Corrosion and nanomechanical behaviors of plasma electrolytic oxidation coated AA7020-T6 aluminum alloy

Venugopal, A.; Srinath, J.; Krishna, L. Rama; Narayanan, P. Ramesh; Sharma, S.C.; Venkitakrishnan, P. V.

doi:10.1016/j.msea.2016.02.045

Cited by 50 publications

(16 citation statements)

References 22 publications

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“…Those values show that the oxide protective coating on Ti alloy is almost 20 times higher than the untreated one. Our results, together with those of additional previous works [ 31 , 32 ], lead to the conclusion that MAO treatment can be applied to improve the corrosion resistance of metals.…”

Section: Resultssupporting

confidence: 79%

Coating Formation on Ti-6Al-4V Alloy by Micro Arc Oxidation in Molten Salt

et al. 2018

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Micro Arc Oxidation (MAO) is an electrochemical surface treatment process to produce oxide protective coatings on some metals. MAO is usually conducted in an aqueous electrolyte, which requires an intensive bath cooling and leads to the formation of a coating containing impurities that originate in the electrolyte. In the current work, we applied an alternative ceramic coating to the Ti-6Al-4V alloy using the MAO process in molten nitrate salt at a temperature of 280 °C. The obtained coating morphology, chemical and phase composition, and corrosion resistance were investigated and described. The obtained results showed that a coating of 2.5 µm was formed after 10 min of treatment, containing titanium oxide and titanium‒aluminum intermetallic phases. Morphological examination indicated that the coating is free of cracks and contains round, homogeneously distributed pores. Corrosion resistance testing indicated that the protective oxide coating on Ti alloy is 20 times more resistive than the untreated alloy.

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Section: Resultssupporting

confidence: 79%

Coating Formation on Ti-6Al-4V Alloy by Micro Arc Oxidation in Molten Salt

et al. 2018

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“…In Figure 4, the diffraction peaks of Al substrate are also found due to the strong penetration power of X-rays. A similar result was also reported in the GAXRD analysis of PEO coating on AA7020-T6 aluminum alloys [46]. There is no presence of Si3N4 peaks in the GAXRD pattern because of its broad peak nature of nano size particles in XRD.…”

Section: Voltage-time Response Of Peo Coatingssupporting

confidence: 86%

Effects of Processing Parameters on the Corrosion Performance of Plasma Electrolytic Oxidation Grown Oxide on Commercially Pure Aluminum

Mengesha

Chu

Lou

et al. 2020

Metals

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The plasma electrolyte oxidation (PEO) process has been considered an environmentally friendly surface engineering method for improving the corrosion resistance of light weight metals. In this work, the corrosion resistance of commercially pure Al and PEO treated Al substrates were studied. The PEO layers were grown on commercially pure aluminum substrates using two different alkaline electrolytes with different addition concentrations of Si 3 N 4 nanoparticles (0, 0.5 and 1.5 gL −1 ) and different duty cycles (25%, 50%, and 80%) at a fixed frequency. The corrosion properties of PEO coatings were investigated by the potentiodynamic polarization and electrochemical impedance spectroscopy test in 3.5 wt.% NaCl solutions. It showed that the weight gains, layer thickness and surface roughness of the PEO grown oxide layer increased with increasing concentrations of Si 3 N 4 nanoparticles. The layer thickness, surface roughness, pore size, and porosity of the PEO oxide layer decreased with decreasing duty cycle. The layer thickness and weight gain of PEO coating followed a linear relationship. The PEO layer grown using the Na 2 B 4 O 7 ·10H 2 O contained electrolyte showed an excellent corrosion resistance and low surface roughness than other PEO coatings with Si 3 N 4 nanoparticle additives. It is noticed that the corrosion performance of PEO coatings were not improved by the addition of Si 3 N 4 nanoparticle in the electrolytic solutions, possibly due to its detrimental effect to the formation of a dense microstructure.Metals 2020, 10, 394 2 of 21 hardness restrict their wider application in crucial environments [1,2]. One of the efficient approaches to improve these disadvantages of aluminum is by surface modification for enhancing its anticorrosion performance, such as plasma electrolytic oxidation (PEO), ion implantation, laser surfacing, diffusion treatment, thermal spraying, physical vapor deposition (PVD), chemical vapor deposition (CVD) and conversion coatings such as anodizing, etc. Among several kinds of surface modification techniques, PEO is one of the most promising surface treatment methods [3], because it is an environmentally friendly and cost-effective technique for surface engineering and a suitable method for producing thick, hard and dense ceramic coatings on light metals.PEO, also known as micro-arc oxidation (MAO) [4], is an electrochemical induced plasma surface treatment process for creating oxide ceramic coatings on light metals [5,6]. PEO is a relatively new surface modification technique which can significantly improve the hardness, corrosion and wear resistance, adhesion strength, thermal and other desirable properties of Al alloys by efficiently growing thick alumina rich ceramic coatings [7][8][9][10]. During this process, plasma discharge can cause the formation of a highly adhesive and dense oxide layer on the substrate [11,12]. PEO is also considered an environmentally friendly and cost-effective coating process with real industrial applications [3,[13][14][15][16][17][18]. Several par...

