Effect of Y(NO3)3 doping on the microstructure and wear resistance of AZ91D micro arc oxidation coating

DOI:	10.11809/bqzbgcxb2023.04.028
Keywords:	micro arc oxidation; AZ91D alloy; Y(NO3)3 doping; ceramic coating
Abstract:	In this paper, AZ91D magnesium alloy is modified through micro arc oxidation to obtain ceramic coating with high wear resistance. The aim is to improve the wear resistance of AZ91D magnesium alloy. The effect of the change in Y(NO3)3 doping amount on phase composition, microstructure, surface roughness, microhardness and friction coefficient of the modified coating is studied by introducing rare earth salt Y(NO3)3 doping into Na2SiO3 NaOH system. The results show that the magnesium alloy coating is composed of MgO, MgSiO3 and Mg2SiO4 after the micro arc oxidation treatment in the Na2SiO3 electrolyte system, and the phase content of MgSiO3 in the coating increases after the doping of Y(NO3)3. When the doping amount of Y(NO3)3 exceeds 0.015 mol/L, the typical “crater like” micro pore channels in the micro arc oxidation coating significantly reduces, and the coating surface tends to be smooth. When the concentration of Y(NO3)3 is too high, corrosion pits appear in local areas of the coating. The microhardness of the coating after modification by micro arc oxidation is higher than that of the matrix alloys, especially when the doping amount of Y(NO3)3 exceeds 0.015 mol/L. During these periods, the microhardness of the coating is the highest at about 382.6±7.6 HV1, which is more than 4 times the hardness of the matrix. The friction coefficient of the Y(NO3)3 doped coating decreases first and then increases, and, when the minimum value appears in sample S3, the friction coefficient is within 0.60 to 0.65, which proves an improved wear resistance.
Issue:	Vol. 44 No. 4 (2023)
Published:	2023-04-28
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