Properties and Structure of PEO Treated Aluminum Alloy

Abstract

Plasma electrolytic oxidation (PEO) coatings were formed on 7075 aluminum alloy in silicateborate based electrolyte with different duty cycles. The physical and chemical properties of the PEO coatings were thoroughly investigated. The wearing and corrosion properties of the coatings were evaluated by wearing experiments and potentiodynamic polarization tests, respectively. The results showed that the micro-hardness of the coatings first increased and then decreased with the increasing duty cycle. As a results, the wearing resistance of the coatings first increased and then decreased with the increasing duty cycle. Composition analysis proved that the coatings were mainly composed of α-Al₂O₃ and γ-Al₂O₃. The presence of wear scars on the worn surface morphology demonstrates that the three-body rolling was the main wear mechanism for coated specimen. The corrosion study showed that the coating formed in the mixed electrolyte with duty cycle of 80% showed the most superior corrosion resistance.

Keywords

7075 aluminum alloy / plasma electrolytic oxidation (PEO) / wearing / corrosion / friction coefficient

References

[1] Wen L, Wang Y, Zhou Y, et al. Corrosion Evaluation of Microarc Oxidation Coatings Formed on 2024 Aluminium Alloy[J]. Corros. Sci., 2010, 52(8): 2687-2696.

[2] Ding H Y, Dai Z D, Skuiry S C, et al. Corrosion Wear Behaviors of Micro-arc Oxidation Coating of Al₂O₃ on 2024Al in Different Aqueous Environments at Fretting Contact[J]. Tribol. Int., 2010, 43(5–6): 868-875.

[3] Zhang Y, Fan W, Du H Q, et al. Microstructure and Wearing Properties of PEO Coatings: Effects of and TiO₂[J]. Surf. Rev. Lett., 2018, 25(1): 1850102

[4] Jiang Y, Zhang Y, Bao Y, et al. Sliding Wear Behavior of Plasma Electrolytic Oxidation Coating on Pure Aluminium[J]. Wear, 2011, 271(9–10): 1667-1670.

[5] Wang W B, Dong P, Wang H Y, et al. Synergistic Corrosion Inhibition Effect of Molybdate and Phosphate Ions for Anodic Oxidation Film Formed on 2024 Aluminum Alloy[J]. J. Wuhan Univ. Technol., 2018, 32(7): 426-432.

[6] Sui Y W, Chen X, Wang R, et al. Wear Behavior of In-situ TiC Particles Reinforced Aluminum Matrix Composite[J]. J. Wuhan Univ. Technol., 2017, 32(7): 552-556.

[7] Xiang N, Song R G, Zhao J, et al. Microstructure and Mechanical Properties of Ceramic Coatings Formed on 6063 Aluminium Alloy by Micro-arc Oxidation[J]. Trans. Nonferrous Met. Soc. China, 2015, 25(10): 3323-3328.

[8] Lv G, Gu W, Chen H, et al. Characteristic of Ceramic Coatings on Aluminum by Plasma Electrolytic Oxidation in Silicate and Phosphate Electrolyte[J]. Appl. Surf. Sci., 2006, 253(5): 2947-2952.

[9] Lukiyanchuk I V, Rudnev V S, Kuryavyi V G, et al. Surface Morphology, Composition and Thermal Behavior of Tungsten-containing Anodic Spark Coatings on Aluminium Alloy[J]. Thin Solid Films, 2016, 446(1): 54-60.

[10] Xiang N, Song R G, Xiang B, et al. A Study on Photocatalytic Activity of Micro-arc Oxidation TiO₂ Films and Ag⁺/MAO-TiO₂ Composite Films[J]. Appl. Surf. Sci., 2015, 347(30): 454-460.

[11] Xiang N, Song R G, Li H, et al. Study on Microstructure and Electrochemical Corrosion Behavior of PEO Coatings Formed on Aluminum Alloy[J]. J. Mater. Eng. Perform., 2015, 24(12): 5022-5031.