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“…[35][36][37] Such a phase gradient composite coating, even with occluded porosity in the bulk of the coating (shown in Figure 5) as created by the microscopic short-lived volcanic discharge events (shown in Figure 4), exhibits hardness in the range of 13 to 18 GPa together with extremely superior wear and corrosion resistance than the traditional HA coatings as reported earlier, which is understandable. 31,[38][39][40] Despite the presence of an interesting phase composition leading to enhanced wear and corrosion protection of Al alloys, it is noteworthy that the fatigue performance of MAO coatings is still significantly poorer than the corresponding Al alloy as discussed in detail in the following section.…”

Section: Phase Constituentsmentioning

confidence: 99%

Enhancing the high cycle fatigue life of high strength aluminum alloys for aerospace applications

Krishna

Madhavi

Sahithi

et al. 2018

Fatigue Fract Eng Mat Struct

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Hard anodized (HA) and micro arc oxidation (MAO) coatings of identical thickness were deposited on two different high strength aluminum (Al) alloys namely, 2024‐T3 and 7075‐T6. Further, as received Al alloys were also subjected to shot peening (SP) to induce subsurface compressive residual stresses followed by the MAO coating deposition (SP + MAO). The average velocity of particle‐in‐flight during the SP process was measured and utilized to calculate the kinetic energy of the peening particles. The bare and coated alloys were subjected to completely reversed stress (R = −1) rotating beam high cycle fatigue tests at five different stress levels. In addition, the bare and coated alloys were also evaluated for their tensile properties, elemental composition, phase constituents, surface, and cross‐sectional morphologies including the surface roughness (Ra, Rz) and correlated the same with the corresponding fatigue behavior. Irrespective of substrate alloy composition and stress levels investigated, the duplex SP + MAO treatment resulted in significant fatigue life enhancement over and above the fatigue life of corresponding bare (not shot peened) Al alloy, while the hard anodized and plain MAO (both without prior shot peening) continue to exhibit significant fatigue debit. Driven by the compressive residual stresses present beneath the subsurface region of SP + MAO coating interface, fractured surface examination of SP + MAO coatings clearly highlights the crack‐branching associated multiple crack deflection as the predominant operative mechanism responsible for diminishing the crack growth rate and therefore enhance the fatigue life as compared with the near linear crack extension without significant deflections leading to relative premature failure of plain MAO coated alloys.

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Corrosion and nanomechanical behaviors of plasma electrolytic oxidation coated AA7020-T6 aluminum alloy

Cited by 50 publications

References 22 publications

Coating Formation on Ti-6Al-4V Alloy by Micro Arc Oxidation in Molten Salt

Coating Formation on Ti-6Al-4V Alloy by Micro Arc Oxidation in Molten Salt

Effects of Processing Parameters on the Corrosion Performance of Plasma Electrolytic Oxidation Grown Oxide on Commercially Pure Aluminum

Enhancing the high cycle fatigue life of high strength aluminum alloys for aerospace applications

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