace fields(Zhong H et al.,2002),( Li F M et al.,1998). Micro-arc oxidation (MAO) is a new surface treatment method used to form a thick oxide coatings on magnesium substrate by plasma discharge in aqueous solution on substrate surface under high voltage(Gray J E and Luan B,2002),( Yerokhin A L et al.,1999). Dielectric oxide passive film forms on the metal substrate/electrolyte interface when the sample is applied considerably to a low anodic potential in the electrolyte. The Micro-arc coatings with antisepsis and thermal control functional was grew in situ on magnesium alloys by Micro-arc oxidation method in order to satisfy the antisepsis and thermal control demand of magnesium alloys for spacecraft. The Micro-arc coatings with antisepsis on Magnesium alloys were extensively researched, but the Micro-arc coatings with antisepsis and thermal control function was not reported in publication. In the present work,, the effects of the technical parameters such as the prescription of electrolyte solutions and the temperature on the performance of the Micro-arc coatings were researched by orthogonal test method, the performance of the Micro-arc coatings such as the equality, the binding energy and the stability of the thermal control functional were obviously enhanced, the performance of the Micro-arc coatings can meet with the requirement of the Magnesium alloys thermal control configuration product in aerospace industry fields.
2. Experimental 2.1. Material AZ40M magnesium alloy specimens were used as substrates,its chemic compose was described in table 1. Table 1. Chemical compositions of AZ40M magnesium alloys (mass fraction, %) Al
Zn
Mn
Si
Fe
Cu
Be
trace element
Mg
3.0~4.0
0.20~0.80
0.15~0.50
M0.10
M0.10
M0.05
M0.01
M0.30
remains
2.2. Preparation of coatings Fig. 1 shows the schematic diagram of experimental setup for MAO. The Micro-arc oxidation power supply was bidirectional impulse electrical source, stainless steel Storage as the cathode, magnesium alloy workpiece anode. The preparation of the Micro-arc coatings with antisepsis and thermal control function on magnesium alloys was as follow: the preparation before oxidation Ndegrease by organic compoundN wash Ndegrease by chemic reagent N washN MAON washN drying.
187
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190
Fig. 1. Schematic diagram of experimental setup for MAO 1-cooling equipment2-circle waterbath3-Storage of MAO (stainless steel cathode)4- temperature sensor; 5- magnesium alloy workpiece (anode);6- impeller;7- electrolyte;8- Micro-arc oxidation power supply
2.3. Performance testing The appearance was checked-up by eyeballing method, the binding energy of the Micro-arc coatings was tested by drawstring with a certain extent glutinosity adhesive tape, the surface and cross-section morphologies were token by scanning electron microscopy(SEM), and the hemisphere emissivity H was measured by AE radiometer. 3. Results and discussion Table 2 shows that the most important factors and their levels, such as the main composition concentration, the content of additive A, the content of additive B and the temperature. Table 2. Factors and levels graph factor
the main composition concentration/g·L-1
the content of additive A/g·L-1
the content of additive B/g·L-1
temperature/ C
1
40
0.5
2.5
510
2
60
1
5
1520
3
80
2
10
2530
As shown in Table 3, the performance of Micro-arc coatings was evident influenced by the factors and their levels showed in Table 2. The appearance and the binding energy of the Micro-arc coatings was rest with the cooperation of the four factors. The appearance and the binding energy of the Micro-arc coatings are eligible when the four factors and their levels well suited each other. The appearance and the binding energy of the Micro-arc coatings is disqualified which desquamate from the Magnesium alloys substrate when the factors and their levels illfitting suited each other. The hemisphere emissivity ?H of Micro-arc coatings was obviously influenced by the matching extent between the content of additive A and additive B. The [email protected] when the content of additive A and additive B well suited each other. The colour and lustre of the Micro-arc coatings is grey and the ?H <0.85 when the content of additive A and additive B ill-fitting suited. As shown in Table 3, the techniques parameter of the 2# and the 5# are well suited each other, the appearance, the binding energy and the ?H all satisfy with the technical indexes.
