Wear and corrosion resistant coatings formed by microarc oxidation on TiAl alloy

Microarc oxidation is an advanced method to fabricate ceramic coatings on valve metals. The coatings up to 110 μm thick were prepared on γ-TiAl alloy by the alternating-current microarc oxidation in silicate electrolyte. Their structures, composition, wear resistance and corrosion resistance were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD), ball-disc dry sliding and electrochemical polarization tests. Results showed that the dense layer of coatings was mainly composed of Al2TiO5 and TiO2 rutile phases, while the loose layer contained a large amount of amorphous SiO2 besides Al2TiO5 and TiO2 rutile phases. Maximum value of microhardness in the coating was about three times higher than that of TiAl substrate. The wear rate of coating was only 1/10 of TiAl substrate. Corrosion current density of the coated TiAl alloy was greatly reduced. The microarc oxidation is a promising method to improve the wear resistance and corrosion resistance of TiAl alloy.