Residual Stresses in Microarc Oxidation Ceramic Coatings on Biocompatible AZ31 Magnesium Alloys

Ceramic coatings have been successfully prepared on biocompatible AZ31 magnesium alloy substrates using microarc oxidation (MAO) technique. Residual stresses attributed to the MgO constituent of the coatings at different oxidation voltages have been evaluated by x-ray diffraction using the sin(2) psi method. It is found that tensile residual stresses were present in the coatings, and they decreased from 1418 to 545 MPa as the oxidation voltages increased from 250 to 350 V. Correlations between the residual stresses and microstructural morphology have been discussed. The residual stress characteristics are attributed to the microcracks and the new phase formation during the MAO process.