[12] Lim TS, Ryu HS, Hong SH. Electrochemical Corrosion Properties of CeO₂-containing Coatings on AZ31 Magnesium Alloys Prepared by Plasma Electrolytic Oxidation[J]. Corr. Sci., 2012, 62(9): 104-111.

[13] Bayati M R, Golestani-Fard F, Moshfegh A Z. Visible Photodecomposition of Methylene Blue over Micro Arc Oxidized WO₃-loaded TiO₂ Nano-porous Layers[J]. Appl. Catal. A, 2010, 382(2): 322-331.

[14] Wang J H, Wang J, Lu Y, et al. Effects of Single Pulse Energy on the Properties of Ceramic Coating Prepared by Micro-arc Oxidation on Ti Alloy[J]. Appl. Surf. Sci., 2015, 324(1): 405-413.

[15] Tadića N S, Stojadinovića S, Radićb N, et al. Characterization and Photocatalytic Properties of Tungsten Doped TiO₂ Coatings on Aluminum Obtained by Plasma Electrolytic Oxidation[J]. Surf. Coat. Tech., 2016, 305(11): 192-199.

[16] Wang X, Zhu Z, Li Y, et al. Characterization of Micro-arc Oxidation Coatings on 6N01 Aluminum Alloy Under Different Electrolyte Temperature Control Modes[J]. J. Mater. Eng. Perform., 2018, 27(4): 1-8.

[17] Yu C, Cui L Y, Zhou Y F, et al. Self-degradation of Micro-arc Oxidation/Chitosan Composite Coating on Mg-4Li-1Ca Alloy[J]. Surf. Coat. Technol., 2018, 344(6): 1-11.

[18] Xiang N, Song R G, Zhuang J J, et al. Effects of Current Density on Microstructure and Properties of Plasma Electrolytic Oxidation Ceramic Coatings Formed on 6063 Aluminum Alloy[J]. Trans. Nonferrous Met. Soc. China, 2016, 26(3): 806-813.

[19] Dehnavi V, Luan B L, Shoesmith D W, et al. Effect of Duty Cycle and Applied Current Frequency on Plasma Electrolytic Oxidation (PEO) Coating Growth Behavior[J]. Surf. Coat. Technol., 2013, 226(7): 100-107.

[20] Stojadinovic S, Vasilic R, Belca I, et al. Characterization of the Plasma Electrolytic Oxidation of Aluminium in Sodium Tungstate[J]. Corros. Sci., 2010, 52(10): 3258-3265.

[21] Zhou X, Thompson G E, Skeldon P, et al. Film Formation and Detachment during Anodizing of Al-Mg Alloys[J]. Corros. Sci., 1999, 41(8): 1599-1613.

[22] Liu F, Xu J, Wang F, et al. Biomimetic Deposition of Apatite Coatings on Micro-arc Oxidation Treated Biomedical NiTi Alloy[J]. Sur. Coat. Technol., 2010, 204(20): 3294-3299.

[23] Sabatini G, Ceschini L, Martini C, et al. Improving Sliding and Abrasive Wear Behaviour of Cast A356 and Wrought AA7075 Aluminium Alloys by Plasma Electrolytic Oxidation[J]. Mater. Design, 2010, 31(2): 816-828.

[24] Srinivasan P B, Liang J, Blawert C, et al. Characterization of Calcium Containing Plasma Electrolytic Oxidation Coatings on AM50 Magnesium Alloy[J]. Appl. Surf. Sci., 2010, 256(12): 4017-4022.

[25] Liang J, Srinivasan P B, Blawert C, et al. Comparison of Electrochemical Corrosion Behaviour of MgO and ZrO₂ Coatings on AM50 Magnesium Alloy Formed by Plasma Electrolytic Oxidation[J]. Corros. Sci., 2009, 51(10): 2483-2492.

[26] Zhang R F, Zhang S F, Shen Y L, et al. Influence of Sodium Borate Concentration on Properties of Anodic Coatings Obtained by Micro Arc Oxidation on Magnesium Alloys[J]. Appl. Surf. Sci., 2012, 258(17): 6602-6610.