Preparation and Tribological Properties of Plasma Electrolytic Oxidation Coatings on Carbon Steel

In this paper,oxide coatings on carbon steel were prepared from aluminate and silicate-based electrolytes by plasma electrolytic oxidation (PEO) technique. The microstructure,element content/distribution and phase composition were examined by scanning electron microscope,energy dispersive spectrometer and X-ray diffraction. A reciprocating friction and wear test-rig was used to evaluate the tribological properties of PEO coatings. The wear tracks on PEO coatings and counterpart balls were observed. The results indicate that the PEO coating prepared from aluminate-based electrolyte was mainly composed of Fe₃O₄ and spinel FeAl₂O₄ while the PEO coating prepared from silicate-based electrolyte consisted of amorphous Fe,Si and O. The PEO coating prepared from aluminate-based electrolyte exhibited lower frictional coefficient and wear rate than that of PEO coating prepared from silicate-based electrolyte under dry sliding condition. This is because the Fe₃O₄ in the PEO coating prepared from aluminate-based electrolyte transferred to the counterpart ball and had lubrication and anti-wear function.