• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.29.1-29.1
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• 2018

양극산화 표면처리 방법의 일종인 플라즈마 전해산화(PEO, Plasma electrolytic oxidation)는 금속 소재에 양극 전압을 인가하여 고경도의 산화 피막을 금속 표면에 형성시키는 표면처리 기술이다. PEO 공정은 피막의 국부적 유전체 파괴에 의한 아크의 발생을 동반하며, 형성된 산화 피막이 아크 발생에 의한 높은 열에 의해 결정화 되어 일반적인 양극산화 피막보다 우수한 경도와 내마모성을 가진다. 하지만 PEO 공정은 고전압을 필요로 하여 일반적인 양극산화 처리보다 소모되는 전력량이 많으며, 아크 발생에 의해 형성된 피막의 표면 거칠기가 높기 때문에 활용 분야가 제한되거나 후속 연마 공정을 필요로 하는 단점이 존재한다. 본 연구에서는 전류 파형이 알루미늄 합금의 플라즈마 전해산화 피막의 형성 거동에 미치는 영향을 직류 및 펄스전류를 사용하여 연구하였다. NaOH 및 $Na_2SiO_3$가 혼합된 전해액에서 직류 전류 밀도, 전압, 펄스폭을 달리하여 알루미늄 합금에 전류를 인가할 때 발생되는 아크의 거동, 형성된 산화 피막의 두께, 거칠기, 경도, 표면 및 단면 구조를 비교 분석하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.133-133
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• 2012

플라즈마 전해산화(Plasma Electrolytic Oxidation;PEO) 피막은 Anodizing 피막에 비해 화학 부식성, 플라즈마 부식성 등의 특성이 뛰어나지만 표면 거칠기는 Anodizing 피막이 우수한 것으로 알려져 있다. 본 연구에서는 PEO 피막의 제작시 사용된 Power Supply의 펄스 변조(PAM, PWM 방식)을 통하여 표면 거칠기를 제어하는 방법에 대한 실험을 수행하였다. 그리고 펄스 변조 전후의 시편의 내전압과 플라즈마 부식성 등의 특성을 비교하였다. 또한 펄스 변조 전후 PEO 시편과 Anodizing 시편의 표면 거칠기, 내전압, 플라즈마 부식성 등의 특성을 비교하였다.

• Corrosion Science and Technology
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• 제9권1호
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• pp.8-11
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• 2010

During PEO (plasma-electrolytic-oxidation) treatment of titanium, the relationship between the thickness of oxide film and the measured electrical information was investigated. A simple real time monitoring method based on the electrical information being gathered during PEO treatment is proposed. The proposed method utilizes the current flowing from a high frequency voltage source to calculate the resistance of an oxide film, which is converted into the thickness of an oxide film. This monitoring method can be implemented in PEO system in which an oxide film is grown by constant or pulsed voltage/current sources.

• 한국재료학회지
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• 제27권9호
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• pp.495-500
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• 2017

Oxide layers were formed by an environmentally friendly plasma electrolytic oxidation (PEO) process on AZ91 Mg alloy. PEO treatment also resulted in strong adhesion between the oxide layer and the substrate. The influence of the KF electrolytic solution and the structure, composition, microstructure, and micro-hardness properties of the oxide layer were investigated. It was found that the addition of KF instead of KOH to the $Na_2SiO_3$ electrolytic solution increased the electrical conductivity. The oxide layers were mainly composed of MgO and $Mg_2SiO_4$ phases. The oxide layers exhibited solidification particles and pancake-shaped oxide melting. The pore size and surface roughness of the oxide layer decreased considerably with an increase in the concentration of KF, while densification of the oxide layers increased. It is shown that the addition of KF to the basis electrolyte resulted in fabricating of an oxide layer with higher surface hardness and smoother surface roughness on Mg alloys by the PEO process. The uniform thickness of the oxide layer formed on the Mg alloy substrates was largely determined by the electrolytic solution with KF, which suggests that the composition of the electrolytic solution is one of the key factors controlling the uniform thickness of the oxide layer.