188
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190 Table 3. Experimental result statistic charts graph
the appearance
the binding energy
the hemisphere emissivity ?H
accord with the guideline
510
ecumenical
disqualification
0.83
N
5
510
excellent
eligible
0.86
Y
2
10
2530
deformed
disqualification
/
N
0.5
5
2530
ecumenical
disqualification
0.83
N
1
10
510
excellent
eligible
0.85
Y
2
2.5
1520
disfigurement
disqualification
0.83
N
0.5
10
1520
disfigurement
disqualification
0.82
N
80
1
2.5
2530
deformed
disqualification
/
N
80
2
5
510
disfigurement
disqualification
0.83
N
sequence number
the main composition concentration/g·L-1
the content of additive A/g·L-1
the content of additive B/g·L-1
temperature/
1#
40
0.5
2.5
2#
40
1
3#
40
4#
60
5#
60
6#
60
7#
80
8# 9#
C
Fig.2 and Fig.3 show the surface morphology of the MAO coatings. As shown in Fig. 2, the micro-arc oxidation coatings of the 2# sample is favorable, and the binding energy is excellent, and the micro-arc oxidation coatings of the 7# sample is coarse and sloopy, the binding energy is incompetent, the coatings will be fall off form the magnesium alloys substrates when tested by drawstring with a certain extent glutinosity adhesive tape. As shown in Fig. 3, the surface morphology of the 2# sample is poriferous, meshed and well-proportioned, the surface morphology of the 7# sample is aggregate by floccule and asymmetrical.
(a)
(b) Fig. 2. Morphology of micro-arc oxidation coatings with thermal control: (a) 2#, (b) 7#
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190
(a)
(b) Fig. 3. Surface morphology of the MAO coatings: (a) 2#, (b) 7#
Fig. 4 shows that the cross-section morphology of micro-arc oxidation coatings, the binding energy of microarc oxidation coatings of the 2# sample is remarkable, there is no crackle between the coatings and the magnesium alloys substrate, the binding energy of micro-arc oxidation coatings of the 7# sample is substandard, there is prominent crackle between the coatings and the magnesium alloys substrate which is coincident with the Fig 2.
(b)
(a)
Fig. 4.The cross-section morphology of micro-arc oxidation coatings with thermal control: (a) 2#, (b) 7#
4. Conclusions (1) The Micro-arc coatings with antisepsis and thermal control functional on magnesium alloys can be prepared by Micro-arc oxidation (MAO) method. (2) The performance of Micro-arc coatings were significantly influenced by the matching of factors which including the main composition concentration, the content of additive A, the content of additive B and the temperature. (3) The performance of Micro-arc coatings of the 2# and the 7# sample are excellent and eligible, indicated that the parameter of the 2# and the 7# are true of requirement. References Cole G S,Sherman A M. Light weight materials for automotive applications. Journal of Materials Characterization, 1995, 35:3-9.
189
190
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190
Mordike B L, Ebert T. Magnesium properties applications-potential. Journal of Materials Science and Engineering A, 2001,302:37-45. Zhong H, Liu P Y, Zhou TT. Applications and prosperis of magnesium and its alloys in airspace. Journal of Aviation engineeringMaintenance, 2002(4):41-42. Li F M, Qian X Y, Li J G. Application and development trend of rate each in aviation industry.Journal of Materials Engineering 1998(6):11-13. Gray J E, Luan B.Protective coatings on magnesium and its alloys-A critical review.Journal of Alloys and Compounds,2002,336(12):88-113. Yerokhin A L, Nie X, Leyland A, Matthews A, Doqey S J.Plasma electrolysis for surface engineering.Surf Coat Tech,1999,122(2):73-93.
