MICROSTRUCTURES AND ABRASIVE PROPERTIES OF THE OXIDE COATINGS ON Al6061 ALLOYS PREPARED BY PLASMA ELECTROLYTIC OXIDATION IN DIFFERENT ELECTROLYTES

Al2O3 coatings were prepared on T6-tempered Al6061 alloys substrate under a hybrid voltage (AC 200 V–60 Hz and DC 260 V value) by plasma electrolytic oxidation (PEO) in 30 min. The effects of different electrolytes on the abrasive behaviors of the coatings were studied by conducting dry ball-on-disk wear tests. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the coating microstructure. XRD analysis results show that the coatings mainly consist of α- and γ-Al2O3, and some mullite and AlPO4 phase in Na2SiO3 and Na3PO4 containing electrolytes, respectively. The wear test results show that the coatings which were PEO-treated in Na3PO4 containing electrolyte presented the most excellent abrasive resistance property.