Influence of microstructure of TC4 substrate on the MAO coating

The influence of microstructures of the two TC4 substrates on the growth process and properties of micro-arc oxidation (MAO) coatings were investigated and compared. The morphologies, thickness, roughness and compositions of the coatings on forging-TC4 (F-MAO) and SLM-TC4 (S-MAO) were characterised by scanning electron microscopy, atomic force microscopy, energy-dispersive spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The SLM-TC4 exhibits needles of α′ phase, while forging-TC4 have distinct α and β phases. The results show that α′ phase of SLM-TC4 causes the discharge channels to be uniform during MAO process, making S-MAO free of cracks. The S-MAO coating has smaller pores and lower roughness, but thicker than that of F-MAO coating. S-MAO coating has better corrosion resistance and biological activity than that of F-MAO in SBF.