Effect of Power Duty Cycle on Plasma Electrolytic Oxidation of A356-Nb2O5 Metal Matrix Composites

Bahador, Reyhan; Hosseinabadi, Navid; Yaghtin, Amirhossein

doi:10.1007/s11665-021-05597-4

Cited by 10 publications

(2 citation statements)

References 51 publications

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“…Qian et al [ 4 ] found that the negative current can increase the growth rate of PEO coatings on the one hand and reduce the discrete pores inside the coatings on the other. Tsai et al [ 5 ], Melhem et al [ 6 ] and Bahador et al [ 7 ] all overcame the defects formed when the anodic charge is highger than the cathodic charge during the plasma electrolytic oxidation of aluminum alloys by increasing the cathodic charge. Interestingly, when the cathodic current is higher than the anodic current, a unique discharge phenomenon called a “soft spark” is generated during the plasma electrolytic oxidation of aluminum alloys.…”

Section: Introductionmentioning

confidence: 99%

Study of Coating Growth Direction of 6061 Aluminum Alloy in Soft Spark Discharge of Plasma Electrolytic Oxidation

Wang,

Yang,

Liu

et al. 2024

Materials

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Conventional plasma electrolytic oxidation treatments produce oxide coatings with micron-scale discharge pores, resulting in insulation and wear and corrosion resistance far below that expected of highly dense Al2O3 coatings. The introduction of cathodic polarization during the plasma electrolytic oxidation process, especially when the applied cathode-to-anode current ratio (Rpn) is greater than 1, triggers a unique plasma discharge phenomenon known as “soft sparking”. The soft spark discharge mode significantly improves the densification of the anode ceramic layer and facilitates the formation of the high-temperature α-Al2O3 phase within the coating. Although the soft spark discharge phenomenon has been known for a long time, the growth behavior of the coating under its discharge mode still needs to be studied and improved. In this paper, the growth behavior of the coating before and after soft spark discharge is investigated with the help of the micro-morphology, phase composition and element distribution of a homemade fixture. The results show that the ceramic layer grows mainly along the oxide–electrolyte direction before the soft spark discharge transformation; after the soft spark discharge, the ceramic layer grows along the oxide–substrate direction. It was also unexpectedly found that, under soft spark discharge, the silicon element only exists on the outside of the coating, which is caused by the large size and slow migration of SiO32−, which can only enter the ceramic layer and participate in the reaction through the discharge channel generated by the strong discharge. In addition, it was also found that the relative phase content of α-Al2O3 in the coating increased from 0.487 to 0.634 after 10 min of rotary spark discharge, which is an increase of 30.2% compared with that before the soft spark discharge transition. On the other hand, the relative phase content of α-Al2O3 in the coating decreased from 0.487 to 0.313 after 20 min of transfer spark discharge, which was a 55.6% decrease compared to that before the soft spark discharge transformation.

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Section: Introductionmentioning

confidence: 99%

Study of Coating Growth Direction of 6061 Aluminum Alloy in Soft Spark Discharge of Plasma Electrolytic Oxidation

Wang,

Yang,

Liu

et al. 2024

Materials

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“…Soft sparking discharge was initially observed in Al-based alloys. Tsai et al [13], Melhem et al [14], and Bahador et al [15] used the method of increasing the cathode charge to overcome the discharge channels and defects that are formed when the anode charge is greater than the cathode charge during the MAO of aluminum alloys. The results indicated that after a period of MAO processing, the anode voltage decreases and enters the stage where an extremely small spark is observed.…”

Section: Introductionmentioning

confidence: 99%

Soft Sparking Discharge Mechanism of Micro-Arc Oxidation Occurring on Titanium Alloys in Different Electrolytes

Qiu

et al. 2022

Coatings

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Soft sparking during micro-arc oxidation can form a ceramic coating with high hardness and high bond strength on titanium alloy while avoiding the continuous strong micro-arc that can damage the substrate properties and the integrity of the coating. Existing studies have reported that the soft spark discharge is significantly influenced by the electrolyte anions, and the detailed mechanism of its influence remains unclear. Therefore, we considered four monolithic electrolytes, namely Na2B4O7, NaF, Na3PO4, and Na2SiO3, for the bipolar pulsed micro-arc oxidation (MAO) treatment of the Ti6Al4V alloy to investigate the mechanism of the soft sparking discharge and the affections of different electrolytes on the soft sparking discharge. The results showed that soft spark discharges were observed in both Na2SiO3 and Na3PO4 electrolytes while not in Na2B4O7 and NaF electrolytes. We attributed this situation to the fact that the deposition of Si and P elements in the coating changed the structure and passivation ability of the coating and affected the rate of ion transport and electron tunneling in the coating, resulting in forming a thick and dense, soft spark MAO inner layer. Additionally, the soft sparking discharge facilitated particle deposition and did not destroy the structure of the initial film layer, and also had no significant effect on the corrosion resistance.

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Laser Sintered Ti-6Al-4V Alloy Coated with Plasma Electrolytic Oxidation: Influence of Duty Cycle and Frequency on Morphological, Structural, and Corrosion Properties

Premchand

Lokeshkumar

Manojkumar

et al. 2022

J. of Materi Eng and Perform

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Effect of Power Duty Cycle on Plasma Electrolytic Oxidation of A356-Nb2O5 Metal Matrix Composites

Cited by 10 publications

References 51 publications

Study of Coating Growth Direction of 6061 Aluminum Alloy in Soft Spark Discharge of Plasma Electrolytic Oxidation

Study of Coating Growth Direction of 6061 Aluminum Alloy in Soft Spark Discharge of Plasma Electrolytic Oxidation

Soft Sparking Discharge Mechanism of Micro-Arc Oxidation Occurring on Titanium Alloys in Different Electrolytes

Laser Sintered Ti-6Al-4V Alloy Coated with Plasma Electrolytic Oxidation: Influence of Duty Cycle and Frequency on Morphological, Structural, and Corrosion Properties

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