• 한국표면공학회지
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• 제56권4호
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• pp.250-258
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• 2023

Ceramic oxide layer was formed on the surface of high silicon aluminum alloy by using PEO (plasma electrolytic oxidation) process. The microstructure of the oxide layer was analyzed using scanning electron microscopy (SEM) and x-ray diffraction patterns (XRD). The high silicon aluminum alloy prior to PEO process consists of Al, Si and Al₂Cu phases in XRD analysis, whereas Al₂Cu phase selectively disappeared after PEO treatment. Considerable decrease of relative intensity in most of peaks in XRD results of the high silicon aluminum alloy treated by PEO process was observed. It may be attributed to the formation of amorphous phases after PEO treatment. The corrosion behavior of the high silicon aluminum alloy treated by PEO process was investigated using electrochemical impedance spectroscopy (EIS) and other electrochemical techniques (i.e., open circuit potential and polarization curve). Electroanalytical studies indicated that the high silicon aluminum alloy treated by PEO process shows greater corrosion resistance than that untreated by PEO process.

• Journal of Welding and Joining
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• 제32권3호
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• pp.27-33
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• 2014

This paper presents a brief summary on a relatively new plasma aided electrolytic surface treatment process for light metals. A brief discussion regarding the advantages, principle, process parameters and applications of this process is discussed. The process owes its origin to Sluginov who discovered an arc discharge phenomenon in electrolysis in 1880. A similar process was studied and developed by Markov and coworkers in 1970s who successfully deposited an oxide film on aluminium. Several investigation thereafter lead to the establishment of suitable process parameters for deposition of a crystalline oxide film of more than $100{\mu}m$ thickness on the surface of light metals such as aluminium, titanium and magnesium. This process nowadays goes by several names such as plasma electrolytic oxidation (PEO), micro-arc oxidation (MOA), anodic spark deposition (ASD) etc. Several startups and surface treatment companies have taken up the process and deployed it successfully in a range of products, from military grade rifles to common off road sprockets. However, there are certain limitations to this technology such as the formation of an outer porous oxide layer, especially in case of magnesium which displays a Piling Bedworth ratio of less than one and thus an inherent non protective oxide. This can be treated further but adds to the cost of the process. Overall, it can be said the PEO process offers a better solution than the conventional coating processes. It offers advantages considering the fact that he electrolyte used in PEO process is environmental friendly and the temperature control is not as strict as in case of other surface treatment processes.

• Corrosion Science and Technology
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• 제8권6호
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• pp.227-231
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• 2009

Mg and Mg alloys have been used for lots of applications, including automobile industry, aerospace, mobile phone and computer parts owing to low density. However, Mg and Mg alloys have a restricted application because of poor corrosion properties. Thus, improved surface treatments are required to produce protective films that protect the substrate from corrosive environments. Environmental friendly Plasma Electrolytic Oxidation (PEO) has been widely investigated on magnesium alloys. PEO process combines electrochemical oxidation with plasma treatment in the aqueous solution. In this study, AZ91 Mg alloys were treated by PEO process in controlling the current with PC condition and treated time, concentration of NaF, NaOH, and $Na_2SiO_3$. The surface morphology and phase composition were analyzed using SEM, EDS and XRD. The potentiodynamic polarization tests were carried out for the analysis of corrosion properties of specimen. Additionally, salt spray tests were carried out to examine and compare the corrosion properties of the PEO treated Mg alloys.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.132.2-132.2
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• 2017

