Structure and Property of Micro-arc Oxidation Coating Modified by Laser Melting and Solidifying on Aluminum Alloy

doi:10.3724/SP.J.1077.2013.12598

Abstract

Abstract: In order to improve performance and microstructure of micro-arc oxidation (MAO) coating, especially loose and porous characteristic, a laser melting and solidifying process (LSM) was introduced. Two kinds of samples were prepared: (1) MAO coatings, 18 μm average thickness, were produced on 6082 aluminum alloy by bipolar current pulse in Na2SiO3-KOH solution. (2) a melting process using a Nd:YAG laser was employed to modify above-mentioned MAO coatings to obtain MAO+LSM coating. Microstructure of two kinds of coatings (MAO coating and MAO+LSM coating) were examined by scanning electron microscopy. X-ray diffraction was used to determine the phase composition of the coatings. Coating hardness was tested by ultra-micro hardness tester, and corrosion performance was investigated by polarization test instrument. The results show that the MAO+LSM coating is composed of dense layer, intermediate layer and melting layer from inside to surface. The loose layer of MAO film is replaced by a dense and low porosity melting layer after LSM treatment. The occupancy of α-Al2O3 phase in MAO+LSM is improved compared with MAO coating. Hardness and anticorrosion performance of MAO+LSM coating are also further strengthened while the remelted coating keeps the same binding manner as MAO coating.

Key words: 6082 aluminum alloy, micro-arc oxidation, laser melting and solidifying, anticorrosion behavior

CLC Number:

TG174

YU Jie, WEI Dong-Bo, WANG Yan, Lü Peng-Xiang, DI Shi-Chun. Structure and Property of Micro-arc Oxidation Coating Modified by Laser Melting and Solidifying on Aluminum Alloy[J]. Journal of Inorganic Materials, 2013, 28(8): 859-863.

References

[1] Zuo Y, Zhao P H, Zhao J M. The influences of sealing methods on corrosion behavior of anodized aluminum alloys in NaCl solutions. Surface and Coatings Technology, 2003, 166(2/3): 237–242.

[2] Hu J M, Liu L, Zhang J Q, et al. Electrodeposition of silane films on aluminum alloys for corrosion protection. Progress in Organic Coatings, 2007, 58(4): 265–271.

[3] Ogurtsov N A, Puda A A, Kamarchik P, et al. Corrosion inhibition of aluminum alloy in chloride mediums by undoped and doped forms of polyaniline. Synthetic Metals, 2004, 143(1): 43.

[4] Nie X, Leyland A, Song H W, et al. Thickness effects on the mechanical properties of micro-arc discharge oxide coatings on aluminium alloys. Surface and Coatings Technology, 1999, 116: 1055–1060.

[5] Wu H H, Wang J B, Long B Y, et al. Ultra-hard ceramic coatings fabricated through microarc oxidation on aluminium alloy. Applied Surface Science, 2005, 252(5): 1545–1552.

[6] Yerokhin A L, Nie X, Leyland A, et al. Plasma electrolysis for surface engineering. Surface and Coatings Technology, 1999, 122(2/3): 73–93.

[7] Ko Y G., Lee K M, Shin K R, et al. Electrochemical corrosion properties of AZ91 Mg alloy via plasma electrolytic oxidation and subsequent annealing. Korean Journal of Metals and Materials, 2010, 48(8): 724–729.

[8] Luo H H, Cai Q Z, Wei B K. Study on the microstructure and corrosion resistance of ZrO2-containing ceramic coatings formed on magnesium alloy by plasma electrolytic oxidation. Journal of Alloys and Compounds, 2009, 474(1/2): 551–556.

[9] Guan Yong Jun, Xia Yuan, Li Guang. Growth mechanism and corrosion behavior of ceramic coatings on aluminum produced by auto control AC pulse PEO. Surface and Coatings Technology, 2008, 202(19): 4602–4612.

[10] Chang S Y, Lee D H, Kim B S, et al. Characteristics of plasma electrolytic oxide coatings on Mg-Al-Zn alloy prepared by powder metallurgy. Metals and Materials International, 2009, 15(5): 759–764.

[11] Ko Y G., Lee K M, Lee B U, et al. An electrochemical analysis of AZ91 Mg alloy processed by plasma electrolytic oxidation followed by static annealing. Journal of Alloys and Compounds, 2011, 509(S1): S468–S472.

[12] Sah Santosh Prasad, Tsuji Etsushi, Aoki Yoshitaka, et al. Cathodic pulse breakdown of anodic films on aluminium in alkaline silicate electrolyte- Understanding the role of cathodic half-cycle in AC plasma electrolytic oxidation. Corrosion Science, 2012, 55: 90–96.

[13] Lee Kang Min, Ko Young Gun, Shin Dong Hyuk. Incorporation of carbon nanotubes into micro-coatings film formed on aluminum alloy via plasma electrolytic oxidation. Materials Letters, 2011, 65(14): 2269–2273.

[14] Asquith D T, Yerokhin A L, Yates J R, et al. Effect of combined shot-peening and PEO treatment on fatigue life of 2024 Al alloy. Thin Solid Films, 2006, 515(3): 1187–1191.

[15] Khorasanian M, Dehghan A, Shariat M H, et al. Microstructure and wear resistance of oxide coatings on Ti-6Al-4V produced by plasma electrolytic oxidation in an inexpensive electrolyte. Surface and coatings Technology, 2011, 206(6): 1495–1502.

[16] Dutta-Majumdar J, Manna I. Laser surface alloying of copper with chromium II. Improvement in mechanical properties. Materials Science and Engineering: A, 1999, 268(1/2): 227–235.

[17] Amanat N, Chaminade C, Grace J. Transmission laser welding of amorphous and semi-crystalline poly-ether-ether-ketone for applications in the medical device industry. Material & Design, 2010, 31(10): 4823–4830.

[18] Espa?a Félix A, Ball Vamsi Krishna, Bandyopadhyay Amit. Laser surface modification of AISI 410 stainless steel with brass for enhanced thermal properties. Surface and Coatings Technology., 2010, 204(15): 2510–2517.

[19] Wang A H, Wang W Y, Xie C S, et al. CO2 laser-induced structure changes on a zircon refractory. Applied Surface Science, 2004, 227(1-4): 104–113.

[20] Harimkar Sandip P, Dahotre Narendra B. Microindentation fracture behavior of laser surface modified alumina ceramic. Scripta Materialia, 2008, 58(7): 545–548.

[21] Harimkar S, Dahotre N B. Laser assisted densification of surface porosity in structural alumina ceramic. Physica Status Solidi (a), 2007, 204(4): 1105–1113.

[22] Harimkara Sandip P, Dahotre Narendra B. Characterization of microstructure in laser surface modified alumina ceramic. Materials Characterization, 2008, 59(6): 700–707.

[23] Mateos J, Cuetos J M, Fernandez E, et al. Tribological properties of plasma sprayed and laser remelted 75/25 Cr3C2/NiCr coatings. Tribology International, 2001, 34(5): 345–351.

[24] Yerokhin A L, Snizhko L O, Gurevina N L, et al. Spatial characteristics of discharge phenomena in plasma electrolytic oxidation of aluminium alloy. Surface and Coatings Technology, 2004, 177-178: 779–783.