OXIDE BASED CERAMIC COATING ON PURE ZIRCONIUM BY MICROARC OXIDATION METHOD

Abstract

In this study, the surface of pure zirconium was coated by microarc oxidation method under constant electrical parameters and the same electrolytic composition for the duration of 5, 15, 30, 45, 60, 90, 120 minutes. The phase content, surface morphology and microhardness of the formed coatings were characterized by X-ray diffraction, scanning electron microscopy, profilometry and microhardness measurements. The coating was porous in nature and contains significant amount of microcracks. The coating is formed by the crystalline phases of monoclinic (m-ZrO2) and tetragonal (t-ZrO2) zirconium oxide and duration of the process did not affect the phase content. The existence of the silicon in addition to zirconium and oxygen in the coatings was evident. The thickness of the coating increased linearly from 5 mu m to 135 mu m with the increase of the coating duration. The surface roughness was raised from 0.5 mu m to 6.4 mu m with the coating duration. The average coating microhardness was measured as 600 HV compared to the pure zirconium substrate's microhardness of 200 HV and there was no systematical change with the coating duration.