플라즈마 전해 산화(Plasma Electrolytic Oxidation, PEO)는 Al, Ti, Mg 합금과 같은 경량 금속소재에 대한 표면처리기술로서 주목을 받고 있다. PEO 처리에 의해 표면에 치밀하게 형성되는 세라믹 산화층은 우수한 내식성, 내마모성을 보유하기 때문에, 이와 같은 특성이 요구되는 분야에 적용하기 위한 연구가 활발하다. 특히 PEO 세라믹 코팅층의 응착마모(adhesive wear)와 절삭마모(abrasive wear)에 관한 연구는 상당부분 이루어지고 있으나, 캐비테이션 침식과 같은 침식마모(erosive wear) 특성에 관한 연구는 부족한 실정이다. 본 연구에서는 알루미늄 합금 소지에 제작된 PEO 코팅층의 캐비테이션 손상 특성을 고찰하였으며, 전해액 조성이 PEO 코팅층의 미세조직과 캐비테이션 손상 특성에 미치는 영향을 살펴보았다. PEO 처리를 위해 사용된 소재는 상용 5083-O합금 판재로서 $2cm{\times}2cm$로 절단하여, 에머리페이퍼로 1000번까지 연마하여 사용하였다. 사용된 전해액은 증류수에 KOH(1 g/L)을 base로 하여 $Na_2SiO_3$(2 g/L)의 첨가유무를 변수로 하였다. 시편을 양극으로 하고 STS304를 음극으로 하여 각각 DC 전원 공급기의 +극과 -극에 연결하였으며, 정전류 조건에서 30분간 $0.1A/cm^2$의 전류밀도를 인가하였다. PEO 처리후 시편은 SEM, EDS, XRD를 이용하여 표면 특성 평가를 실시하였다. PEO코팅층의 캐비테이션 특성 평가는 초음파 진동식 캐비테이션 발생 장치를 이용하였으며, 캐비테이션 실험 후 시간에 따른 표면 거칠기의 변화 거동을 분석하였다.

• 한국표면공학회지
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• 제57권2호
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• pp.86-91
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• 2024

In this study, we investigated the effect of Na₂SiO₃ concentration on the Plasma Electrolytic Oxidation(PEO) film formation of Al6061 alloy. The morphology of the PEO films were examined by Optical Microscope(OM) and Scanning Electron Microscope(SEM). PEO film thickness increases as the Na₂SiO₃ concentration increases. The elemental analysis of PEO films was conducted using Dispersive X-ray Spectrometer(EDS). The cross-sectional elemental analysis result shows that the Si concentration tends to increase as the concentration of Na₂SiO₃ increases. X-Ray Diffraction(XRD) analysis was performed to confirm the degree of phase change according to Na₂SiO₃ concentration. In addition, Vickers hardness was measured to confirm the mechanical strength of the PEO film. As the concentration of Na₂SiO₃ increases, the hardness value also tends to increase.

• 한국재료학회지
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• 제29권10호
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• pp.609-616
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• 2019

Oxide coatings are formed on die-cast AZ91D Mg alloy through an environmentally friendly plasma electrolytic oxidation(PEO) process using an electrolytic solution of $NaAlO_2$, KOH, and KF. The effects of PEO condition with different duty cycles (10 %, 20 %, and 40 %) and frequencies(500 Hz, 1,000 Hz, and 2,000 Hz) on the crystal phase, composition, microstructure, and micro-hardness properties of the oxide coatings are investigated. The oxide coatings on die-cast AZ91D Mg alloy mainly consist of MgO and $MgAl_2O_4$ phases. The proportion of each crystalline phase depends on various electrical parameters, such as duty cycle and frequency. The surfaces of oxide coatings exhibit as craters of pancake-shaped oxide melting and solidification particles. The pore size and surface roughness of the oxide coating increase considerably with increase in the number of duty cycles, while the densification and thickness of oxide coatings increase progressively. Differences in the growth mechanism may be attributed to differences in oxide growth during PEO treatment that occur because the applied operating voltage is insufficient to reach breakdown voltage at higher frequencies. PEO treatment also results in the oxide coating having strong adhesion properties on the Mg alloy. The micro-hardness at the cross-section of oxide coatings is much higher not only compared to that on the surface but also compared to that of the conventional anodizing oxide coatings. The oxide coatings are found to improve the micro-hardness with the increase in the number of duty cycles, which suggests that various electrical parameters, such as duty cycle and frequency, are among the key factors controlling the structural and physical properties of the oxide coating.