ScienceDirect Physics Procedia 50 (2013) 185 – 190
International Federation for Heat Treatment and Surface Engineering 20th Congress Beijing, China, 23-25 October 2012
Research on micro-arc oxidation coatings with thermal control on magnesium alloy Sizhen Li*, Jingying Bai, Li Feng, Ligong Zhang, Qingxin CuiWenwu Jiang, Guimei Zhao Beijing Spacecrafts, China Academy of Space Technology, 100190, Beijing, China
Abstract
The Micro-arc coatings with antisepsis and thermal control function was grew in situ on magnesium alloys by Micro-arc oxidation (MAO) method in order to satisfy the antisepsis and thermal control demand of magnesium alloys for spacecraft. The effect of electrolyte formulation and temperature were reviewed by orthogonal test. The appearance and bonding strength of Micro-arc coatings were checked by eyeballing and draw-testing. Hemisphere emissivity ?H was tested by using hemisphere emissivity testing apparatus. The results showed that the micro-arc coatings were homogeneous and uniform when the Electrolyte components correspond to temperature. Hemisphere emissivity ?H test result showed that [email protected] the Performance of micro-arc coatings were qualified with technology guideline. © 2013 2013 The The Authors. © Authors. Published Publishedby byElsevier ElsevierB.V. B.V. Selection and and peer-review Selection peer-review under underresponsibility responsibilityofofthe theChinese ChineseHeat HeatTreatment TreatmentSociety. Society Keywords: Magnesium alloys; Micro-arc coatings; Antisepsis; Thermal control;
* Corresponding author. Tel.: +86-010-68378594. E-mail address:[email protected]
1875-3892 © 2013 The Authors. Published by Elsevier B.V. Selection and peer-review under responsibility of the Chinese Heat Treatment Society doi:10.1016/j.phpro.2013.11.030
186
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190
1. Introduction Magnesium and its alloys are very attractive materials, because of their advantages, such as light weight, high strength-to-weight ratio, low elastic modulus and good electromagnetic shielding characteristics(Cole G S and Sherman A M,1995),( Mordike B L and Ebert T,2001). The density of magnesium is only 2/3 that of aluminum and 1/4 that of iron, therefore, magnesium alloys are expected the ideal materials as structural materials in the aerospace fields(Zhong H et al.,2002),( Li F M et al.,1998). Micro-arc oxidation (MAO) is a new surface treatment method used to form a thick oxide coatings on magnesium substrate by plasma discharge in aqueous solution on substrate surface under high voltage(Gray J E and Luan B,2002),( Yerokhin A L et al.,1999). Dielectric oxide passive film forms on the metal substrate/electrolyte interface when the sample is applied considerably to a low anodic potential in the electrolyte. The Micro-arc coatings with antisepsis and thermal control functional was grew in situ on magnesium alloys by Micro-arc oxidation method in order to satisfy the antisepsis and thermal control demand of magnesium alloys for spacecraft. The Micro-arc coatings with antisepsis on Magnesium alloys were extensively researched, but the Micro-arc coatings with antisepsis and thermal control function was not reported in publication. In the present work,, the effects of the technical parameters such as the prescription of electrolyte solutions and the temperature on the performance of the Micro-arc coatings were researched by orthogonal test method, the performance of the Micro-arc coatings such as the equality, the binding energy and the stability of the thermal control functional were obviously enhanced, the performance of the Micro-arc coatings can meet with the requirement of the Magnesium alloys thermal control configuration product in aerospace industry fields.
2. Experimental 2.1. Material AZ40M magnesium alloy specimens were used as substrates,its chemic compose was described in table 1. Table 1. Chemical compositions of AZ40M magnesium alloys (mass fraction, %) Al
Zn
Mn
Si
Fe
Cu
Be
trace element
Mg
3.0~4.0
0.20~0.80
0.15~0.50
M0.10
M0.10
M0.05
M0.01
M0.30
remains
2.2. Preparation of coatings Fig. 1 shows the schematic diagram of experimental setup for MAO. The Micro-arc oxidation power supply was bidirectional impulse electrical source, stainless steel Storage as the cathode, magnesium alloy workpiece anode. The preparation of the Micro-arc coatings with antisepsis and thermal control function on magnesium alloys was as follow: the preparation before oxidation Ndegrease by organic compoundN wash Ndegrease by chemic reagent N washN MAON washN drying.
187
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190
Fig. 1. Schematic diagram of experimental setup for MAO 1-cooling equipment2-circle waterbath3-Storage of MAO (stainless steel cathode)4- temperature sensor; 5- magnesium alloy workpiece (anode);6- impeller;7- electrolyte;8- Micro-arc oxidation power supply
2.3. Performance testing The appearance was checked-up by eyeballing method, the binding energy of the Micro-arc coatings was tested by drawstring with a certain extent glutinosity adhesive tape, the surface and cross-section morphologies were token by scanning electron microscopy(SEM), and the hemisphere emissivity H was measured by AE radiometer. 3. Results and discussion Table 2 shows that the most important factors and their levels, such as the main composition concentration, the content of additive A, the content of additive B and the temperature. Table 2. Factors and levels graph factor
the main composition concentration/g·L-1
the content of additive A/g·L-1
the content of additive B/g·L-1
temperature/ C
1
40
0.5
2.5
510
2
60
1
5
1520
3
80
2
10
2530
As shown in Table 3, the performance of Micro-arc coatings was evident influenced by the factors and their levels showed in Table 2. The appearance and the binding energy of the Micro-arc coatings was rest with the cooperation of the four factors. The appearance and the binding energy of the Micro-arc coatings are eligible when the four factors and their levels well suited each other. The appearance and the binding energy of the Micro-arc coatings is disqualified which desquamate from the Magnesium alloys substrate when the factors and their levels illfitting suited each other. The hemisphere emissivity ?H of Micro-arc coatings was obviously influenced by the matching extent between the content of additive A and additive B. The [email protected] when the content of additive A and additive B well suited each other. The colour and lustre of the Micro-arc coatings is grey and the ?H <0.85 when the content of additive A and additive B ill-fitting suited. As shown in Table 3, the techniques parameter of the 2# and the 5# are well suited each other, the appearance, the binding energy and the ?H all satisfy with the technical indexes.
