Effects of sodium tungstate on characteristics
of microarc oxidation coatings formed on magnesium
alloy in silicate-KOH electrolyte
of microarc oxidation coatings formed on magnesium
alloy in silicate-KOH electrolyte
(1. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics,
Chinese Academy of Sciences, Lanzhou 730000, China;
2. Graduate School of Chinese Academy of Sciences, Beijing 100039, China)
Chinese Academy of Sciences, Lanzhou 730000, China;
2. Graduate School of Chinese Academy of Sciences, Beijing 100039, China)
Abstract: Oxide coatings on AM60B magnesium alloy were prepared using the microarc oxidation(MAO) technique in silicate-KOH electrolyte with addition of 0−6.0 g/L Na2WO4. The MAO processes in base electrolyte with different concentrations of Na2WO4 were studied. The microstructure, compositions and mechanical tribological characteristics of the oxide coatings were also investigated by SEM, XRD, XPS, microhardness analysis and ball-on-disc friction testing, respectively. It is found that the addition of Na2WO4 into the base electrolyte has direct effect on the characteristics of voltage—time curves and breakdown voltage in MAO process. The number of micropores at top of the coating surface is increased by the addition of Na2WO4. The fraction of forsterite Mg2SiO4 in the oxide coating increases with increasing concentration of Na2WO4 in base electrolytes. Furthermore, the microhardness and wear resistance of oxide coatings are enhanced as well.
Key words: magnesium alloy; microarc oxidation; Na2WO4; oxide coating; wear resistance