Effects of interval of enhancive voltage on micro-arc oxidation coatings of magnesium alloy AZ91D

The effects of interval of enhancive voltage on micro-arc oxidation(MAO)coating of magnesium alloy AZ91D were investigated in silicate electrolyte.The microstructures were studied with TT230 digital coating thickness gauge, JSM-6700F scanning electron microscope, 2206 surface roughness measuring instrument and W-92 Coating adhesion scratch test machine, and the corrosion and wear resistance were assessed by means of CHI660C electrochemistry workstation and UMT-2MT ball-block reciprocating friction tester.The results show that with the increasing of interval of enhancive voltage, all of the thickness, roughness and bonding force of MAO coating always increase.The porosity of the coatings first increases, then decreases;it is up to its maximum values when interval of enhancive voltage is 150 s.The MAO coatings have the better corrosion and wear resistance than matrix metal, which have the best corrosion resistance as interval of enhancive voltage is 150 s and the best wear resistance as enhancive voltage is 60 s.