Abstract
The Ti-6Al-4V alloy was treated in concentrated phosphoric acid solution and by powder blasting, respectively, subsequently coated by silica using sol–gel dip-coating technique. A barrier layer of titanium pyrophosphate (TiP2O7) was synthesized at the Ti-6Al-4V substrate surface after the heat treatment. XRD and SEM/EDS analysis revealed that an amorphous silica coating was formed on the alloy. The isothermal and cyclic oxidation behavior of the treated alloy with silica coating and the corresponding bare alloy was investigated at 600 °C in static air to investigate the synergetic effect of the SiO2 coating and surface treatment on the oxidation resistance of the alloy by thermogravimetry. The average parabolic rate constants of the treated specimens with silica coating were greatly reduced. The stratified oxide layer formed on the bare alloy, while thinner oxide layer formed on the treated alloys with silica coating. The oxidation resistance of the present alloy was improved. The effect of silica coating on the microhardness of the substrate was investigated.
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