188
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190 Table 3. Experimental result statistic charts graph
the appearance
the binding energy
the hemisphere emissivity ?H
accord with the guideline
510
ecumenical
disqualification
0.83
N
5
510
excellent
eligible
0.86
Y
2
10
2530
deformed
disqualification
/
N
0.5
5
2530
ecumenical
disqualification
0.83
N
1
10
510
excellent
eligible
0.85
Y
2
2.5
1520
disfigurement
disqualification
0.83
N
0.5
10
1520
disfigurement
disqualification
0.82
N
80
1
2.5
2530
deformed
disqualification
/
N
80
2
5
510
disfigurement
disqualification
0.83
N
sequence number
the main composition concentration/g·L-1
the content of additive A/g·L-1
the content of additive B/g·L-1
temperature/
1#
40
0.5
2.5
2#
40
1
3#
40
4#
60
5#
60
6#
60
7#
80
8# 9#
C
Fig.2 and Fig.3 show the surface morphology of the MAO coatings. As shown in Fig. 2, the micro-arc oxidation coatings of the 2# sample is favorable, and the binding energy is excellent, and the micro-arc oxidation coatings of the 7# sample is coarse and sloopy, the binding energy is incompetent, the coatings will be fall off form the magnesium alloys substrates when tested by drawstring with a certain extent glutinosity adhesive tape. As shown in Fig. 3, the surface morphology of the 2# sample is poriferous, meshed and well-proportioned, the surface morphology of the 7# sample is aggregate by floccule and asymmetrical.
(a)
(b) Fig. 2. Morphology of micro-arc oxidation coatings with thermal control: (a) 2#, (b) 7#
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190
(a)
(b) Fig. 3. Surface morphology of the MAO coatings: (a) 2#, (b) 7#
Fig. 4 shows that the cross-section morphology of micro-arc oxidation coatings, the binding energy of microarc oxidation coatings of the 2# sample is remarkable, there is no crackle between the coatings and the magnesium alloys substrate, the binding energy of micro-arc oxidation coatings of the 7# sample is substandard, there is prominent crackle between the coatings and the magnesium alloys substrate which is coincident with the Fig 2.
(b)
(a)
Fig. 4.The cross-section morphology of micro-arc oxidation coatings with thermal control: (a) 2#, (b) 7#
4. Conclusions (1) The Micro-arc coatings with antisepsis and thermal control functional on magnesium alloys can be prepared by Micro-arc oxidation (MAO) method. (2) The performance of Micro-arc coatings were significantly influenced by the matching of factors which including the main composition concentration, the content of additive A, the content of additive B and the temperature. (3) The performance of Micro-arc coatings of the 2# and the 7# sample are excellent and eligible, indicated that the parameter of the 2# and the 7# are true of requirement. References Cole G S,Sherman A M. Light weight materials for automotive applications. Journal of Materials Characterization, 1995, 35:3-9.
189
190
Sizhen Li et al. / Physics Procedia 50 (2013) 185 – 190
Mordike B L, Ebert T. Magnesium properties applications-potential. Journal of Materials Science and Engineering A, 2001,302:37-45. Zhong H, Liu P Y, Zhou TT. Applications and prosperis of magnesium and its alloys in airspace. Journal of Aviation engineeringMaintenance, 2002(4):41-42. Li F M, Qian X Y, Li J G. Application and development trend of rate each in aviation industry.Journal of Materials Engineering 1998(6):11-13. Gray J E, Luan B.Protective coatings on magnesium and its alloys-A critical review.Journal of Alloys and Compounds,2002,336(12):88-113. Yerokhin A L, Nie X, Leyland A, Matthews A, Doqey S J.Plasma electrolysis for surface engineering.Surf Coat Tech,1999,122(2):73-93.