scholarly journals Incorporation mechanism of colloidal TiO2 nanoparticles and their effect on properties of coatings grown on 7075 Al alloy from silicate-based solution using plasma electrolytic oxidation

2021 ◽  
Vol 31 (12) ◽  
pp. 3659-3676
Author(s):  
Mehri HASHEMZADEH ◽  
Keyvan RAEISSI ◽  
Fakhreddin ASHRAFIZADEH ◽  
Amin HAKIMIZAD ◽  
Monica SANTAMARIA
2020 ◽  
Vol 58 (6) ◽  
pp. 699
Author(s):  
Quang-Phu Tran ◽  
Van-Da Dao ◽  
Van-Hoi Pham

Plasma electrolytic oxidation (PEO) has earned much attention due to its powerful and easy formation of hard and corrosion-resistant oxide layers on valve metals, such as Al alloys. Here we report the effects of current density (CD) on microstructure and properties of coatings on 6061 Al alloy by PEO using direct current mode. The electrolyte contains the chemicals of Na2SiO3, Na2WO4´2H2O, and NaH2PO2´H2O. The CDs adopted 5.0, 7.5, 10.0, and 12.5 A/dm2, respectively, for a fixed PEO time of 30 min. The thickness, surface morphology, phase composition, hardness, and corrosion resistance of PEO coatings as the function of the applied CD have been studied and discussed. Studied results show the coating thickness is proportional to the applied CD. When the applied CD increases 2.5 times from 5.0 to 12.5 A/dm2, the growth rate of oxide layers increased by more than 3.5 times, from 0.423 to 1.493 μm/min, respectively. SEM images are characterized by a reduction in the ratio of agglomerate-bumps-region/flatten-region as applied CD increases. However, cracks and larger pores appear when the applied CD is higher than 10.0 A/dm2. X-ray diffraction pattern shows that the main phases of Al, g-Al2O3, α-Al2O3, and W are contained in all coatings. PEO coated sample has the highest hardness of 1290 HV and highest polarization resistance of 8.80 ´ 106 Wcm2 obtained at applied CD 10 A/dm2 which shows the best performance of the coating. The variation in coating performance is explained by microstructure details, specifically phases, compositions of oxide-layers, and micro-pores and cracks.


2015 ◽  
Vol 269 ◽  
pp. 114-118 ◽  
Author(s):  
Yeon Sung Kim ◽  
Hae Woong Yang ◽  
Ki Ryong Shin ◽  
Young Gun Ko ◽  
Dong Hyuk Shin

2011 ◽  
Vol 158 (10) ◽  
pp. C325 ◽  
Author(s):  
Kang Min Lee ◽  
Jong Oh Jo ◽  
Eung Seok Lee ◽  
Bongyoung Yoo ◽  
Dong Hyuk Shin

2015 ◽  
Vol 53 (8) ◽  
pp. 535-540 ◽  
Author(s):  
Young Gun Ko ◽  
Dong Hyuk Shin ◽  
Hae Woong Yang ◽  
Yeon Sung Kim ◽  
Joo Hyun Park ◽  
...  

2019 ◽  
Vol 1328 ◽  
pp. 012099
Author(s):  
A V Kolomeichenko ◽  
S N Sharifullin ◽  
V N Logachev ◽  
Yu A Kuznetsov ◽  
I N Kravchenko ◽  
...  

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