Journal of the Korean institute of surface engineering (한국표면공학회지)

The Korean Institute of Surface Engineering (한국표면공학회)
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Formation Behavior and Properties of PEO Films on AZ91 Mg Alloy in 0.1 M NaOH + 0.05 M NaF Solution Containing Various Na2SiO3 Concentrations

AZ91 마그네슘 합금의 플라즈마 전해산화 피막 형성 및 물성에 미치는 0.1 M NaOH + 0.05 M NaF 용액 중 Na2SiO3 농도의 영향

  • Kwon, Duyoung (Surface Technology Division, Korea Institute of Materials Science) ;
  • Song, Pung-Keun (Department of Materials Science and Engineering, Pusan National University) ;
  • Moon, Sungmo (Surface Technology Division, Korea Institute of Materials Science)
  • 권두영 (재료연구소 표면기술연구본부 전기화학 연구실) ;
  • 송풍근 (부산대학교 재료공학부) ;
  • 문성모 (재료연구소 표면기술연구본부 전기화학 연구실)
  • Received : 2020.03.05
  • Accepted : 2020.04.26
  • Published : 2020.04.30
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Abstract

Effects of Na2SiO3 concentration added into 0.1 M NaOH + 0.05 M NaF solution on the formation behavior and properties of PEO films on AZ91 Mg alloy were investigated under 1200 Hz of alternating current (AC) by voltage-time curves, in-situ observation of arc generation behavior and measurements of film thickness, surface roughness and micro vickers hardness. In the absence of Na2SiO3 in the 0.1 M NaOH + 0.05 M NaF solution, about 4 ㎛ thick PEO film was formed within 1 min and then PEO film did not grow but white spots were formed by local burning. Addition of Na2SiO3 up to 0.2 M caused more increased formation voltage and growth of PEO film with uniform generation of arcs. Addition of Na2SiO3 from 0.2 M to 0.4 M showed nearly the same voltage-time behavior and uniform arc generation. Addition of Na2SiO3 more than 0.5 M resulted in a decrease of formation voltage and non-uniform arc generation due to local burning. PEO film growth rate increased with increasing added Na2SiO3 concentration but maximum PEO film thickness was limited by local burning if added Na2SiO3 concentration is higher than 0.5 M. Surface roughness of PEO film increased with increasing added Na2SiO3 concentration and appeared to be proportional to the PEO film thickness. PEO film hardness increased with increasing added Na2SiO3 concentration and reached a steady-state value of about 930 HV at more than 0.5 M of added Na2SiO3 concentration.

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References

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